Rework as esp-idf component

erase(iterator) perf

.appveyor.yml

@@ -1,4 +1,6 @@
-# Copyright 2017 Daniel James
+# Copyright 2016, 2017 Peter Dimov
+# Copyright 2017 - 2019 James E. King III
+# Copyright 2019 - 2021 Alexander Grund
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -6,27 +8,107 @@ version: 1.0.{build}-{branch}
 
 shallow_clone: true
 
+branches:
+  only:
+    - master
+    - develop
+    - /bugfix\/.*/
+    - /feature\/.*/
+    - /fix\/.*/
+    - /pr\/.*/
+
+matrix:
+  fast_finish: false
+  # Adding MAYFAIL to any matrix job allows it to fail but the build stays green:
+  allow_failures:
+    - MAYFAIL: true
+
 environment:
+  global:
+    B2_CI_VERSION: 1
+    GIT_FETCH_JOBS: 4
+    B2_ADDRESS_MODEL: 32,64
+    B2_VARIANT: debug,release
+
   matrix:
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      TOOLSET: msvc-10.0,msvc-11.0,msvc-12.0,msvc-14.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc-14.1
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
-      TOOLSET: msvc-14.2
+    - FLAVOR: Visual Studio 2008, 2010, 2012
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      B2_TOOLSET: msvc-9.0,msvc-10.0,msvc-11.0
+      B2_ADDRESS_MODEL: 32 # No 64bit support
+
+    - FLAVOR: Visual Studio 2013, 2015
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      B2_TOOLSET: msvc-12.0,msvc-14.0
+
+    - FLAVOR: Visual Studio 2017
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      B2_CXXSTD: 14,17,latest
+      B2_TOOLSET: msvc-14.1
+
+    - FLAVOR: cygwin (32-bit)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin\bin;
+      B2_ADDRESS_MODEL: 32
+      B2_CXXSTD: 03,11,14,1z
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (64-bit)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 03,11,14,1z
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (64-bit, latest)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 03,11
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+
+    - FLAVOR: cygwin (64-bit, latest)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 14,1z
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+
+    - FLAVOR: mingw-w64, 32 bit
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin;
+      B2_CXXSTD: 03,11,14,17,2a
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 64 bit
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin;
+      B2_CXXSTD: 03,11,14,17,2a
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 64
+
+    #- FLAVOR: CodeCov (VS 2019)
+    #  APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    #  B2_CXXFLAGS: -permissive-
+    #  B2_CXXSTD: 14
+    #  B2_TOOLSET: msvc-14.2
+    #  COVERAGE: true
 
 install:
-  - set BOOST_ROOT=c:\projects\boost
-  - cd c:\projects\
-  - python %APPVEYOR_BUILD_FOLDER%\ci\download-boost-snapshot.py master
-  - rd /s /q %BOOST_ROOT%\boost\unordered
-  - cd %BOOST_ROOT%\tools\build
-  - cmd /c bootstrap
-  - cd %APPVEYOR_BUILD_FOLDER%
-  - echo. 2>Jamroot.jam
+  - git clone --depth 1 https://github.com/boostorg/boost-ci.git C:\boost-ci-cloned
+  # Copy ci folder if not testing Boost.CI
+  - if NOT "%APPVEYOR_PROJECT_NAME%" == "boost-ci" xcopy /s /e /q /i /y C:\boost-ci-cloned\ci .\ci
+  - rmdir /s /q C:\boost-ci-cloned
+  - ci\appveyor\install.bat
 
 build: off
 
-test_script:
-  - cd %APPVEYOR_BUILD_FOLDER%\test
-  - cmd /c %BOOST_ROOT%\tools\build\b2 -j 3 toolset=%TOOLSET% include=%APPVEYOR_BUILD_FOLDER%\include include=%BOOST_ROOT%
+test_script: ci\build.bat
+
+for:
+  # CodeCov coverage build
+  - matrix:
+      only: [COVERAGE: true]
+    test_script: [ps: ci\codecov.ps1]

.codecov.yml

@@ -0,0 +1,23 @@
+# Copyright 2019 - 2021 Alexander Grund
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
+#
+# Sample codecov configuration file. Edit as required
+
+codecov:
+  max_report_age: off
+  require_ci_to_pass: yes
+  notify:
+    # Increase this if you have multiple coverage collection jobs
+    after_n_builds: 1
+    wait_for_ci: yes
+
+# Change how pull request comments look
+comment:
+  layout: "reach,diff,flags,files,footer"
+
+# Ignore specific files or folders. Glob patterns are supported.
+# See https://docs.codecov.com/docs/ignoring-paths
+ignore:
+  - extra/**/*
+  # - test/**/*

.drone.jsonnet

@@ -0,0 +1,180 @@
+# Copyright 2022 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+local library = "unordered";
+
+local triggers =
+{
+    branch: [ "master", "develop", "feature/*", "bugfix/*" ]
+};
+
+local ubsan = { UBSAN: '1', UBSAN_OPTIONS: 'print_stacktrace=1' };
+local asan = { ASAN: '1' };
+
+local linux_pipeline(name, image, environment, packages = "", sources = [], arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "docker",
+    trigger: triggers,
+    platform:
+    {
+        os: "linux",
+        arch: arch
+    },
+    steps:
+    [
+        {
+            name: "everything",
+            image: image,
+            environment: environment,
+            commands:
+            [
+                'set -e',
+                'wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -',
+            ] +
+            (if sources != [] then [ ('apt-add-repository "' + source + '"') for source in sources ] else []) +
+            (if packages != "" then [ 'apt-get update', 'apt-get -y install ' + packages ] else []) +
+            [
+                'export LIBRARY=' + library,
+                './.drone/drone.sh',
+            ]
+        }
+    ]
+};
+
+local macos_pipeline(name, environment, xcode_version = "12.2", osx_version = "catalina", arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "exec",
+    trigger: triggers,
+    platform: {
+        "os": "darwin",
+        "arch": arch
+    },
+    node: {
+        "os": osx_version
+    },
+    steps: [
+        {
+            name: "everything",
+            environment: environment + { "DEVELOPER_DIR": "/Applications/Xcode-" + xcode_version + ".app/Contents/Developer" },
+            commands:
+            [
+                'export LIBRARY=' + library,
+                './.drone/drone.sh',
+            ]
+        }
+    ]
+};
+
+local windows_pipeline(name, image, environment, arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "docker",
+    trigger: triggers,
+    platform:
+    {
+        os: "windows",
+        arch: arch
+    },
+    "steps":
+    [
+        {
+            name: "everything",
+            image: image,
+            environment: environment,
+            commands:
+            [
+                'cmd /C .drone\\\\drone.bat ' + library,
+            ]
+        }
+    ]
+};
+
+[
+    linux_pipeline(
+        "Linux 14.04 GCC 4.4 32/64",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.4', CXXSTD: '98,0x', ADDRMD: '32,64' },
+        "g++-4.4-multilib",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.6 32/64",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.6', CXXSTD: '98,0x', ADDRMD: '32,64' },
+        "g++-4.6-multilib",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.7 32/64",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.7', CXXSTD: '98,0x', ADDRMD: '32,64' },
+        "g++-4.7-multilib",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.8* 32/64",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.9 32/64",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '03,11', ADDRMD: '32,64' },
+        "g++-4.9-multilib",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* ARM64 32",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32' },
+        arch="arm64",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* ARM64 64",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '64' },
+        arch="arm64",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* S390x 32",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32' },
+        arch="s390x",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* S390x 64",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '64' },
+        arch="s390x",
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 ASAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + asan,
+    ),
+
+    windows_pipeline(
+        "Windows VS2017 msvc-14.1",
+        "cppalliance/dronevs2017",
+        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17,latest' },
+    ),
+]

.drone/drone.bat

@@ -0,0 +1,23 @@
+@REM Copyright 2022 Peter Dimov
+@REM Distributed under the Boost Software License, Version 1.0.
+@REM https://www.boost.org/LICENSE_1_0.txt
+
+@ECHO ON
+
+set LIBRARY=%1
+set DRONE_BUILD_DIR=%CD%
+
+set BOOST_BRANCH=develop
+if "%DRONE_BRANCH%" == "master" set BOOST_BRANCH=master
+cd ..
+git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+cd boost-root
+git submodule update --init tools/boostdep
+xcopy /s /e /q %DRONE_BUILD_DIR% libs\%LIBRARY%\
+python tools/boostdep/depinst/depinst.py %LIBRARY%
+cmd /c bootstrap
+b2 -d0 headers
+
+if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
+if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
+b2 -j3 libs/%LIBRARY%/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release embed-manifest-via=linker

.drone/drone.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Copyright 2022 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+set -ex
+
+DRONE_BUILD_DIR=$(pwd)
+
+BOOST_BRANCH=develop
+if [ "$DRONE_BRANCH" = "master" ]; then BOOST_BRANCH=master; fi
+
+cd ..
+git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+cd boost-root
+git submodule update --init tools/boostdep
+cp -r $DRONE_BUILD_DIR/* libs/$LIBRARY
+python tools/boostdep/depinst/depinst.py $LIBRARY
+./bootstrap.sh
+./b2 -d0 headers
+
+echo "using $TOOLSET : : $COMPILER ;" > ~/user-config.jam
+./b2 -j3 libs/$LIBRARY/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${ADDRMD:+address-model=$ADDRMD} ${UBSAN:+undefined-sanitizer=norecover debug-symbols=on} ${ASAN:+address-sanitizer=norecover debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}

.github/workflows/ci.yml

@@ -0,0 +1,397 @@
+# Copyright 2020-2021 Peter Dimov
+# Copyright 2021 Andrey Semashev
+# Copyright 2021 Alexander Grund
+# Copyright 2022 James E. King III
+#
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
+---
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - develop
+      - bugfix/**
+      - feature/**
+      - fix/**
+      - pr/**
+
+concurrency:
+  group: ${{format('{0}:{1}', github.repository, github.ref)}}
+  cancel-in-progress: true
+
+env:
+  GIT_FETCH_JOBS: 8
+  NET_RETRY_COUNT: 5
+  B2_CI_VERSION: 1
+  B2_VARIANT: debug,release
+  LCOV_BRANCH_COVERAGE: 0
+  CODECOV_NAME: Github Actions
+
+jobs:
+  posix:
+    defaults:
+      run:
+        shell: bash
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Linux, gcc
+          - { compiler: gcc-4.8,   cxxstd: '03,11',          os: ubuntu-18.04, install: 'g++-4.8-multilib', address-model: '32,64' }
+          - { compiler: gcc-4.9,   cxxstd: '03,11',          os: ubuntu-20.04, container: 'ubuntu:16.04' }
+          - { compiler: gcc-5,     cxxstd: '03,11,14,1z',    os: ubuntu-18.04, install: 'g++-5-multilib', address-model: '32,64' }
+          - { compiler: gcc-6,     cxxstd: '03,11,14,17',    os: ubuntu-18.04, install: 'g++-6-multilib', address-model: '32,64' }
+          - { compiler: gcc-7,     cxxstd: '03,11,14,17',    os: ubuntu-18.04, install: 'g++-7-multilib', address-model: '32,64' }
+          - { compiler: gcc-8,     cxxstd: '03,11,14,17,2a', os: ubuntu-18.04, install: 'g++-8-multilib', address-model: '32,64' }
+          - { compiler: gcc-9,     cxxstd: '03,11,14,17,2a', os: ubuntu-18.04, install: 'g++-9-multilib', address-model: '32,64' }
+          - { compiler: gcc-10,    cxxstd: '03,11,14,17,20', os: ubuntu-20.04, install: 'g++-10-multilib', address-model: '32,64' }
+          - { compiler: gcc-11,    cxxstd: '03,11,14,17,20', os: ubuntu-20.04, install: 'g++-11-multilib', address-model: '32,64' }
+          - { compiler: gcc-12,    cxxstd: '03,11,14,17,20', os: ubuntu-22.04, install: 'g++-12-multilib', address-model: '32,64' }
+          - { name: GCC w/ sanitizers, sanitize: yes,
+              compiler: gcc-12,    cxxstd: '03,11,14,17,20', os: ubuntu-22.04 }
+          - { name: Collect coverage, coverage: yes,
+              compiler: gcc-8,     cxxstd: '03,11',          os: ubuntu-20.04, install: 'g++-8-multilib', address-model: '32,64' }
+
+          # Linux, clang
+          - { compiler: clang-3.7, cxxstd: '03,11,14',       os: ubuntu-20.04, container: 'ubuntu:16.04' }
+          - { compiler: clang-3.8, cxxstd: '03,11,14',       os: ubuntu-20.04, container: 'ubuntu:16.04' }
+          - { compiler: clang-3.9, cxxstd: '03,11,14',       os: ubuntu-18.04 }
+          - { compiler: clang-4.0, cxxstd: '03,11,14',       os: ubuntu-18.04 }
+          - { compiler: clang-5.0, cxxstd: '03,11,14,1z',    os: ubuntu-18.04 }
+          - { compiler: clang-6.0, cxxstd: '03,11,14,17',    os: ubuntu-18.04 }
+          - { compiler: clang-7,   cxxstd: '03,11,14,17',    os: ubuntu-18.04 }
+          - { compiler: clang-8,   cxxstd: '03,11,14,17',    os: ubuntu-18.04 }
+          - { compiler: clang-9,   cxxstd: '03,11,14,17,2a', os: ubuntu-20.04 }
+          - { compiler: clang-10,  cxxstd: '03,11,14,17,20', os: ubuntu-20.04 }
+          - { compiler: clang-11,  cxxstd: '03,11,14,17,20', os: ubuntu-20.04 }
+          - { compiler: clang-12,  cxxstd: '03,11,14,17,20', os: ubuntu-20.04 }
+          - { compiler: clang-13,  cxxstd: '03,11,14,17,20', os: ubuntu-22.04 }
+          - { compiler: clang-14,  cxxstd: '03,11,14,17,20', os: ubuntu-22.04 }
+
+          # libc++
+          - { compiler: clang-6.0, cxxstd: '03,11,14',       os: ubuntu-18.04, stdlib: libc++, install: 'clang-6.0 libc++-dev libc++abi-dev' }
+          - { compiler: clang-12,  cxxstd: '03,11,14,17,20', os: ubuntu-20.04, stdlib: libc++, install: 'clang-12 libc++-12-dev libc++abi-12-dev' }
+          - { name: Clang w/ sanitizers, sanitize: yes,
+              compiler: clang-12,  cxxstd: '03,11,14,17,20', os: ubuntu-20.04, stdlib: libc++, install: 'clang-12 libc++-12-dev libc++abi-12-dev' }
+
+          # OSX, clang
+          - { compiler: clang,     cxxstd: '03,11,14,17,2a', os: macos-11, sanitize: yes }
+
+    timeout-minutes: 120
+    runs-on: ${{matrix.os}}
+    container: ${{matrix.container}}
+    env: {B2_USE_CCACHE: 1}
+
+    steps:
+      - name: Setup environment
+        run: |
+            if [ -f "/etc/debian_version" ]; then
+                echo "DEBIAN_FRONTEND=noninteractive" >> $GITHUB_ENV
+                export DEBIAN_FRONTEND=noninteractive
+            fi
+            if [ -n "${{matrix.container}}" ] && [ -f "/etc/debian_version" ]; then
+                apt-get -o Acquire::Retries=$NET_RETRY_COUNT update
+                apt-get -o Acquire::Retries=$NET_RETRY_COUNT install -y sudo software-properties-common
+                # Need (newer) git, and the older Ubuntu container may require requesting the key manually using port 80
+                apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys E1DD270288B4E6030699E45FA1715D88E1DF1F24
+                for i in {1..${NET_RETRY_COUNT:-3}}; do sudo -E add-apt-repository -y ppa:git-core/ppa && break || sleep 10; done
+                apt-get -o Acquire::Retries=$NET_RETRY_COUNT update
+                apt-get -o Acquire::Retries=$NET_RETRY_COUNT install -y g++ python libpython-dev git
+            fi
+            # For jobs not compatible with ccache, use "ccache: no" in the matrix
+            if [[ "${{ matrix.ccache }}" == "no" ]]; then
+                echo "B2_USE_CCACHE=0" >> $GITHUB_ENV
+            fi
+            git config --global pack.threads 0
+
+      - uses: actions/checkout@v3
+        with:
+          # For coverage builds fetch the whole history, else only 1 commit using a 'fake ternary'
+          fetch-depth: ${{ matrix.coverage && '0' || '1' }}
+
+      - name: Cache ccache
+        uses: actions/cache@v3
+        if: env.B2_USE_CCACHE
+        with:
+          path: ~/.ccache
+          key: ${{matrix.os}}-${{matrix.container}}-${{matrix.compiler}}-${{github.sha}}
+          restore-keys: ${{matrix.os}}-${{matrix.container}}-${{matrix.compiler}}-
+
+      - name: Fetch Boost.CI
+        uses: actions/checkout@v3
+        with:
+          repository: boostorg/boost-ci
+          ref: master
+          path: boost-ci-cloned
+
+      - name: Get CI scripts folder
+        run: |
+            # Copy ci folder if not testing Boost.CI
+            [[ "$GITHUB_REPOSITORY" =~ "boost-ci" ]] || cp -r boost-ci-cloned/ci .
+            rm -rf boost-ci-cloned
+
+      - name: Install packages
+        if: startsWith(matrix.os, 'ubuntu')
+        run: |
+            SOURCE_KEYS=(${{join(matrix.source_keys, ' ')}})
+            SOURCES=(${{join(matrix.sources, ' ')}})
+            # Add this by default
+            SOURCES+=(ppa:ubuntu-toolchain-r/test)
+            for key in "${SOURCE_KEYS[@]}"; do
+                for i in {1..$NET_RETRY_COUNT}; do
+                    wget -O - "$key" | sudo apt-key add - && break || sleep 10
+                done
+            done
+            for source in "${SOURCES[@]}"; do
+                for i in {1..$NET_RETRY_COUNT}; do
+                    sudo add-apt-repository $source && break || sleep 10
+                done
+            done
+            sudo apt-get -o Acquire::Retries=$NET_RETRY_COUNT update
+            if [[ -z "${{matrix.install}}" ]]; then
+                pkgs="${{matrix.compiler}}"
+                pkgs="${pkgs/gcc-/g++-}"
+            else
+                pkgs="${{matrix.install}}"
+            fi
+            sudo apt-get -o Acquire::Retries=$NET_RETRY_COUNT install -y $pkgs
+
+      - name: Setup GCC Toolchain
+        if: matrix.gcc_toolchain
+        run: |
+            GCC_TOOLCHAIN_ROOT="$HOME/gcc-toolchain"
+            echo "GCC_TOOLCHAIN_ROOT=$GCC_TOOLCHAIN_ROOT" >> $GITHUB_ENV
+            MULTIARCH_TRIPLET="$(dpkg-architecture -qDEB_HOST_MULTIARCH)"
+            mkdir -p "$GCC_TOOLCHAIN_ROOT"
+            ln -s /usr/include "$GCC_TOOLCHAIN_ROOT/include"
+            ln -s /usr/bin "$GCC_TOOLCHAIN_ROOT/bin"
+            mkdir -p "$GCC_TOOLCHAIN_ROOT/lib/gcc/$MULTIARCH_TRIPLET"
+            ln -s "/usr/lib/gcc/$MULTIARCH_TRIPLET/${{matrix.gcc_toolchain}}" "$GCC_TOOLCHAIN_ROOT/lib/gcc/$MULTIARCH_TRIPLET/${{matrix.gcc_toolchain}}"
+
+      - name: Setup multiarch
+        if: matrix.multiarch
+        run: |
+          sudo apt-get install --no-install-recommends -y binfmt-support qemu-user-static
+          sudo docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+          git clone https://github.com/jeking3/bdde.git
+          echo "$(pwd)/bdde/bin/linux" >> ${GITHUB_PATH}
+          echo "BDDE_DISTRO=${{ matrix.distro }}" >> ${GITHUB_ENV}
+          echo "BDDE_EDITION=${{ matrix.edition }}" >> ${GITHUB_ENV}
+          echo "BDDE_ARCH=${{ matrix.arch }}" >> ${GITHUB_ENV}
+          echo "B2_WRAPPER=bdde" >> ${GITHUB_ENV}
+
+      - name: Setup Boost
+        env:
+          B2_ADDRESS_MODEL: ${{matrix.address-model}}
+          B2_COMPILER: ${{matrix.compiler}}
+          B2_CXXSTD: ${{matrix.cxxstd}}
+          B2_SANITIZE: ${{matrix.sanitize}}
+          B2_STDLIB: ${{matrix.stdlib}}
+          # More entries can be added in the same way, see the B2_ARGS assignment in ci/enforce.sh for the possible keys.
+          # B2_DEFINES: ${{matrix.defines}}
+          # Variables set here (to non-empty) will override the top-level environment variables, e.g.
+          # B2_VARIANT: ${{matrix.variant}}
+        run: source ci/github/install.sh
+
+      - name: Setup coverage collection
+        if: matrix.coverage
+        run: ci/github/codecov.sh "setup"
+
+      - name: Run tests
+        if: '!matrix.coverity'
+        run: ci/build.sh
+
+      - name: Upload coverage
+        if: matrix.coverage
+        run: ci/codecov.sh "upload"
+
+      - name: Run coverity
+        if: matrix.coverity && github.event_name == 'push' && (github.ref_name == 'develop' || github.ref_name == 'master')
+        run: ci/github/coverity.sh
+        env:
+          COVERITY_SCAN_NOTIFICATION_EMAIL: ${{ secrets.COVERITY_SCAN_NOTIFICATION_EMAIL }}
+          COVERITY_SCAN_TOKEN: ${{ secrets.COVERITY_SCAN_TOKEN }}
+
+  windows:
+    defaults:
+      run:
+        shell: cmd
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { toolset: msvc-14.0, cxxstd: '14,latest',       addrmd: '32,64', os: windows-2019 }
+          - { toolset: msvc-14.2, cxxstd: '14,17,20,latest', addrmd: '32,64', os: windows-2019 }
+          - { toolset: msvc-14.3, cxxstd: '14,17,20,latest', addrmd: '32,64', os: windows-2022 }
+          - { toolset: clang-win, cxxstd: '14,17,latest',    addrmd: '32,64', os: windows-2022 }
+          - { toolset: gcc,       cxxstd: '03,11,14,17,2a',  addrmd: '64',    os: windows-2019 }
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Fetch Boost.CI
+        uses: actions/checkout@v3
+        with:
+          repository: boostorg/boost-ci
+          ref: master
+          path: boost-ci-cloned
+      - name: Get CI scripts folder
+        run: |
+            REM Copy ci folder if not testing Boost.CI
+            if "%GITHUB_REPOSITORY%" == "%GITHUB_REPOSITORY:boost-ci=%" xcopy /s /e /q /i /y boost-ci-cloned\ci .\ci
+            rmdir /s /q boost-ci-cloned
+
+      - name: Setup Boost
+        run: ci\github\install.bat
+
+      - name: Run tests
+        if: '!matrix.coverage'
+        run: ci\build.bat
+        env:
+          B2_TOOLSET: ${{matrix.toolset}}
+          B2_CXXSTD: ${{matrix.cxxstd}}
+          B2_ADDRESS_MODEL: ${{matrix.addrmd}}
+
+      - name: Collect coverage
+        shell: powershell
+        if: matrix.coverage
+        run: ci\opencppcoverage.ps1
+        env:
+          B2_TOOLSET: ${{matrix.toolset}}
+          B2_CXXSTD: ${{matrix.cxxstd}}
+          B2_ADDRESS_MODEL: ${{matrix.addrmd}}
+
+      - name: Upload coverage
+        if: matrix.coverage
+        uses: codecov/codecov-action@v2
+        with:
+          files: __out/cobertura.xml
+
+  MSYS2:
+    defaults:
+      run:
+        shell: msys2 {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { sys: MINGW32, compiler: gcc, cxxstd: '03,11,17,20' }
+          - { sys: MINGW64, compiler: gcc, cxxstd: '03,11,17,20' }
+
+    runs-on: windows-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup MSYS2 environment
+        uses: msys2/setup-msys2@v2
+        with:
+          msystem: ${{matrix.sys}}
+          update: true
+          install: git python
+          pacboy: gcc:p cmake:p ninja:p
+
+      - name: Fetch Boost.CI
+        uses: actions/checkout@v3
+        with:
+          repository: boostorg/boost-ci
+          ref: master
+          path: boost-ci-cloned
+      - name: Get CI scripts folder
+        run: |
+            # Copy ci folder if not testing Boost.CI
+            [[ "$GITHUB_REPOSITORY" =~ "boost-ci" ]] || cp -r boost-ci-cloned/ci .
+            rm -rf boost-ci-cloned
+
+      - name: Setup Boost
+        env:
+          B2_COMPILER: ${{matrix.compiler}}
+          B2_CXXSTD: ${{matrix.cxxstd}}
+          B2_SANITIZE: ${{matrix.sanitize}}
+          B2_STDLIB: ${{matrix.stdlib}}
+        run: ci/github/install.sh
+
+      - name: Run tests
+        run: ci/build.sh
+
+      # Run also the CMake tests to avoid having to setup another matrix for CMake on MSYS
+      - name: Run CMake tests
+        run: |
+            cd "$BOOST_ROOT"
+            mkdir __build_cmake_test__ && cd __build_cmake_test__
+            cmake -G Ninja -DCMAKE_BUILD_TYPE=Debug -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=ON -DBUILD_TESTING=ON -DBoost_VERBOSE=ON ..
+            cmake --build . --target tests --config Debug -j$B2_JOBS
+            ctest --output-on-failure --build-config Debug
+
+  CMake:
+    defaults:
+      run:
+        shell: bash
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { os: ubuntu-20.04, build_shared: ON,  build_type: Debug, generator: 'Unix Makefiles' }
+          - { os: windows-2019, build_shared: ON,  build_type: Debug, generator: 'Visual Studio 16 2019' }
+
+    timeout-minutes: 120
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Fetch Boost.CI
+        uses: actions/checkout@v3
+        with:
+          repository: boostorg/boost-ci
+          ref: master
+          path: boost-ci-cloned
+      - name: Get CI scripts folder
+        run: |
+            # Copy ci folder if not testing Boost.CI
+            [[ "$GITHUB_REPOSITORY" =~ "boost-ci" ]] || cp -r boost-ci-cloned/ci .
+            rm -rf boost-ci-cloned
+      - name: Setup Boost
+        env: {B2_DONT_BOOTSTRAP: 1}
+        run: source ci/github/install.sh
+
+      - name: Run CMake tests
+        run: |
+            cd "$BOOST_ROOT"
+            mkdir __build_cmake_test__ && cd __build_cmake_test__
+            cmake -G "${{matrix.generator}}" -DCMAKE_BUILD_TYPE=${{matrix.build_type}} -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=${{matrix.build_shared}} -DBUILD_TESTING=ON -DBoost_VERBOSE=ON ..
+            cmake --build . --target tests --config ${{matrix.build_type}} -j$B2_JOBS
+            ctest --output-on-failure --build-config ${{matrix.build_type}}
+
+      - name: Run CMake subdir tests
+        run: |
+            cmake_test_folder="$BOOST_ROOT/libs/$SELF/test/cmake_test" # New unified folder
+            [ -d "$cmake_test_folder" ] || cmake_test_folder="$BOOST_ROOT/libs/$SELF/test/cmake_subdir_test"
+            cd "$cmake_test_folder"
+            mkdir __build_cmake_subdir_test__ && cd __build_cmake_subdir_test__
+            cmake -G "${{matrix.generator}}" -DBOOST_CI_INSTALL_TEST=OFF -DCMAKE_BUILD_TYPE=${{matrix.build_type}} -DBUILD_SHARED_LIBS=${{matrix.build_shared}} ..
+            cmake --build . --config ${{matrix.build_type}} -j$B2_JOBS
+            ctest --output-on-failure --build-config ${{matrix.build_type}}
+
+      - name: Install Library
+        run: |
+            cd "$BOOST_ROOT"
+            mkdir __build_cmake_install_test__ && cd __build_cmake_install_test__
+            cmake -G "${{matrix.generator}}" -DCMAKE_BUILD_TYPE=${{matrix.build_type}} -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=${{matrix.build_shared}} -DCMAKE_INSTALL_PREFIX=~/.local -DBoost_VERBOSE=ON -DBoost_DEBUG=ON ..
+            cmake --build . --target install --config ${{matrix.build_type}} -j$B2_JOBS
+      - name: Run CMake install tests
+        run: |
+            cmake_test_folder="$BOOST_ROOT/libs/$SELF/test/cmake_test" # New unified folder
+            [ -d "$cmake_test_folder" ] || cmake_test_folder="$BOOST_ROOT/libs/$SELF/test/cmake_install_test"
+            cd "$cmake_test_folder"
+            mkdir __build_cmake_install_test__ && cd __build_cmake_install_test__
+            cmake -G "${{matrix.generator}}" -DBOOST_CI_INSTALL_TEST=ON -DCMAKE_BUILD_TYPE=${{matrix.build_type}} -DBUILD_SHARED_LIBS=${{matrix.build_shared}} -DCMAKE_PREFIX_PATH=~/.local ..
+            cmake --build . --config ${{matrix.build_type}} -j$B2_JOBS
+            ctest --output-on-failure --build-config ${{matrix.build_type}}

CMakeLists.txt

@@ -1,9 +1,11 @@
 # Generated by `boostdep --cmake unordered`
-# Copyright 2020 Peter Dimov
+# Copyright 2020, 2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required(VERSION 3.5...3.16)
+if(NOT DEFINED IDF_TARGET)
+
+cmake_minimum_required(VERSION 3.5...3.20)
 
 project(boost_unordered VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
@@ -16,14 +18,12 @@ target_link_libraries(boost_unordered
   INTERFACE
     Boost::assert
     Boost::config
-    Boost::container
     Boost::container_hash
     Boost::core
-    Boost::detail
     Boost::move
+    Boost::mp11
     Boost::predef
     Boost::preprocessor
-    Boost::smart_ptr
     Boost::throw_exception
     Boost::tuple
     Boost::type_traits
@@ -35,3 +35,27 @@ if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
 
 endif()
 
+else()
+
+FILE(GLOB_RECURSE headers include/*.h include/*.hpp)
+
+idf_component_register(
+    SRCS
+        ${headers}
+    INCLUDE_DIRS
+        include
+    REQUIRES
+        boost_assert
+        boost_config
+        boost_container_hash
+        boost_core
+        boost_move
+        boost_mp11
+        boost_predef
+        boost_preprocessor
+        boost_throw_exception
+        boost_tuple
+        boost_type_traits
+)
+
+endif()

LICENSE

@@ -0,0 +1,23 @@
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

README.md

@@ -0,0 +1,49 @@
+# Boost.Unordered
+
+Part of collection of the [Boost C++ Libraries](http://github.com/boostorg).
+
+For accessing data based on key lookup, the C++ standard library offers `std::set`, `std::map`, `std::multiset` and `std::multimap`.
+These are generally implemented using balanced binary trees so that lookup time has logarithmic complexity.
+That is generally okay, but in many cases a hash table can perform better, as accessing data has constant complexity, on average.
+The worst case complexity is linear, but that occurs rarely and with some care, can be avoided.
+
+Also, the existing containers require a 'less than' comparison object to order their elements.
+For some data types this is impossible to implement or isn’t practical.
+In contrast, a hash table only needs an equality function and a hash function for the key.
+
+With this in mind, unordered associative containers were added to the C++ standard.
+This is an implementation of the containers described in C++11, with some deviations from the standard in order to work with non-C++11 compilers and libraries.
+
+
+### License
+
+Distributed under the [Boost Software License, Version 1.0](http://www.boost.org/LICENSE_1_0.txt).
+
+### Properties
+
+* C++03
+* Header-Only
+
+### Build Status
+
+Branch          | GH Actions | Appveyor | codecov.io | Deps | Docs | Tests |
+:-------------: | ---------- | -------- | ---------- | ---- | ---- | ----- |
+[`master`](https://github.com/boostorg/unordered/tree/master)   | [![CI](https://github.com/boostorg/unordered/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/boostorg/unordered/actions/workflows/ci.yml)  | [![Build status](https://ci.appveyor.com/api/projects/status/github/boostorg/unordered?branch=master&svg=true)](https://ci.appveyor.com/project/danieljames/unordered-qtwe6/branch/master)   | [![codecov](https://codecov.io/gh/boostorg/unordered/branch/master/graph/badge.svg)](https://codecov.io/gh/boostorg/unordered/branch/master)   | [![Deps](https://img.shields.io/badge/deps-master-brightgreen.svg)](https://pdimov.github.io/boostdep-report/master/unordered.html)   | [![Documentation](https://img.shields.io/badge/docs-master-brightgreen.svg)](https://www.boost.org/doc/libs/master/libs/unordered/doc/html/unordered.html)   | [![Enter the Matrix](https://img.shields.io/badge/matrix-master-brightgreen.svg)](http://www.boost.org/development/tests/master/developer/unordered.html)
+[`develop`](https://github.com/boostorg/unordered/tree/develop) | [![CI](https://github.com/boostorg/unordered/actions/workflows/ci.yml/badge.svg?branch=develop)](https://github.com/boostorg/unordered/actions/workflows/ci.yml) | [![Build status](https://ci.appveyor.com/api/projects/status/github/boostorg/unordered?branch=develop&svg=true)](https://ci.appveyor.com/project/danieljames/unordered-qtwe6/branch/develop) | [![codecov](https://codecov.io/gh/boostorg/unordered/branch/develop/graph/badge.svg)](https://codecov.io/gh/boostorg/unordered/branch/develop) | [![Deps](https://img.shields.io/badge/deps-develop-brightgreen.svg)](https://pdimov.github.io/boostdep-report/develop/unordered.html) | [![Documentation](https://img.shields.io/badge/docs-develop-brightgreen.svg)](https://www.boost.org/doc/libs/develop/libs/unordered/doc/html/unordered.html) | [![Enter the Matrix](https://img.shields.io/badge/matrix-develop-brightgreen.svg)](http://www.boost.org/development/tests/develop/developer/unordered.html)
+
+### Directories
+
+| Name        | Purpose                        |
+| ----------- | ------------------------------ |
+| `doc`       | documentation                  |
+| `example`   | examples                       |
+| `include`   | headers                        |
+| `test`      | unit tests                     |
+
+### More information
+
+* [Ask questions](http://stackoverflow.com/questions/ask?tags=c%2B%2B,boost,boost-unordered)
+* [Report bugs](https://github.com/boostorg/unordered/issues): Be sure to mention Boost version, platform and compiler you're using. A small compilable code sample to reproduce the problem is always good as well.
+* Submit your patches as pull requests against **develop** branch. Note that by submitting patches you agree to license your modifications under the [Boost Software License, Version 1.0](http://www.boost.org/LICENSE_1_0.txt).
+* Discussions about the library are held on the [Boost developers mailing list](http://www.boost.org/community/groups.html#main). Be sure to read the [discussion policy](http://www.boost.org/community/policy.html) before posting and add the `[unordered]` tag at the beginning of the subject line.
+

benchmark/string.cpp

@@ -0,0 +1,488 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/config.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_TSL_HOPSCOTCH
+# include "tsl/hopscotch_map.h"
+#endif
+#ifdef HAVE_TSL_ROBIN
+# include "tsl/robin_map.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::uint32_t s, std::size_t size )
+{
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << label << ": " << ( t2 - t1 ) / 1ms << " ms (s=" << s << ", size=" << size << ")\n";
+
+    t1 = t2;
+}
+
+constexpr unsigned N = 2'000'000;
+constexpr int K = 10;
+
+static std::vector<std::string> indices1, indices2;
+
+static std::string make_index( unsigned x )
+{
+    char buffer[ 64 ];
+    std::snprintf( buffer, sizeof(buffer), "pfx_%u_sfx", x );
+
+    return buffer;
+}
+
+static std::string make_random_index( unsigned x )
+{
+    char buffer[ 64 ];
+    std::snprintf( buffer, sizeof(buffer), "pfx_%0*d_%u_sfx", x % 8 + 1, 0, x );
+
+    return buffer;
+}
+
+static void init_indices()
+{
+    indices1.reserve( N*2+1 );
+    indices1.push_back( make_index( 0 ) );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices1.push_back( make_index( i ) );
+    }
+
+    indices2.reserve( N*2+1 );
+    indices2.push_back( make_index( 0 ) );
+
+    {
+        boost::detail::splitmix64 rng;
+
+        for( unsigned i = 1; i <= N*2; ++i )
+        {
+            indices2.push_back( make_random_index( static_cast<std::uint32_t>( rng() ) ) );
+        }
+    }
+}
+
+template<class Map> BOOST_NOINLINE void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices1[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices2[ i ], i } );
+    }
+
+    print_time( t1, "Random insert",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_lookup( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::uint32_t s;
+    
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices1[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices2[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Random lookup",  s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    auto it = map.begin();
+
+    while( it != map.end() )
+    {
+        if( it->second & 1 )
+        {
+            if constexpr( std::is_void_v< decltype( map.erase( it ) ) > )
+            {
+                map.erase( it++ );
+            }
+            else
+            {
+                it = map.erase( it );
+            }
+        }
+        else
+        {
+            ++it;
+        }
+    }
+
+    print_time( t1, "Iterate and erase odd elements",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_erase( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices1[ i ] );
+    }
+
+    print_time( t1, "Consecutive erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices2[ i ] );
+    }
+
+    print_time( t1, "Random erase",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+// counting allocator
+
+static std::size_t s_alloc_bytes = 0;
+static std::size_t s_alloc_count = 0;
+
+template<class T> struct allocator
+{
+    using value_type = T;
+
+    allocator() = default;
+
+    template<class U> allocator( allocator<U> const & ) noexcept
+    {
+    }
+
+    template<class U> bool operator==( allocator<U> const & ) const noexcept
+    {
+        return true;
+    }
+
+    template<class U> bool operator!=( allocator<U> const& ) const noexcept
+    {
+        return false;
+    }
+
+    T* allocate( std::size_t n ) const
+    {
+        s_alloc_bytes += n * sizeof(T);
+        s_alloc_count++;
+
+        return std::allocator<T>().allocate( n );
+    }
+
+    void deallocate( T* p, std::size_t n ) const noexcept
+    {
+        s_alloc_bytes -= n * sizeof(T);
+        s_alloc_count--;
+
+        std::allocator<T>().deallocate( p, n );
+    }
+};
+
+//
+
+struct record
+{
+    std::string label_;
+    long long time_;
+    std::size_t bytes_;
+    std::size_t count_;
+};
+
+static std::vector<record> times;
+
+template<template<class...> class Map> BOOST_NOINLINE void test( char const* label )
+{
+    std::cout << label << ":\n\n";
+
+    s_alloc_bytes = 0;
+    s_alloc_count = 0;
+
+    Map<std::string, std::uint32_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_insert( map, t1 );
+
+    std::cout << "Memory: " << s_alloc_bytes << " bytes in " << s_alloc_count << " allocations\n\n";
+
+    record rec = { label, 0, s_alloc_bytes, s_alloc_count };
+
+    test_lookup( map, t1 );
+    test_iteration( map, t1 );
+    test_lookup( map, t1 );
+    test_erase( map, t1 );
+
+    auto tN = std::chrono::steady_clock::now();
+    std::cout << "Total: " << ( tN - t0 ) / 1ms << " ms\n\n";
+
+    rec.time_ = ( tN - t0 ) / 1ms;
+    times.push_back( rec );
+}
+
+// multi_index emulation of unordered_map
+
+template<class K, class V> struct pair
+{
+    K first;
+    mutable V second;
+};
+
+using namespace boost::multi_index;
+
+template<class K, class V> using multi_index_map = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first> >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+// aliases using the counting allocator
+
+template<class K, class V> using allocator_for = ::allocator< std::pair<K const, V> >;
+
+template<class K, class V> using std_unordered_map =
+    std::unordered_map<K, V, std::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map =
+    boost::unordered_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map =
+    absl::node_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map =
+    absl::flat_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map =
+    tsl::hopscotch_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map =
+    tsl::hopscotch_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map =
+    tsl::robin_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map =
+    tsl::robin_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+// fnv1a_hash
+
+template<int Bits> struct fnv1a_hash_impl;
+
+template<> struct fnv1a_hash_impl<32>
+{
+    std::size_t operator()( std::string const& s ) const
+    {
+        std::size_t h = 0x811C9DC5u;
+
+        char const * first = s.data();
+        char const * last = first + s.size();
+
+        for( ; first != last; ++first )
+        {
+            h ^= static_cast<unsigned char>( *first );
+            h *= 0x01000193ul;
+        }
+
+        return h;
+    }
+};
+
+template<> struct fnv1a_hash_impl<64>
+{
+    std::size_t operator()( std::string const& s ) const
+    {
+        std::size_t h = 0xCBF29CE484222325ull;
+
+        char const * first = s.data();
+        char const * last = first + s.size();
+
+        for( ; first != last; ++first )
+        {
+            h ^= static_cast<unsigned char>( *first );
+            h *= 0x00000100000001B3ull;
+        }
+
+        return h;
+    }
+};
+
+struct fnv1a_hash: fnv1a_hash_impl< std::numeric_limits<std::size_t>::digits > {};
+
+template<class K, class V> using std_unordered_map_fnv1a =
+std::unordered_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map_fnv1a =
+    boost::unordered_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using multi_index_map_fnv1a = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first>, fnv1a_hash >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map_fnv1a =
+    absl::node_hash_map<K, V, fnv1a_hash, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map_fnv1a =
+    absl::flat_hash_map<K, V, fnv1a_hash, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map_fnv1a =
+    tsl::hopscotch_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map_fnv1a =
+    tsl::hopscotch_pg_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map_fnv1a =
+    tsl::robin_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map_fnv1a =
+    tsl::robin_pg_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+//
+
+int main()
+{
+    init_indices();
+
+#if 0
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<multi_index_map>( "multi_index_map" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map>( "tsl::hopscotch_map" );
+    test<tsl_hopscotch_pg_map>( "tsl::hopscotch_pg_map" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map>( "tsl::robin_map" );
+    test<tsl_robin_pg_map>( "tsl::robin_pg_map" );
+
+#endif
+
+#endif
+
+    test<std_unordered_map_fnv1a>( "std::unordered_map, FNV-1a" );
+    test<boost_unordered_map_fnv1a>( "boost::unordered_map, FNV-1a" );
+    test<multi_index_map_fnv1a>( "multi_index_map, FNV-1a" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map_fnv1a>( "absl::node_hash_map, FNV-1a" );
+    test<absl_flat_hash_map_fnv1a>( "absl::flat_hash_map, FNV-1a" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map_fnv1a>( "tsl::hopscotch_map, FNV-1a" );
+    test<tsl_hopscotch_pg_map_fnv1a>( "tsl::hopscotch_pg_map, FNV-1a" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map_fnv1a>( "tsl::robin_map, FNV-1a" );
+    test<tsl_robin_pg_map_fnv1a>( "tsl::robin_pg_map, FNV-1a" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 31 ) << ( x.label_ + ": " ) << std::setw( 5 ) << x.time_ << " ms, " << std::setw( 9 ) << x.bytes_ << " bytes in " << x.count_ << " allocations\n";
+    }
+}
+
+#ifdef HAVE_ABSEIL
+# include "absl/container/internal/raw_hash_set.cc"
+# include "absl/hash/internal/hash.cc"
+# include "absl/hash/internal/low_level_hash.cc"
+# include "absl/hash/internal/city.cc"
+#endif

benchmark/string_view.cpp

@@ -0,0 +1,489 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/config.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_TSL_HOPSCOTCH
+# include "tsl/hopscotch_map.h"
+#endif
+#ifdef HAVE_TSL_ROBIN
+# include "tsl/robin_map.h"
+#endif
+#include <unordered_map>
+#include <string_view>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::uint32_t s, std::size_t size )
+{
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << label << ": " << ( t2 - t1 ) / 1ms << " ms (s=" << s << ", size=" << size << ")\n";
+
+    t1 = t2;
+}
+
+constexpr unsigned N = 2'000'000;
+constexpr int K = 10;
+
+static std::vector<std::string> indices1, indices2;
+
+static std::string make_index( unsigned x )
+{
+    char buffer[ 64 ];
+    std::snprintf( buffer, sizeof(buffer), "pfx_%u_sfx", x );
+
+    return buffer;
+}
+
+static std::string make_random_index( unsigned x )
+{
+    char buffer[ 64 ];
+    std::snprintf( buffer, sizeof(buffer), "pfx_%0*d_%u_sfx", x % 8 + 1, 0, x );
+
+    return buffer;
+}
+
+static void init_indices()
+{
+    indices1.reserve( N*2+1 );
+    indices1.push_back( make_index( 0 ) );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices1.push_back( make_index( i ) );
+    }
+
+    indices2.reserve( N*2+1 );
+    indices2.push_back( make_index( 0 ) );
+
+    {
+        boost::detail::splitmix64 rng;
+
+        for( unsigned i = 1; i <= N*2; ++i )
+        {
+            indices2.push_back( make_random_index( static_cast<std::uint32_t>( rng() ) ) );
+        }
+    }
+}
+
+template<class Map> BOOST_NOINLINE void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices1[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices2[ i ], i } );
+    }
+
+    print_time( t1, "Random insert",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_lookup( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::uint32_t s;
+    
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices1[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices2[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Random lookup",  s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    auto it = map.begin();
+
+    while( it != map.end() )
+    {
+        if( it->second & 1 )
+        {
+            if constexpr( std::is_void_v< decltype( map.erase( it ) ) > )
+            {
+                map.erase( it++ );
+            }
+            else
+            {
+                it = map.erase( it );
+            }
+        }
+        else
+        {
+            ++it;
+        }
+    }
+
+    print_time( t1, "Iterate and erase odd elements",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_erase( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices1[ i ] );
+    }
+
+    print_time( t1, "Consecutive erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices2[ i ] );
+    }
+
+    print_time( t1, "Random erase",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+// counting allocator
+
+static std::size_t s_alloc_bytes = 0;
+static std::size_t s_alloc_count = 0;
+
+template<class T> struct allocator
+{
+    using value_type = T;
+
+    allocator() = default;
+
+    template<class U> allocator( allocator<U> const & ) noexcept
+    {
+    }
+
+    template<class U> bool operator==( allocator<U> const & ) const noexcept
+    {
+        return true;
+    }
+
+    template<class U> bool operator!=( allocator<U> const& ) const noexcept
+    {
+        return false;
+    }
+
+    T* allocate( std::size_t n ) const
+    {
+        s_alloc_bytes += n * sizeof(T);
+        s_alloc_count++;
+
+        return std::allocator<T>().allocate( n );
+    }
+
+    void deallocate( T* p, std::size_t n ) const noexcept
+    {
+        s_alloc_bytes -= n * sizeof(T);
+        s_alloc_count--;
+
+        std::allocator<T>().deallocate( p, n );
+    }
+};
+
+//
+
+struct record
+{
+    std::string label_;
+    long long time_;
+    std::size_t bytes_;
+    std::size_t count_;
+};
+
+static std::vector<record> times;
+
+template<template<class...> class Map> BOOST_NOINLINE void test( char const* label )
+{
+    std::cout << label << ":\n\n";
+
+    s_alloc_bytes = 0;
+    s_alloc_count = 0;
+
+    Map<std::string_view, std::uint32_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_insert( map, t1 );
+
+    std::cout << "Memory: " << s_alloc_bytes << " bytes in " << s_alloc_count << " allocations\n\n";
+
+    record rec = { label, 0, s_alloc_bytes, s_alloc_count };
+
+    test_lookup( map, t1 );
+    test_iteration( map, t1 );
+    test_lookup( map, t1 );
+    test_erase( map, t1 );
+
+    auto tN = std::chrono::steady_clock::now();
+    std::cout << "Total: " << ( tN - t0 ) / 1ms << " ms\n\n";
+
+    rec.time_ = ( tN - t0 ) / 1ms;
+    times.push_back( rec );
+}
+
+// multi_index emulation of unordered_map
+
+template<class K, class V> struct pair
+{
+    K first;
+    mutable V second;
+};
+
+using namespace boost::multi_index;
+
+template<class K, class V> using multi_index_map = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first> >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+// aliases using the counting allocator
+
+template<class K, class V> using allocator_for = ::allocator< std::pair<K const, V> >;
+
+template<class K, class V> using std_unordered_map =
+    std::unordered_map<K, V, std::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map =
+    boost::unordered_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map =
+    absl::node_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map =
+    absl::flat_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map =
+    tsl::hopscotch_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map =
+    tsl::hopscotch_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map =
+    tsl::robin_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map =
+    tsl::robin_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+// fnv1a_hash
+
+template<int Bits> struct fnv1a_hash_impl;
+
+template<> struct fnv1a_hash_impl<32>
+{
+    std::size_t operator()( std::string_view const& s ) const
+    {
+        std::size_t h = 0x811C9DC5u;
+
+        char const * first = s.data();
+        char const * last = first + s.size();
+
+        for( ; first != last; ++first )
+        {
+            h ^= static_cast<unsigned char>( *first );
+            h *= 0x01000193ul;
+        }
+
+        return h;
+    }
+};
+
+template<> struct fnv1a_hash_impl<64>
+{
+    std::size_t operator()( std::string_view const& s ) const
+    {
+        std::size_t h = 0xCBF29CE484222325ull;
+
+        char const * first = s.data();
+        char const * last = first + s.size();
+
+        for( ; first != last; ++first )
+        {
+            h ^= static_cast<unsigned char>( *first );
+            h *= 0x00000100000001B3ull;
+        }
+
+        return h;
+    }
+};
+
+struct fnv1a_hash: fnv1a_hash_impl< std::numeric_limits<std::size_t>::digits > {};
+
+template<class K, class V> using std_unordered_map_fnv1a =
+std::unordered_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map_fnv1a =
+    boost::unordered_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using multi_index_map_fnv1a = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first>, fnv1a_hash >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map_fnv1a =
+    absl::node_hash_map<K, V, fnv1a_hash, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map_fnv1a =
+    absl::flat_hash_map<K, V, fnv1a_hash, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map_fnv1a =
+    tsl::hopscotch_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map_fnv1a =
+    tsl::hopscotch_pg_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map_fnv1a =
+    tsl::robin_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map_fnv1a =
+    tsl::robin_pg_map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+//
+
+int main()
+{
+    init_indices();
+
+#if 0
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<multi_index_map>( "multi_index_map" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map>( "tsl::hopscotch_map" );
+    test<tsl_hopscotch_pg_map>( "tsl::hopscotch_pg_map" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map>( "tsl::robin_map" );
+    test<tsl_robin_pg_map>( "tsl::robin_pg_map" );
+
+#endif
+
+#endif
+
+    test<std_unordered_map_fnv1a>( "std::unordered_map, FNV-1a" );
+    test<boost_unordered_map_fnv1a>( "boost::unordered_map, FNV-1a" );
+    test<multi_index_map_fnv1a>( "multi_index_map, FNV-1a" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map_fnv1a>( "absl::node_hash_map, FNV-1a" );
+    test<absl_flat_hash_map_fnv1a>( "absl::flat_hash_map, FNV-1a" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map_fnv1a>( "tsl::hopscotch_map, FNV-1a" );
+    test<tsl_hopscotch_pg_map_fnv1a>( "tsl::hopscotch_pg_map, FNV-1a" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map_fnv1a>( "tsl::robin_map, FNV-1a" );
+    test<tsl_robin_pg_map_fnv1a>( "tsl::robin_pg_map, FNV-1a" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 31 ) << ( x.label_ + ": " ) << std::setw( 5 ) << x.time_ << " ms, " << std::setw( 9 ) << x.bytes_ << " bytes in " << x.count_ << " allocations\n";
+    }
+}
+
+#ifdef HAVE_ABSEIL
+# include "absl/container/internal/raw_hash_set.cc"
+# include "absl/hash/internal/hash.cc"
+# include "absl/hash/internal/low_level_hash.cc"
+# include "absl/hash/internal/city.cc"
+#endif

benchmark/uint32.cpp

@@ -0,0 +1,386 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/endian/conversion.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/config.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_TSL_HOPSCOTCH
+# include "tsl/hopscotch_map.h"
+#endif
+#ifdef HAVE_TSL_ROBIN
+# include "tsl/robin_map.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::uint32_t s, std::size_t size )
+{
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << label << ": " << ( t2 - t1 ) / 1ms << " ms (s=" << s << ", size=" << size << ")\n";
+
+    t1 = t2;
+}
+
+constexpr unsigned N = 2'000'000;
+constexpr int K = 10;
+
+static std::vector< std::uint32_t > indices1, indices2, indices3;
+
+static void init_indices()
+{
+    indices1.push_back( 0 );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices1.push_back( i );
+    }
+
+    indices2.push_back( 0 );
+
+    {
+        boost::detail::splitmix64 rng;
+
+        for( unsigned i = 1; i <= N*2; ++i )
+        {
+            indices2.push_back( static_cast<std::uint32_t>( rng() ) );
+        }
+    }
+
+    indices3.push_back( 0 );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices3.push_back( boost::endian::endian_reverse( static_cast<std::uint32_t>( i ) ) );
+    }
+}
+
+template<class Map> BOOST_NOINLINE void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices1[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices2[ i ], i } );
+    }
+
+    print_time( t1, "Random insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices3[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive reversed insert",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_lookup( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::uint32_t s;
+    
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices1[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices2[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Random lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices3[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive reversed lookup",  s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    auto it = map.begin();
+
+    while( it != map.end() )
+    {
+        if( it->second & 1 )
+        {
+            if constexpr( std::is_void_v< decltype( map.erase( it ) ) > )
+            {
+                map.erase( it++ );
+            }
+            else
+            {
+                it = map.erase( it );
+            }
+        }
+        else
+        {
+            ++it;
+        }
+    }
+
+    print_time( t1, "Iterate and erase odd elements",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_erase( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices1[ i ] );
+    }
+
+    print_time( t1, "Consecutive erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices2[ i ] );
+    }
+
+    print_time( t1, "Random erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices3[ i ] );
+    }
+
+    print_time( t1, "Consecutive reversed erase",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+// counting allocator
+
+static std::size_t s_alloc_bytes = 0;
+static std::size_t s_alloc_count = 0;
+
+template<class T> struct allocator
+{
+    using value_type = T;
+
+    allocator() = default;
+
+    template<class U> allocator( allocator<U> const & ) noexcept
+    {
+    }
+
+    template<class U> bool operator==( allocator<U> const & ) const noexcept
+    {
+        return true;
+    }
+
+    template<class U> bool operator!=( allocator<U> const& ) const noexcept
+    {
+        return false;
+    }
+
+    T* allocate( std::size_t n ) const
+    {
+        s_alloc_bytes += n * sizeof(T);
+        s_alloc_count++;
+
+        return std::allocator<T>().allocate( n );
+    }
+
+    void deallocate( T* p, std::size_t n ) const noexcept
+    {
+        s_alloc_bytes -= n * sizeof(T);
+        s_alloc_count--;
+
+        std::allocator<T>().deallocate( p, n );
+    }
+};
+
+//
+
+struct record
+{
+    std::string label_;
+    long long time_;
+    std::size_t bytes_;
+    std::size_t count_;
+};
+
+static std::vector<record> times;
+
+template<template<class...> class Map> BOOST_NOINLINE void test( char const* label )
+{
+    std::cout << label << ":\n\n";
+
+    s_alloc_bytes = 0;
+    s_alloc_count = 0;
+
+    Map<std::uint32_t, std::uint32_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_insert( map, t1 );
+
+    std::cout << "Memory: " << s_alloc_bytes << " bytes in " << s_alloc_count << " allocations\n\n";
+
+    record rec = { label, 0, s_alloc_bytes, s_alloc_count };
+
+    test_lookup( map, t1 );
+    test_iteration( map, t1 );
+    test_lookup( map, t1 );
+    test_erase( map, t1 );
+
+    auto tN = std::chrono::steady_clock::now();
+    std::cout << "Total: " << ( tN - t0 ) / 1ms << " ms\n\n";
+
+    rec.time_ = ( tN - t0 ) / 1ms;
+    times.push_back( rec );
+}
+
+// multi_index emulation of unordered_map
+
+template<class K, class V> struct pair
+{
+    K first;
+    mutable V second;
+};
+
+using namespace boost::multi_index;
+
+template<class K, class V> using multi_index_map = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first> >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+// aliases using the counting allocator
+
+template<class K, class V> using allocator_for = ::allocator< std::pair<K const, V> >;
+
+template<class K, class V> using std_unordered_map =
+    std::unordered_map<K, V, std::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map =
+    boost::unordered_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map =
+    absl::node_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map =
+    absl::flat_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map =
+    tsl::hopscotch_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map =
+    tsl::hopscotch_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map =
+    tsl::robin_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map =
+    tsl::robin_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+int main()
+{
+    init_indices();
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<multi_index_map>( "multi_index_map" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map>( "tsl::hopscotch_map" );
+    test<tsl_hopscotch_pg_map>( "tsl::hopscotch_pg_map" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map>( "tsl::robin_map" );
+    test<tsl_robin_pg_map>( "tsl::robin_pg_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 25 ) << ( x.label_ + ": " ) << std::setw( 5 ) << x.time_ << " ms, " << std::setw( 9 ) << x.bytes_ << " bytes in " << x.count_ << " allocations\n";
+    }
+}
+
+#ifdef HAVE_ABSEIL
+# include "absl/container/internal/raw_hash_set.cc"
+# include "absl/hash/internal/hash.cc"
+# include "absl/hash/internal/low_level_hash.cc"
+# include "absl/hash/internal/city.cc"
+#endif

benchmark/uint64.cpp

@@ -0,0 +1,386 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/endian/conversion.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/config.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_TSL_HOPSCOTCH
+# include "tsl/hopscotch_map.h"
+#endif
+#ifdef HAVE_TSL_ROBIN
+# include "tsl/robin_map.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::uint64_t s, std::size_t size )
+{
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << label << ": " << ( t2 - t1 ) / 1ms << " ms (s=" << s << ", size=" << size << ")\n";
+
+    t1 = t2;
+}
+
+constexpr unsigned N = 2'000'000;
+constexpr int K = 10;
+
+static std::vector< std::uint64_t > indices1, indices2, indices3;
+
+static void init_indices()
+{
+    indices1.push_back( 0 );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices1.push_back( i );
+    }
+
+    indices2.push_back( 0 );
+
+    {
+        boost::detail::splitmix64 rng;
+
+        for( unsigned i = 1; i <= N*2; ++i )
+        {
+            indices2.push_back( rng() );
+        }
+    }
+
+    indices3.push_back( 0 );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices3.push_back( boost::endian::endian_reverse( static_cast<std::uint64_t>( i ) ) );
+    }
+}
+
+template<class Map> BOOST_NOINLINE void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices1[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices2[ i ], i } );
+    }
+
+    print_time( t1, "Random insert",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.insert( { indices3[ i ], i } );
+    }
+
+    print_time( t1, "Consecutive reversed insert",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_lookup( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::uint64_t s;
+    
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices1[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices2[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Random lookup",  s, map.size() );
+
+    s = 0;
+
+    for( int j = 0; j < K; ++j )
+    {
+        for( unsigned i = 1; i <= N * 2; ++i )
+        {
+            auto it = map.find( indices3[ i ] );
+            if( it != map.end() ) s += it->second;
+        }
+    }
+
+    print_time( t1, "Consecutive reversed lookup",  s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    auto it = map.begin();
+
+    while( it != map.end() )
+    {
+        if( it->second & 1 )
+        {
+            if constexpr( std::is_void_v< decltype( map.erase( it ) ) > )
+            {
+                map.erase( it++ );
+            }
+            else
+            {
+                it = map.erase( it );
+            }
+        }
+        else
+        {
+            ++it;
+        }
+    }
+
+    print_time( t1, "Iterate and erase odd elements",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_erase( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices1[ i ] );
+    }
+
+    print_time( t1, "Consecutive erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices2[ i ] );
+    }
+
+    print_time( t1, "Random erase",  0, map.size() );
+
+    for( unsigned i = 1; i <= N; ++i )
+    {
+        map.erase( indices3[ i ] );
+    }
+
+    print_time( t1, "Consecutive reversed erase",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+// counting allocator
+
+static std::size_t s_alloc_bytes = 0;
+static std::size_t s_alloc_count = 0;
+
+template<class T> struct allocator
+{
+    using value_type = T;
+
+    allocator() = default;
+
+    template<class U> allocator( allocator<U> const & ) noexcept
+    {
+    }
+
+    template<class U> bool operator==( allocator<U> const & ) const noexcept
+    {
+        return true;
+    }
+
+    template<class U> bool operator!=( allocator<U> const& ) const noexcept
+    {
+        return false;
+    }
+
+    T* allocate( std::size_t n ) const
+    {
+        s_alloc_bytes += n * sizeof(T);
+        s_alloc_count++;
+
+        return std::allocator<T>().allocate( n );
+    }
+
+    void deallocate( T* p, std::size_t n ) const noexcept
+    {
+        s_alloc_bytes -= n * sizeof(T);
+        s_alloc_count--;
+
+        std::allocator<T>().deallocate( p, n );
+    }
+};
+
+//
+
+struct record
+{
+    std::string label_;
+    long long time_;
+    std::size_t bytes_;
+    std::size_t count_;
+};
+
+static std::vector<record> times;
+
+template<template<class...> class Map> BOOST_NOINLINE void test( char const* label )
+{
+    std::cout << label << ":\n\n";
+
+    s_alloc_bytes = 0;
+    s_alloc_count = 0;
+
+    Map<std::uint64_t, std::uint64_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_insert( map, t1 );
+
+    std::cout << "Memory: " << s_alloc_bytes << " bytes in " << s_alloc_count << " allocations\n\n";
+
+    record rec = { label, 0, s_alloc_bytes, s_alloc_count };
+
+    test_lookup( map, t1 );
+    test_iteration( map, t1 );
+    test_lookup( map, t1 );
+    test_erase( map, t1 );
+
+    auto tN = std::chrono::steady_clock::now();
+    std::cout << "Total: " << ( tN - t0 ) / 1ms << " ms\n\n";
+
+    rec.time_ = ( tN - t0 ) / 1ms;
+    times.push_back( rec );
+}
+
+// multi_index emulation of unordered_map
+
+template<class K, class V> struct pair
+{
+    K first;
+    mutable V second;
+};
+
+using namespace boost::multi_index;
+
+template<class K, class V> using multi_index_map = multi_index_container<
+  pair<K, V>,
+  indexed_by<
+    hashed_unique< member<pair<K, V>, K, &pair<K, V>::first> >
+  >,
+  ::allocator< pair<K, V> >
+>;
+
+// aliases using the counting allocator
+
+template<class K, class V> using allocator_for = ::allocator< std::pair<K const, V> >;
+
+template<class K, class V> using std_unordered_map =
+    std::unordered_map<K, V, std::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_map =
+    boost::unordered_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+#ifdef HAVE_ABSEIL
+
+template<class K, class V> using absl_node_hash_map =
+    absl::node_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+template<class K, class V> using absl_flat_hash_map =
+    absl::flat_hash_map<K, V, absl::container_internal::hash_default_hash<K>, absl::container_internal::hash_default_eq<K>, allocator_for<K, V>>;
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+template<class K, class V> using tsl_hopscotch_map =
+    tsl::hopscotch_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_hopscotch_pg_map =
+    tsl::hopscotch_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+template<class K, class V> using tsl_robin_map =
+    tsl::robin_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+template<class K, class V> using tsl_robin_pg_map =
+    tsl::robin_pg_map<K, V, std::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+int main()
+{
+    init_indices();
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<multi_index_map>( "multi_index_map" );
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+#ifdef HAVE_TSL_HOPSCOTCH
+
+    test<tsl_hopscotch_map>( "tsl::hopscotch_map" );
+    test<tsl_hopscotch_pg_map>( "tsl::hopscotch_pg_map" );
+
+#endif
+
+#ifdef HAVE_TSL_ROBIN
+
+    test<tsl_robin_map>( "tsl::robin_map" );
+    test<tsl_robin_pg_map>( "tsl::robin_pg_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 25 ) << ( x.label_ + ": " ) << std::setw( 5 ) << x.time_ << " ms, " << std::setw( 9 ) << x.bytes_ << " bytes in " << x.count_ << " allocations\n";
+    }
+}
+
+#ifdef HAVE_ABSEIL
+# include "absl/container/internal/raw_hash_set.cc"
+# include "absl/hash/internal/hash.cc"
+# include "absl/hash/internal/low_level_hash.cc"
+# include "absl/hash/internal/city.cc"
+#endif

ci/download-boost-snapshot.py

@@ -1,66 +0,0 @@
-#!/usr/bin/env python
-
-import urllib, os, os.path, sys, json, tarfile, zipfile, tempfile
-
-def download(snapshot):
-    if snapshot == 'stable':
-        # TODO: Default version/filename if not available?
-        downloads = [
-            "https://sourceforge.net/projects/boost/files/boost/%s/%s.tar.bz2/download" %
-                (os.environ['BOOST_VERSION'], os.environ['BOOST_FILENAME'])]
-    else:
-        json_response = urllib.urlopen('https://api.bintray.com/packages/boostorg/%s/snapshot/files' % (snapshot))
-        x = json.load(json_response)
-
-        extension_priorities = { '.bz2': 2, '.gz': 1, '.zip': 0 }
-        file_list = []
-        version_dates = {}
-        for file in x:
-            file_extension = os.path.splitext(file['path'])[1]
-            if (file_extension in extension_priorities):
-                file['priority'] = extension_priorities[file_extension]
-                file_list.append(file)
-                if not file['version'] in version_dates or file['created'] < version_dates[file['version']]:
-                    version_dates[file['version']] = file['created']
-        file_list.sort(key=lambda x: (version_dates[x['version']], x['priority']), reverse=True)
-        downloads = ['http://dl.bintray.com/boostorg/%s/%s' % (snapshot, file['path']) for file in file_list]
-
-    filename = ''
-    for download_url in downloads:
-        try:
-            print "Downloading: " + download_url
-            (filename, headers) = urllib.urlretrieve(download_url)
-
-            print "Extracting: " + filename
-            dir = tempfile.mkdtemp()
-            extract(filename, dir)
-            os.remove(filename)
-            files = os.listdir(dir)
-            assert(len(files) == 1)
-            os.rename(os.path.join(dir, files[0]), 'boost')
-            return
-        except IOError:
-            print "Error opening URL: " + download_url
-
-def extract(filename, path = '.'):
-    if (filename.endswith(".gz")):
-        tar = tarfile.open(filename, "r:gz")
-        tar.extractall(path)
-        tar.close
-    elif (filename.endswith(".bz2")):
-        tar = tarfile.open(filename, "r:bz2")
-        tar.extractall(path)
-        tar.close
-    elif (filename.endswith(".zip")):
-        zip = zipfile.ZipFile(filename, "r")
-        zip.extractall(path)
-        zip.close
-    else:
-        assert False
-
-if len(sys.argv) == 1:
-    download('stable')
-elif len(sys.argv) == 2:
-    download(sys.argv[1])
-else:
-    print "Usage: %s [stable|branch-name]" % (sys.argv[0])

doc/Jamfile.v2

@@ -1,72 +1,21 @@
-
 # Copyright 2005 Daniel James.
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-using boostbook ;
-using quickbook ;
+import asciidoctor ;
 
-path-constant images_location : ../ ;
-path-constant admonishment_location : ../../../../doc/src/images ;
+html unordered.html : unordered.adoc ;
 
-xml unordered : unordered.qbk :
-    <xsl:param>generate.consistent.ids=1 ;
+install html_ : unordered.html : <location>html ;
 
-boostbook standalone : unordered :
-    <xsl:param>chunk.first.sections=1
-    <xsl:param>chunk.section.depth=2
-    <xsl:param>generate.section.toc.level=2
-    <xsl:param>toc.section.depth=1
-    <xsl:param>toc.max.depth=1
+pdf unordered.pdf : unordered.adoc ;
+explicit unordered.pdf ;
 
-    <xsl:param>boost.compact.typedef=0
-    <xsl:param>boost.compact.function=0
-    <xsl:param>boost.compact.enum=0
-
-    <xsl:param>generate.consistent.ids=1
-
-    # HTML Options:
-
-    <format>html:<xsl:param>boost.root=../../../..
-    <format>html:<xsl:param>img.src.path=../../../../doc/html/
-    <format>xhtml:<xsl:param>boost.root=../../../..
-    <format>xhtml:<xsl:param>img.src.path=../../../../doc/html/
-
-    # PDF Options:
-
-    # TOC Generation: this is needed for FOP-0.9 and later:
-    <xsl:param>fop1.extensions=0
-    <format>pdf:<xsl:param>xep.extensions=1
-    # TOC generation: this is needed for FOP 0.2, but must not be set to zero for FOP-0.9!
-    <format>pdf:<xsl:param>fop.extensions=0
-    # No indent on body text:
-    <format>pdf:<xsl:param>body.start.indent=0pt
-    # Margin size:
-    <format>pdf:<xsl:param>page.margin.inner=0.5in
-    # Margin size:
-    <format>pdf:<xsl:param>page.margin.outer=0.5in
-    # Paper type = A4
-    <format>pdf:<xsl:param>paper.type=A4
-    # Yes, we want graphics for admonishments:
-    <xsl:param>admon.graphics=1
-    # Set this one for PDF generation *only*:
-    # default png graphics are awful in PDF form,
-    # better use SVG's instead:
-    <format>pdf:<xsl:param>admon.graphics.extension=".svg"
-    <format>pdf:<xsl:param>use.role.for.mediaobject=1
-    <format>pdf:<xsl:param>preferred.mediaobject.role=print
-    <format>pdf:<xsl:param>img.src.path=$(images_location)/
-    #<format>pdf:<xsl:param>admon.graphics.path=$(admonishment_location)
-    <format>pdf:<xsl:param>draft.mode="no"
-    <format>pdf:<xsl:param>boost.url.prefix=http://www.boost.org/doc/libs/release/libs/unordered/doc/html
-    ;
+install pdf_ : unordered.pdf : <location>pdf ;
+explicit pdf_ ;
 
 ###############################################################################
-alias boostdoc
-    : unordered
-    :
-    :
-    : ;
+alias boostdoc ;
 explicit boostdoc ;
-alias boostrelease ;
+alias boostrelease : html_ ;
 explicit boostrelease ;

doc/bibliography.xml

@@ -1,26 +0,0 @@
-<!--
-Copyright Daniel James 2008-2009
-Distributed under the Boost Software License, Version 1.0. (See accompanying
-file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
--->
-<section id="unordered.bibliography">
-<title>Bibliography</title>
-<bibliography>
-  <biblioentry>
-    <biblioset relation="journal">
-      <title>C/C++ Users Journal</title>
-      <date>February, 2006</date>
-    </biblioset>
-    <biblioset relation="article">
-      <authorgroup>
-        <author>
-          <firstname>Pete</firstname>
-          <surname>Becker</surname>
-        </author>
-      </authorgroup>
-      <title><ulink url="http://www.ddj.com/cpp/184402066">STL and TR1: Part III - Unordered containers</ulink></title>
-    </biblioset>
-    <para>An introducation to the standard unordered containers.</para>
-  </biblioentry>
-</bibliography>
-</section>

doc/buckets.qbk

@@ -1,168 +0,0 @@
-[/ Copyright 2006-2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[section:buckets The Data Structure]
-
-The containers are made up of a number of 'buckets', each of which can contain
-any number of elements. For example, the following diagram shows an [classref
-boost::unordered_set unordered_set] with 7 buckets containing 5 elements, `A`,
-`B`, `C`, `D` and `E` (this is just for illustration, containers will typically
-have more buckets).
-
-[diagram buckets]
-
-In order to decide which bucket to place an element in, the container applies
-the hash function, `Hash`, to the element's key (for `unordered_set` and
-`unordered_multiset` the key is the whole element, but is referred to as the key
-so that the same terminology can be used for sets and maps). This returns a
-value of type `std::size_t`.  `std::size_t` has a much greater range of values
-then the number of buckets, so the container applies another transformation to
-that value to choose a bucket to place the element in.
-
-Retrieving the elements for a given key is simple. The same process is applied
-to the key to find the correct bucket. Then the key is compared with the
-elements in the bucket to find any elements that match (using the equality
-predicate `Pred`).  If the hash function has worked well the elements will be
-evenly distributed amongst the buckets so only a small number of elements will
-need to be examined.
-
-There is [link unordered.hash_equality more information on hash functions and
-equality predicates in the next section].
-
-You can see in the diagram that `A` & `D` have been placed in the same bucket.
-When looking for elements in this bucket up to 2 comparisons are made, making
-the search slower. This is known as a collision. To keep things fast we try to
-keep collisions to a minimum.
-
-'''
-<table frame="all"><title>Methods for Accessing Buckets</title>
-  <tgroup cols="2">
-    <thead><row>
-      <entry><para>Method</para></entry>
-      <entry><para>Description</para></entry>
-    </row></thead>
-    <tbody>
-      <row>
-       <entry>'''`size_type bucket_count() const`'''</entry>
-       <entry>'''The number of buckets.'''</entry>
-      </row>
-      <row>
-        <entry>'''`size_type max_bucket_count() const`'''</entry>
-        <entry>'''An upper bound on the number of buckets.'''</entry>
-      </row>
-      <row>
-        <entry>'''`size_type bucket_size(size_type n) const`'''</entry>
-        <entry>'''The number of elements in bucket `n`.'''</entry>
-      </row>
-      <row>
-        <entry>'''`size_type bucket(key_type const& k) const`'''</entry>
-        <entry>'''Returns the index of the bucket which would contain `k`.'''</entry>
-      </row>
-      <row>
-        <entry>'''`local_iterator begin(size_type n);`'''</entry>
-        <entry morerows='5'>'''Return begin and end iterators for bucket `n`.'''</entry>
-      </row>
-      <row>
-        <entry>'''`local_iterator end(size_type n);`'''</entry>
-      </row>
-      <row>
-        <entry>'''`const_local_iterator begin(size_type n) const;`'''</entry>
-      </row>
-      <row>
-        <entry>'''`const_local_iterator end(size_type n) const;`'''</entry>
-      </row>
-      <row>
-        <entry>'''`const_local_iterator cbegin(size_type n) const;`'''</entry>
-      </row>
-      <row>
-        <entry>'''`const_local_iterator cend(size_type n) const;`'''</entry>
-      </row>
-    </tbody>
-  </tgroup>
-</table>
-'''
-
-[h2 Controlling the number of buckets]
-
-As more elements are added to an unordered associative container, the number
-of elements in the buckets will increase causing performance to degrade.
-To combat this the containers increase the bucket count as elements are inserted.
-You can also tell the container to change the bucket count (if required) by
-calling `rehash`.
-
-The standard leaves a lot of freedom to the implementer to decide how the
-number of buckets is chosen, but it does make some requirements based on the
-container's 'load factor', the average number of elements per bucket.
-Containers also have a 'maximum load factor' which they should try to keep the
-load factor below.
-
-You can't control the bucket count directly but there are two ways to
-influence it:
-
-* Specify the minimum number of buckets when constructing a container or
-  when calling `rehash`.
-* Suggest a maximum load factor by calling `max_load_factor`.
-
-`max_load_factor` doesn't let you set the maximum load factor yourself, it just
-lets you give a /hint/.  And even then, the draft standard doesn't actually
-require the container to pay much attention to this value. The only time the
-load factor is /required/ to be less than the maximum is following a call to
-`rehash`. But most implementations will try to keep the number of elements
-below the max load factor, and set the maximum load factor to be the same as
-or close to the hint - unless your hint is unreasonably small or large.
-
-[table:bucket_size Methods for Controlling Bucket Size
-    [[Method] [Description]]
-
-    [
-        [`X(size_type n)`]
-        [Construct an empty container with at least `n` buckets (`X` is the container type).]
-    ]
-    [
-        [`X(InputIterator i, InputIterator j, size_type n)`]
-        [Construct an empty container with at least `n` buckets and insert elements
-         from the range \[`i`, `j`) (`X` is the container type).]
-    ]
-    [
-        [`float load_factor() const`]
-        [The average number of elements per bucket.]
-    ]
-    [
-        [`float max_load_factor() const`]
-        [Returns the current maximum load factor.]
-    ]
-    [
-        [`float max_load_factor(float z)`]
-        [Changes the container's maximum load factor, using `z` as a hint.]
-    ]
-    [
-        [`void rehash(size_type n)`]
-        [Changes the number of buckets so that there at least `n` buckets, and
-        so that the load factor is less than the maximum load factor.]
-    ]
-
-]
-
-[h2 Iterator Invalidation]
-
-It is not specified how member functions other than `rehash` affect
-the bucket count, although `insert` is only allowed to invalidate iterators
-when the insertion causes the load factor to be greater than or equal to the
-maximum load factor. For most implementations this means that `insert` will only
-change the number of buckets when this happens. While iterators can be
-invalidated by calls to `insert` and `rehash`, pointers and references to the
-container's elements are never invalidated.
-
-In a similar manner to using `reserve` for `vector`s, it can be a good idea
-to call `rehash` before inserting a large number of elements. This will get
-the expensive rehashing out of the way and let you store iterators, safe in
-the knowledge that they won't be invalidated. If you are inserting `n`
-elements into container `x`, you could first call:
-
-    x.rehash((x.size() + n) / x.max_load_factor());
-
-[blurb Note: `rehash`'s argument is the minimum number of buckets, not the
-number of elements, which is why the new size is divided by the maximum load factor.]
-
-[endsect]

doc/comparison.qbk

@@ -1,161 +0,0 @@
-[/ Copyright 2006-2011 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[section:comparison Comparison with Associative Containers]
-
-[table:interface_differences Interface differences.
-    [[Associative Containers] [Unordered Associative Containers]]
-
-    [
-        [Parameterized by an ordering relation `Compare`]
-        [Parameterized by a function object `Hash` and an equivalence relation
-            `Pred`]
-    ]
-    [
-        [Keys can be compared using `key_compare` which is accessed by member function `key_comp()`,
-         values can be compared using `value_compare` which is accessed by member function `value_comp()`.]
-        [Keys can be hashed using `hasher` which is accessed by member function `hash_function()`,
-         and checked for equality using `key_equal` which is accessed by member function `key_eq()`.
-         There is no function object for compared or hashing values.]
-    ]
-    [
-        [Constructors have optional extra parameters for the comparison object.]
-        [Constructors have optional extra parameters for the initial minimum
-            number of buckets, a hash function and an equality object.]
-    ]
-
-    [
-        [Keys `k1`, `k2` are considered equivalent if
-            `!Compare(k1, k2) && !Compare(k2, k1)`]
-        [Keys `k1`, `k2` are considered equivalent if `Pred(k1, k2)`]
-    ]
-    [
-        [Member function `lower_bound(k)` and `upper_bound(k)`]
-        [No equivalent. Since the elements aren't ordered `lower_bound` and
-        `upper_bound` would be meaningless.]
-    ]
-    [
-        [`equal_range(k)` returns an empty range at the position that k
-            would be inserted if k isn't present in the container.]
-        [`equal_range(k)` returns a range at the end of the container if
-            k isn't present in the container. It can't return a positioned
-            range as k could be inserted into multiple place. To find out the
-            bucket that k would be inserted into use `bucket(k)`. But remember
-            that an insert can cause the container to rehash - meaning that the
-            element can be inserted into a different bucket.]
-    ]
-    [
-        [`iterator`, `const_iterator` are of the bidirectional category.]
-        [`iterator`, `const_iterator` are of at least the forward category.]
-    ]
-    [
-        [Iterators, pointers and references to the container's elements are
-            never invalidated.]
-        [[link unordered.buckets.iterator_invalidation Iterators can
-            be invalidated by calls to insert or rehash]. Pointers and
-            references to the container's elements are never invalidated.]
-    ]
-    [
-        [Iterators iterate through the container in the order defined by
-            the comparison object.]
-        [Iterators iterate through the container in an arbitrary order, that
-            can change as elements are inserted, although equivalent elements
-            are always adjacent.]
-    ]
-    [
-        [No equivalent]
-        [Local iterators can be used to iterate through individual buckets.
-            (The order of local iterators and iterators aren't
-            required to have any correspondence.)]
-    ]
-    [
-        [Can be compared using the `==`, `!=`, `<`, `<=`, `>`, `>=` operators.]
-        [Can be compared using the `==` and `!=` operators.]
-    ]
-    [
-        []
-        [When inserting with a hint, implementations are permitted to ignore
-            the hint.]
-    ]
-    [
-        [`erase` never throws an exception]
-        [The containers' hash or predicate function can throw exceptions
-            from `erase`]
-    ]
-]
-
-[table:complexity_guarantees Complexity Guarantees
-    [[Operation] [Associative Containers] [Unordered Associative Containers]]
-    [
-        [Construction of empty container]
-        [constant]
-        [O(/n/) where /n/ is the minimum number of buckets.]
-    ]
-    [
-        [Construction of container from a range of /N/ elements]
-        [O(/N/ log /N/), O(/N/) if the range is sorted with `value_comp()`]
-        [Average case O(/N/), worst case
-            O(/N/'''<superscript>2</superscript>''')]
-    ]
-    [
-        [Insert a single element]
-        [logarithmic]
-        [Average case constant, worst case linear]
-    ]
-    [
-        [Insert a single element with a hint]
-        [Amortized constant if t elements inserted right after hint,
-            logarithmic otherwise]
-        [Average case constant, worst case linear (ie. the same as
-            a normal insert).]
-    ]
-    [
-        [Inserting a range of /N/ elements]
-        [ /N/ log(`size()`+/N/) ]
-        [Average case O(/N/), worst case O(/N/ * `size()`)]
-    ]
-    [
-        [Erase by key, `k`]
-        [O(log(`size()`) + `count(k)`)]
-        [Average case: O(`count(k)`), Worst case: O(`size()`)]
-    ]
-    [
-        [Erase a single element by iterator]
-        [Amortized constant]
-        [Average case: O(1), Worst case: O(`size()`)]
-    ]
-    [
-        [Erase a range of /N/ elements]
-        [O(log(`size()`) + /N/)]
-        [Average case: O(/N/), Worst case: O(`size()`)]
-    ]
-    [
-        [Clearing the container]
-        [O(`size()`)]
-        [O(`size()`)]
-    ]
-    [
-        [Find]
-        [logarithmic]
-        [Average case: O(1), Worst case: O(`size()`)]
-    ]
-    [/ TODO: Average case is probably wrong. ]
-    [
-        [Count]
-        [O(log(`size()`) + `count(k)`)]
-        [Average case: O(1), Worst case: O(`size()`)]
-    ]
-    [
-        [`equal_range(k)`]
-        [logarithmic]
-        [Average case: O(`count(k)`), Worst case: O(`size()`)]
-    ]
-    [
-        [`lower_bound`,`upper_bound`]
-        [logarithmic]
-        [n/a]
-    ]
-]
-
-[endsect]

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doc/hash_equality.qbk

@@ -1,86 +0,0 @@
-[/ Copyright 2006-2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[section:hash_equality Equality Predicates and Hash Functions]
-
-While the associative containers use an ordering relation to specify how the
-elements are stored, the unordered associative containers use an equality
-predicate and a hash function. For example, [classref boost::unordered_map]
-is declared as:
-
-        template <
-            class Key, class Mapped,
-            class Hash = ``[classref boost::hash]``<Key>,
-            class Pred = std::equal_to<Key>,
-            class Alloc = std::allocator<std::pair<Key const, Mapped> > >
-        class ``[classref boost::unordered_map unordered_map]``;
-
-The hash function comes first as you might want to change the hash function
-but not the equality predicate. For example, if you wanted to use the
-[@http://www.isthe.com/chongo/tech/comp/fnv/ FNV-1 hash] you could write:
-
-[import src_code/dictionary.cpp]
-[case_sensitive_dictionary_fnv]
-
-There is an [@boost:/libs/unordered/examples/fnv1.hpp implementation
-of FNV-1] in the examples directory.
-
-If you wish to use a different equality function,
-you will also need to use a matching hash function. For
-example, to implement a case insensitive dictionary you need to define a
-case insensitive equality predicate and hash function:
-
-[case_insensitive_functions]
-
-Which you can then use in a case insensitive dictionary:
-
-[case_insensitive_dictionary]
-
-This is a simplified version of the example at
-[@boost:/libs/unordered/examples/case_insensitive.hpp /libs/unordered/examples/case_insensitive.hpp]
-which supports other locales and string types.
-
-[caution
-Be careful when using the equality (`==`) operator with custom equality
-predicates, especially if you're using a function pointer. If you compare two
-containers with different equality predicates then the result is undefined.
-For most stateless function objects this is impossible - since you can only
-compare objects with the same equality predicate you know the equality
-predicates must be equal. But if you're using function pointers or a stateful
-equality predicate (e.g. boost::function) then you can get into trouble.
-]
-
-[h2 Custom Types]
-
-Similarly, a custom hash function can be used for custom types:
-
-[import src_code/point1.cpp]
-[point_example1]
-
-Since the default hash function is [link hash Boost.Hash],
-we can [link hash.custom extend it to support the type]
-so that the hash function doesn't need to be explicitly given:
-
-[import src_code/point2.cpp]
-[point_example2]
-
-See the [link hash.custom Boost.Hash documentation] for more detail on how to
-do this.  Remember that it relies on extensions to the draft standard - so it
-won't work for other implementations of the unordered associative containers,
-you'll need to explicitly use Boost.Hash.
-
-[table:access_methods Methods for accessing the hash and equality functions.
-    [[Method] [Description]]
-
-    [
-        [`hasher hash_function() const`]
-        [Returns the container's hash function.]
-    ]
-    [
-        [`key_equal key_eq() const`]
-        [Returns the container's key equality function.]
-    ]
-]
-
-[endsect]

doc/intro.qbk

@@ -1,101 +0,0 @@
-[/ Copyright 2006-2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[def __hash-table__ [@http://en.wikipedia.org/wiki/Hash_table
-    hash table]]
-[def __hash-function__ [@http://en.wikipedia.org/wiki/Hash_function
-    hash function]]
-
-[section:intro Introduction]
-
-For accessing data based on key lookup, the C++ standard library offers `std::set`,
-`std::map`, `std::multiset` and `std::multimap`. These are generally
-implemented using balanced binary trees so that lookup time has
-logarithmic complexity. That is generally okay, but in many cases a
-__hash-table__ can perform better, as accessing data has constant complexity,
-on average. The worst case complexity is linear, but that occurs rarely and
-with some care, can be avoided.
-
-Also, the existing containers require a 'less than' comparison object
-to order their elements. For some data types this is impossible to implement
-or isn't practical. In contrast, a hash table only needs an equality function
-and a hash function for the key.
-
-With this in mind, unordered associative containers were added to the C++
-standard. This is an implementation of the containers described in C++11,
-with some [link unordered.compliance deviations from the standard] in
-order to work with non-C++11 compilers and libraries.
-
-`unordered_set` and `unordered_multiset` are defined in the header
-<[headerref boost/unordered_set.hpp]>
-
-    namespace boost {
-        template <
-            class Key,
-            class Hash = ``[classref boost::hash]``<Key>, 
-            class Pred = std::equal_to<Key>, 
-            class Alloc = std::allocator<Key> > 
-        class ``[classref boost::unordered_set unordered_set]``;
-
-        template<
-            class Key,
-            class Hash = ``[classref boost::hash]``<Key>, 
-            class Pred = std::equal_to<Key>, 
-            class Alloc = std::allocator<Key> > 
-        class ``[classref boost::unordered_multiset unordered_multiset]``;
-    }
-
-`unordered_map` and `unordered_multimap` are defined in the header
-<[headerref boost/unordered_map.hpp]>
-
-    namespace boost {
-        template <
-            class Key, class Mapped,
-            class Hash = ``[classref boost::hash]``<Key>,
-            class Pred = std::equal_to<Key>,
-            class Alloc = std::allocator<std::pair<Key const, Mapped> > >
-        class ``[classref boost::unordered_map unordered_map]``;
-
-        template<
-            class Key, class Mapped,
-            class Hash = ``[classref boost::hash]``<Key>,
-            class Pred = std::equal_to<Key>,
-            class Alloc = std::allocator<std::pair<Key const, Mapped> > >
-        class ``[classref boost::unordered_multimap unordered_multimap]``;
-    }
-
-When using Boost.TR1, these classes are included from `<unordered_set>` and
-`<unordered_map>`, with the classes added to the `std::tr1` namespace.
-
-The containers are used in a similar manner to the normal associative
-containers:
-
-[import src_code/intro.cpp]
-[intro_example1_2]
-
-But since the elements aren't ordered, the output of:
-
-[intro_example1_3]
-
-can be in any order. For example, it might be:
-
-    two,2
-    one,1
-    three,3
-
-To store an object in an unordered associative container requires both a
-key equality function and a hash function. The default function objects in
-the standard containers support a few basic types including integer types,
-floating point types, pointer types, and the standard strings. Since
-Boost.Unordered uses [classref boost::hash] it also supports some other types,
-including standard containers. To use any types not supported by these methods
-you have to [link hash.custom extend Boost.Hash to support the type] or use
-your own custom equality predicates and hash functions. See the
-[link unordered.hash_equality Equality Predicates and Hash Functions] section
-for more details.
-
-There are other differences, which are listed in the
-[link unordered.comparison Comparison with Associative Containers] section.
-
-[endsect]

doc/preview.md

@@ -0,0 +1,47 @@
+# Building Boost from the Tip of Develop
+
+To build Boost from the tip of the develop branch without cloning the entire 
+history, use the command below:
+
+Linux:
+```bash
+cwd=$(pwd) \
+  && cd ~ \
+  && git clone -b develop --depth 1 --recurse-submodules --shallow-submodules --jobs 8 https://github.com/boostorg/boost.git boost-develop-beta \
+  && cd boost-develop-beta \
+  && ./bootstrap.sh \
+  && ./b2 install --prefix=boost-install cxxstd=17 \
+  && echo "Boost successfully installed into $(realpath boost-install)!
+  Add this to your CMake toolchain file.
+  list(APPEND CMAKE_PREFIX_PATH $(realpath boost-install))
+  " \
+  && cd $cwd
+```
+
+Windows (using plain Command Prompt):
+```bat
+cmd /v
+set cwd=%cd% ^
+  && cd %homepath% ^
+  && git clone -b develop --depth 1 --recurse-submodules --shallow-submodules --jobs 8 https://github.com/boostorg/boost.git boost-develop-beta ^
+  && cd boost-develop-beta ^
+  && bootstrap.bat ^
+  && b2 install --prefix=boost-install cxxstd=17 address-model=64 ^
+  && echo Boost successfully installed into !cd!\boost-install! ^
+  && echo Add this to your CMake toolchain file. ^
+  && echo list(APPEND CMAKE_PREFIX_PATH !cd:\=/!/boost-install) ^
+  && cd !cwd! ^
+  && exit
+```
+
+Note: you can build Boost with a specific compiler by setting the toolset in 
+the `./b2` command above. To build with clang, specify `toolset=clang`; to build
+with a specific version of gcc, clang or msvc, specify e.g. `toolset=gcc-12` for GCC 
+12, `clang-14` for Clang 14, `msvc-14.3` for MSVC 14.3. The value of `cxxstd` 
+can also be set to other values such as 11 for C++11, 14 for C++14, etc.
+
+For more info on what's possible, check out this link on b2:
+https://www.boost.org/doc/libs/develop/tools/build/doc/html/index.html#bbv2.overview.builtins.features
+
+This should hopefully cover the two most common cases of building a dependency, 
+setting the compiler and C++ standard used.

doc/rationale.qbk

@@ -1,111 +0,0 @@
-[/ Copyright 2006-2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[def __wang__
-    [@http://web.archive.org/web/20121102023700/http://www.concentric.net/~Ttwang/tech/inthash.htm
-    Thomas Wang's article on integer hash functions]]
-
-[section:rationale Implementation Rationale]
-
-The intent of this library is to implement the unordered
-containers in the draft standard, so the interface was fixed. But there are
-still some implementation decisions to make. The priorities are
-conformance to the standard and portability.
-
-The [@http://en.wikipedia.org/wiki/Hash_table Wikipedia article on hash tables]
-has a good summary of the implementation issues for hash tables in general.
-
-[h2 Data Structure]
-
-By specifying an interface for accessing the buckets of the container the
-standard pretty much requires that the hash table uses chained addressing.
-
-It would be conceivable to write a hash table that uses another method.  For
-example, it could use open addressing, and use the lookup chain to act as a
-bucket but there are some serious problems with this:
-
-* The draft standard requires that pointers to elements aren't invalidated, so
-  the elements can't be stored in one array, but will need a layer of
-  indirection instead - losing the efficiency and most of the memory gain,
-  the main advantages of open addressing.
-
-* Local iterators would be very inefficient and may not be able to
-  meet the complexity requirements.
-  
-* There are also the restrictions on when iterators can be invalidated. Since
-  open addressing degrades badly when there are a high number of collisions the
-  restrictions could prevent a rehash when it's really needed. The maximum load
-  factor could be set to a fairly low value to work around this - but the
-  standard requires that it is initially set to 1.0.
-
-* And since the standard is written with a eye towards chained
-  addressing, users will be surprised if the performance doesn't reflect that.
-
-So chained addressing is used.
-
-[/ (Removing for now as this is out of date)
-
-For containers with unique keys I store the buckets in a single-linked list.
-There are other possible data structures (such as a double-linked list)
-that allow for some operations to be faster (such as erasing and iteration)
-but the possible gain seems small compared to the extra memory needed.
-The most commonly used operations (insertion and lookup) would not be improved
-at all.
-
-But for containers with equivalent keys a single-linked list can degrade badly
-when a large number of elements with equivalent keys are inserted. I think it's
-reasonable to assume that users who choose to use `unordered_multiset` or
-`unordered_multimap` do so because they are likely to insert elements with
-equivalent keys. So I have used an alternative data structure that doesn't
-degrade, at the expense of an extra pointer per node.
-
-This works by adding storing a circular linked list for each group of equivalent
-nodes in reverse order. This allows quick navigation to the end of a group (since
-the first element points to the last) and can be quickly updated when elements
-are inserted or erased. The main disadvantage of this approach is some hairy code
-for erasing elements.
-]
-
-[/ (Starting to write up new structure, might not be ready in time)
-The node used to be stored in a linked list for each bucket but that
-didn't meet the complexity requirements for C++11, so now the nodes
-are stored in one long single linked list. But there needs a way to get
-the bucket from the node, to do that a copy of the key's hash value is
-stored in the node. Another possibility would be to store a pointer to
-the bucket, or the bucket's index, but storing the hash value allows
-some operations to be faster.
-]
-
-[h2 Number of Buckets]
-
-There are two popular methods for choosing the number of buckets in a hash
-table. One is to have a prime number of buckets, another is to use a power
-of 2.
-
-Using a prime number of buckets, and choosing a bucket by using the modulus
-of the hash function's result will usually give a good result. The downside
-is that the required modulus operation is fairly expensive. This is what the
-containers do in most cases.
-
-Using a power of 2 allows for much quicker selection of the bucket
-to use, but at the expense of losing the upper bits of the hash value.
-For some specially designed hash functions it is possible to do this and
-still get a good result but as the containers can take arbitrary hash
-functions this can't be relied on.
-
-To avoid this a transformation could be applied to the hash function, for an
-example see __wang__.  Unfortunately, a transformation like Wang's requires
-knowledge of the number of bits in the hash value, so it isn't portable enough
-to use as a default. It can applicable in certain cases so the containers
-have a policy based implementation that can use this alternative technique.
-
-Currently this is only done on 64 bit architectures, where prime number
-modulus can be expensive. Although this varies depending on the architecture,
-so I probably should revisit it.
-
-I'm also thinking of introducing a mechanism whereby a hash function can
-indicate that it's safe to be used directly with power of 2 buckets, in
-which case a faster plain power of 2 implementation can be used.
-
-[endsect]

doc/roadmap.md

@@ -0,0 +1,188 @@
+# Refactoring Roadmap
+
+[Proof of concept](https://github.com/joaquintides/fca_unordered) implementation for a fast closed-addressing implementation.
+
+## Plan of Refactoring
+
+* remove `ptr_node` and `ptr_bucket`
+* see if the code can survive a lack of the `extra_node` or maybe we hard-code it in
+* implement bucket groups as they are in `fca` but don't use them directly yet, add alongside the `buckets_` data member in `struct table`
+* try to remove `bucket_info_` from the node structure (breaks all call-sites that use `get_bucket()` and dependents)
+* make sure `fca` can successfully handle multi-variants at this stage + supports mutable iterators for `map`/`multimap`
+* do a hard-break:
+    * update code to no longer use one single linked list across all buckets (each bucket contains its own unique list)
+    * integrate the `bucket_group<Node>` structure into the `table` (update iterator call-sites to include `bucket_iterator`s)
+
+Blockers:
+* how to handle `multi` variants with new `fca` prototype
+
+## Implementation Differences
+
+### Unordered
+
+### Node Type
+
+Bullet Points:
+* reify node type into a single one
+* come up with implementation for multi- variants
+* code that touches `get_bucket()` and `*_in_group()` member functions may need updating
+
+There are two node types in Unordered, `struct node` and `struct ptr_node`, and the node type is selected conditionally based on the Allocator's pointer type:
+```c++
+template <typename A, typename T, typename NodePtr, typename BucketPtr>
+struct pick_node2
+{
+  typedef boost::unordered::detail::node<A, T> node;
+  // ...
+};
+
+template <typename A, typename T>
+struct pick_node2<A, T, boost::unordered::detail::ptr_node<T>*,
+  boost::unordered::detail::ptr_bucket*>
+{ 
+  typedef boost::unordered::detail::ptr_node<T> node;
+  // ...
+};
+
+template <typename A, typename T> struct pick_node
+{
+  typedef typename boost::remove_const<T>::type nonconst;
+
+  typedef boost::unordered::detail::allocator_traits<
+    typename boost::unordered::detail::rebind_wrap<A,
+      boost::unordered::detail::ptr_node<nonconst> >::type>
+    tentative_node_traits;
+
+  typedef boost::unordered::detail::allocator_traits<
+    typename boost::unordered::detail::rebind_wrap<A,
+      boost::unordered::detail::ptr_bucket>::type>
+    tentative_bucket_traits;
+
+  typedef pick_node2<A, nonconst, typename tentative_node_traits::pointer,
+    typename tentative_bucket_traits::pointer>
+    pick;
+
+  typedef typename pick::node node;
+  typedef typename pick::bucket bucket;
+  typedef typename pick::link_pointer link_pointer;
+};
+```
+
+The node types are identical in terms of interface and the only difference is that `node` is chosen when the Allocator uses fancy pointers and `ptr_node` is chosen when the Allocator's pointer type is `T*`.
+
+Nodes in Unorderd store `bucket_info_`:
+```cpp
+template <typename A, typename T>
+struct node : boost::unordered::detail::value_base<T>
+{
+  link_pointer next_;
+  std::size_t bucket_info_;
+  node() : next_(), bucket_info_(0) {}
+  // ...
+};
+```
+
+`bucket_info_` maps each node back to its corresponding bucket via the member function:
+```cpp
+std::size_t get_bucket() const
+{
+  return bucket_info_ & ((std::size_t)-1 >> 1);
+}
+```
+
+`bucket_info_` is also used to demarcate the start of equivalent nodes in the containers via:
+```cpp
+// Note that nodes start out as the first in their group, as `bucket_info_` defaults to 0.
+std::size_t is_first_in_group() const
+{ return !(bucket_info_ & ~((std::size_t)-1 >> 1)); }
+
+void set_first_in_group()
+{ bucket_info_ = bucket_info_ & ((std::size_t)-1 >> 1); }
+
+void reset_first_in_group()
+{ bucket_info_ = bucket_info_ | ~((std::size_t)-1 >> 1); }
+```
+
+A goal of refactoring is to simply have one node type:
+```cpp
+template<class T>
+struct node {
+  node *next;
+  T    value;
+};
+```
+that is used unconditionally. This also requires updating the code that touches the `bucket_info_` along with the code that that touches the `*_in_group()` member functions.
+
+### Bucket Type
+
+Bullet points:
+* reify bucket structure into a single one
+* figure out how to add `bucket_group`s to the table struct
+
+Buckets are similar to nodes in that there are two variations: `template<class NodePointer> struct bucket` and `struct ptr_bucket`.
+
+The buckets exist to contain a pointer to a node, however they contain an `enum { extra_node = true };` or `enum { extra_node = false }` to determine whether or not the code should explicitly allocate a default constructed node whose address assigned as the dummy node at the end of the bucket array.
+
+`extra_node` is used in the creation and deletion of the bucket array but it is not inherently clear what its intended purpose is.
+
+### Iterators
+
+Iterators are currently templated on the type of Node they store. Because `fca` constructs iterators with two arguments, all the call-sites that instantiate iterators will need to be updated but this a straight-forward mechanical change.
+
+Iterators are selected, as of now, via the `detail::map` and `detail::set` class templates.
+
+For example, for `unordered_map`, `iterator` is defined as:
+```cpp
+typedef boost::unordered::detail::map<A, K, T, H, P> types;
+typedef typename types::table table;
+typedef typename table::iterator iterator;
+```
+
+The iterator is a member typedef of the `table` which is `types::table`. Examining `types` (aka `detail::map<...>`), we see:
+```cpp
+template <typename A, typename K, typename M, typename H, typename P>
+struct map {
+  // ...
+  typedef boost::unordered::detail::table<types> table;
+  // ...
+};
+```
+
+Examining the `detail::table<types>` struct, we see:
+```cpp
+template <typename Types>
+struct table {
+  // ...
+  typedef typename Types::iterator iterator;
+  // ...
+}
+```
+
+Collapsing all of this, we see that our iterator types are defined here:
+```cpp
+template <typename A, typename K, typename M, typename H, typename P>
+struct map
+{
+  // ...
+  typedef boost::unordered::detail::pick_node<A, value_type> pick;
+  typedef typename pick::node node;
+
+  typedef boost::unordered::iterator_detail::iterator<node> iterator;
+  typedef boost::unordered::iterator_detail::c_iterator<node> c_iterator;
+  typedef boost::unordered::iterator_detail::l_iterator<node> l_iterator;
+  typedef boost::unordered::iterator_detail::cl_iterator<node>
+    cl_iterator;
+  // ...
+};
+```
+
+This is similarly designed for `detail::set`:
+```cpp
+typedef boost::unordered::iterator_detail::c_iterator<node> iterator;
+typedef boost::unordered::iterator_detail::c_iterator<node> c_iterator;
+typedef boost::unordered::iterator_detail::cl_iterator<node> l_iterator;
+typedef boost::unordered::iterator_detail::cl_iterator<node>
+  cl_iterator;
+```
+
+The only difference here is that `set::iterator` is always a `c_iterator`, a `const_iterator` type.

doc/src_code/dictionary.cpp

@@ -1,101 +0,0 @@
-
-// Copyright 2006-2007 Daniel James.
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-#include <boost/unordered_map.hpp>
-#include <boost/core/lightweight_test.hpp>
-#include <boost/algorithm/string/predicate.hpp>
-#include "../../examples/fnv1.hpp"
-
-//[case_insensitive_functions
-    struct iequal_to
-    {
-        bool operator()(std::string const& x,
-            std::string const& y) const
-        {
-            return boost::algorithm::iequals(x, y, std::locale());
-        }
-    };
-
-    struct ihash
-    {
-        std::size_t operator()(std::string const& x) const
-        {
-            std::size_t seed = 0;
-            std::locale locale;
-
-            for(std::string::const_iterator it = x.begin();
-                it != x.end(); ++it)
-            {
-                boost::hash_combine(seed, std::toupper(*it, locale));
-            }
-
-            return seed;
-        }
-    };
-//]
-
-int main() {
-//[case_sensitive_dictionary_fnv
-    boost::unordered_map<std::string, int, hash::fnv_1>
-        dictionary;
-//]
-
-    BOOST_TEST(dictionary.empty());
-
-    dictionary["one"] = 1;
-    BOOST_TEST(dictionary.size() == 1);
-    BOOST_TEST(dictionary.find("ONE") == dictionary.end());
-
-    dictionary.insert(std::make_pair("ONE", 2));
-    BOOST_TEST(dictionary.size() == 2);
-    BOOST_TEST(dictionary.find("ONE") != dictionary.end() &&
-            dictionary.find("ONE")->first == "ONE" &&
-            dictionary.find("ONE")->second == 2);
-
-    dictionary["One"] = 3;
-    BOOST_TEST(dictionary.size() == 3);
-    BOOST_TEST(dictionary.find("One") != dictionary.end() &&
-            dictionary.find("One")->first == "One" &&
-            dictionary.find("One")->second == 3);
-
-    dictionary["two"] = 4;
-    BOOST_TEST(dictionary.size() == 4);
-    BOOST_TEST(dictionary.find("Two") == dictionary.end() &&
-            dictionary.find("two") != dictionary.end() &&
-            dictionary.find("two")->second == 4);
-
-
-//[case_insensitive_dictionary
-    boost::unordered_map<std::string, int, ihash, iequal_to>
-        idictionary;
-//]
-
-    BOOST_TEST(idictionary.empty());
-
-    idictionary["one"] = 1;
-    BOOST_TEST(idictionary.size() == 1);
-    BOOST_TEST(idictionary.find("ONE") != idictionary.end() &&
-        idictionary.find("ONE") == idictionary.find("one"));
-
-    idictionary.insert(std::make_pair("ONE", 2));
-    BOOST_TEST(idictionary.size() == 1);
-    BOOST_TEST(idictionary.find("ONE") != idictionary.end() &&
-            idictionary.find("ONE")->first == "one" &&
-            idictionary.find("ONE")->second == 1);
-
-    idictionary["One"] = 3;
-    BOOST_TEST(idictionary.size() == 1);
-    BOOST_TEST(idictionary.find("ONE") != idictionary.end() &&
-            idictionary.find("ONE")->first == "one" &&
-            idictionary.find("ONE")->second == 3);
-
-    idictionary["two"] = 4;
-    BOOST_TEST(idictionary.size() == 2);
-    BOOST_TEST(idictionary.find("two") != idictionary.end() &&
-            idictionary.find("TWO")->first == "two" &&
-            idictionary.find("Two")->second == 4);
-
-    return boost::report_errors();
-}

doc/src_code/intro.cpp

@@ -1,30 +0,0 @@
-
-// Copyright 2006-2009 Daniel James.
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-//[intro_example1_1
-#include <boost/unordered_map.hpp>
-#include <boost/foreach.hpp>
-#include <cassert>
-#include <iostream>
-//]
-
-int main() {
-//[intro_example1_2
-    typedef boost::unordered_map<std::string, int> map;
-    map x;
-    x["one"] = 1;
-    x["two"] = 2;
-    x["three"] = 3;
-
-    assert(x.at("one") == 1);
-    assert(x.find("missing") == x.end());
-//]
-
-//[intro_example1_3
-    BOOST_FOREACH(map::value_type i, x) {
-        std::cout<<i.first<<","<<i.second<<"\n";
-    }
-//]
-}

doc/src_code/point1.cpp

@@ -1,44 +0,0 @@
-
-// Copyright 2006-2009 Daniel James.
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-#include <boost/unordered_set.hpp>
-#include <boost/core/lightweight_test.hpp>
-
-//[point_example1
-    struct point {
-        int x;
-        int y;
-    };
-
-    bool operator==(point const& p1, point const& p2)
-    {
-        return p1.x == p2.x && p1.y == p2.y;
-    }
-
-    struct point_hash
-    {
-        std::size_t operator()(point const& p) const
-        {
-            std::size_t seed = 0;
-            boost::hash_combine(seed, p.x);
-            boost::hash_combine(seed, p.y);
-            return seed;
-        }
-    };
-
-    boost::unordered_multiset<point, point_hash> points;
-//]
-
-int main() {
-    point x[] = {{1,2}, {3,4}, {1,5}, {1,2}};
-    for(int i = 0; i < sizeof(x) / sizeof(point); ++i)
-        points.insert(x[i]);
-    BOOST_TEST(points.count(x[0]) == 2);
-    BOOST_TEST(points.count(x[1]) == 1);
-    point y = {10, 2};
-    BOOST_TEST(points.count(y) == 0);
-
-    return boost::report_errors();
-}

doc/src_code/point2.cpp

@@ -1,43 +0,0 @@
-
-// Copyright 2006-2009 Daniel James.
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-#include <boost/unordered_set.hpp>
-#include <boost/functional/hash.hpp>
-#include <boost/core/lightweight_test.hpp>
-
-//[point_example2
-    struct point {
-        int x;
-        int y;
-    };
-
-    bool operator==(point const& p1, point const& p2)
-    {
-        return p1.x == p2.x && p1.y == p2.y;
-    }
-
-    std::size_t hash_value(point const& p) {
-        std::size_t seed = 0;
-        boost::hash_combine(seed, p.x);
-        boost::hash_combine(seed, p.y);
-        return seed;
-    }
-
-    // Now the default function objects work.
-    boost::unordered_multiset<point> points;
-//]
-
-int main() {
-    point x[] = {{1,2}, {3,4}, {1,5}, {1,2}};
-    for(int i = 0; i < sizeof(x) / sizeof(point); ++i)
-        points.insert(x[i]);
-    BOOST_TEST(points.count(x[0]) == 2);
-    BOOST_TEST(points.count(x[1]) == 1);
-    point y = {10, 2};
-    BOOST_TEST(points.count(y) == 0);
-
-    return boost::report_errors();
-}
-

doc/unordered.adoc

@@ -0,0 +1,23 @@
+= Boost.Unordered
+:toc: left
+:toclevels: 3
+:idprefix:
+:docinfo: private-footer
+:source-highlighter: rouge
+:source-language: c++
+:nofooter:
+:sectlinks:
+
+:leveloffset: +1
+
+include::unordered/intro.adoc[]
+include::unordered/buckets.adoc[]
+include::unordered/benchmarks.adoc[]
+include::unordered/hash_equality.adoc[]
+include::unordered/comparison.adoc[]
+include::unordered/compliance.adoc[]
+include::unordered/rationale.adoc[]
+include::unordered/ref.adoc[]
+include::unordered/changes.adoc[]
+include::unordered/bibliography.adoc[]
+include::unordered/copyright.adoc[]

doc/unordered.qbk

@@ -1,39 +0,0 @@
-[/ Copyright 2006-2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
-
-[library Boost.Unordered
-    [quickbook 1.7]
-    [compatibility-mode 1.5]
-    [authors [James, Daniel]]
-    [copyright 2003 2004 Jeremy B. Maitin-Shepard]
-    [copyright 2005 2006 2007 2008 Daniel James]
-    [purpose std::tr1 compliant hash containers]
-    [id unordered]
-    [dirname unordered]
-    [license
-        Distributed under the Boost Software License, Version 1.0.
-        (See accompanying file LICENSE_1_0.txt or copy at
-        [@http://www.boost.org/LICENSE_1_0.txt])
-    ]
-]
-
-[template diagram[name]  '''<inlinemediaobject>
-<imageobject role="html">
-<imagedata align = "center" fileref="../../libs/unordered/doc/diagrams/'''[name]'''.png"></imagedata>
-</imageobject>
-<imageobject role="print">
-<imagedata align = "center" fileref="../../libs/unordered/doc/diagrams/'''[name]'''.svg"></imagedata>
-</imageobject>
-</inlinemediaobject>''']
-
-
-[include:unordered intro.qbk]
-[include:unordered buckets.qbk]
-[include:unordered hash_equality.qbk]
-[include:unordered comparison.qbk]
-[include:unordered compliance.qbk]
-[include:unordered rationale.qbk]
-[include:unordered changes.qbk]
-[xinclude ref.xml]
-[xinclude bibliography.xml]

doc/unordered/benchmarks.adoc

@@ -0,0 +1,277 @@
+[#benchmarks]
+:idprefix: benchmarks_
+:imagesdir: ../diagrams
+
+= Benchmarks
+
+All benchmarks were created using `unordered_set<unsigned int>` (non-duplicate) and `unordered_multiset<unsigned int>` (duplicate). The source code can be https://github.com/joaquintides/boost_unordered_benchmark[found here].
+
+The insertion benchmarks insert `n` random values, where `n` is between 10,000 and 3 million. For the duplicated benchmarks, the same random values are repeated an average of 5 times.
+
+The erasure benchmarks erase all `n` elements randomly until the container is empty.
+
+The successful lookup benchmarks are done by looking up all `n` values, in the their original insertion order.
+
+The unsuccessful lookup benchmarks use `n` randomly generated integers but using a different seed value.
+
+== GCC 11 + libstdc++-v3
+
+=== Insertion
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/gcc/running insertion.xlsx.practice.png[width=250,link=../diagrams/benchmarks/gcc/running insertion.xlsx.practice.png,window=_blank]
+|image::benchmarks/gcc/running%20insertion.xlsx.practice non-unique.png[width=250,link=../diagrams/benchmarks/gcc/running%20insertion.xlsx.practice non-unique.png,window=_blank]
+|image::benchmarks/gcc/running%20insertion.xlsx.practice non-unique 5.png[width=250,link=../diagrams/benchmarks/gcc/running%20insertion.xlsx.practice non-unique 5.png,window=_blank]
+
+h|non-duplicate elements 
+h|duplicate elements 
+h|duplicate elements +
+max load factor 5
+|===
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/gcc/running%20insertion.xlsx.practice norehash.png[width=250,link=../diagrams/benchmarks/gcc/running%20insertion.xlsx.practice norehash.png,window=_blank]
+|image::benchmarks/gcc/running%20insertion.xlsx.practice norehash non-unique.png[width=250,link=../diagrams/benchmarks/gcc/running%20insertion.xlsx.practice norehash non-unique.png,window=_blank]
+|image::benchmarks/gcc/running%20insertion.xlsx.practice norehash non-unique 5.png[width=250,link=../diagrams/benchmarks/gcc/running%20insertion.xlsx.practice norehash non-unique 5.png,window=_blank]
+
+h|non-duplicate elements, +
+prior `reserve`
+h|duplicate elements, +
+prior `reserve` 
+h|duplicate elements, +
+max load factor 5, +
+prior `reserve`
+
+|===
+
+=== Erasure
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/gcc/scattered%20erasure.xlsx.practice.png[width=250,link=../diagrams/benchmarks/gcc/scattered%20erasure.xlsx.practice.png,window=_blank]
+|image::benchmarks/gcc/scattered%20erasure.xlsx.practice non-unique.png[width=250,link=../diagrams/benchmarks/gcc/scattered%20erasure.xlsx.practice non-unique.png,window=_blank]
+|image::benchmarks/gcc/scattered%20erasure.xlsx.practice non-unique 5.png[width=250,link=../diagrams/benchmarks/gcc/scattered%20erasure.xlsx.practice non-unique 5.png,window=_blank]
+
+h|non-duplicate elements 
+h|duplicate elements 
+h|duplicate elements +
+max load factor 5
+|===
+
+=== Successful Lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice.png]
+|image::benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20successful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+=== Unsuccessful lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice.png]
+|image::benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/gcc/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+== Clang 12 + libc++
+
+=== Insertion
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice.png[width=250, window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice.png]
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice non-unique.png[width=250, window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice non-unique.png]
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice non-unique 5.png[width=250, window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash.png]
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash non-unique.png]
+|image::benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/running%20insertion.xlsx.practice norehash non-unique 5.png]
+
+h|non-duplicate elements, +
+prior `reserve`
+h|duplicate elements, +
+prior `reserve`
+h|duplicate elements, +
+max load factor 5, +
+prior `reserve`
+
+|===
+
+=== Erasure
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice.png]
+|image::benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice non-unique.png]
+|image::benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20erasure.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+=== Successful lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice.png]
+|image::benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20successful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+=== Unsuccessful lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice.png]
+|image::benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/clang_libcpp/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+== Visual Studio 2019 + Dinkumware
+
+=== Insertion
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/vs/running%20insertion.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice.png]
+|image::benchmarks/vs/running%20insertion.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice non-unique.png]
+|image::benchmarks/vs/running%20insertion.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/vs/running%20insertion.xlsx.practice norehash.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice norehash.png]
+|image::benchmarks/vs/running%20insertion.xlsx.practice norehash non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice norehash non-unique.png]
+|image::benchmarks/vs/running%20insertion.xlsx.practice norehash non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/running%20insertion.xlsx.practice norehash non-unique 5.png]
+
+h|non-duplicate elements, +
+prior `reserve`
+h|duplicate elements, +
+prior `reserve`
+h|duplicate elements, +
+max load factor 5, +
+prior `reserve`
+
+|===
+
+=== Erasure
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/vs/scattered%20erasure.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20erasure.xlsx.practice.png]
+|image::benchmarks/vs/scattered%20erasure.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20erasure.xlsx.practice non-unique.png]
+|image::benchmarks/vs/scattered%20erasure.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20erasure.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+=== Successful lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/vs/scattered%20successful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20successful%20looukp.xlsx.practice.png]
+|image::benchmarks/vs/scattered%20successful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20successful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/vs/scattered%20successful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20successful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===
+
+=== Unsuccessful lookup
+
+[caption=]
+[cols="3*^.^a", frame=all, grid=all]
+|===
+
+|image::benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice.png]
+|image::benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice non-unique.png]
+|image::benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png[width=250,window=_blank,link=../diagrams/benchmarks/vs/scattered%20unsuccessful%20looukp.xlsx.practice non-unique 5.png]
+
+h|non-duplicate elements
+h|duplicate elements
+h|duplicate elements, +
+max load factor 5
+
+|===

doc/unordered/bibliography.adoc

@@ -0,0 +1,10 @@
+[#bibliography]
+
+:idprefix: bibliography_
+
+= Bibliography
+
+* _C/C++ Users Journal_. February, 2006. Pete Becker. http://www.ddj.com/cpp/184402066[STL and TR1: Part III - Unordered containers^]. +
+An introducation to the standard unordered containers.
+
+

doc/unordered/buckets.adoc

@@ -0,0 +1,210 @@
+[#buckets]
+:idprefix: buckets_
+:imagesdir: ../diagrams
+
+= The Data Structure
+
+The containers are made up of a number of 'buckets', each of which can contain
+any number of elements. For example, the following diagram shows an <<unordered_set,unordered_set>> with 7 buckets containing 5 elements, `A`,
+`B`, `C`, `D` and `E` (this is just for illustration, containers will typically
+have more buckets).
+
+image::buckets.png[]
+
+In order to decide which bucket to place an element in, the container applies
+the hash function, `Hash`, to the element's key (for `unordered_set` and
+`unordered_multiset` the key is the whole element, but is referred to as the key
+so that the same terminology can be used for sets and maps). This returns a
+value of type `std::size_t`. `std::size_t` has a much greater range of values
+then the number of buckets, so the container applies another transformation to
+that value to choose a bucket to place the element in.
+
+Retrieving the elements for a given key is simple. The same process is applied
+to the key to find the correct bucket. Then the key is compared with the
+elements in the bucket to find any elements that match (using the equality
+predicate `Pred`). If the hash function has worked well the elements will be
+evenly distributed amongst the buckets so only a small number of elements will
+need to be examined.
+
+There is <<hash_equality, more information on hash functions and
+equality predicates in the next section>>.
+
+You can see in the diagram that `A` & `D` have been placed in the same bucket.
+When looking for elements in this bucket up to 2 comparisons are made, making
+the search slower. This is known as a collision. To keep things fast we try to
+keep collisions to a minimum.
+
+[caption=, title='Table {counter:table-counter}. Methods for Accessing Buckets']
+[cols="1,.^1", frame=all, grid=rows]
+|===
+|Method |Description
+
+|`size_type bucket_count() const` 
+|The number of buckets.
+
+|`size_type max_bucket_count() const` 
+|An upper bound on the number of buckets.
+
+|`size_type bucket_size(size_type n) const` 
+|The number of elements in bucket `n`.
+
+|`size_type bucket(key_type const& k) const`
+|Returns the index of the bucket which would contain `k`.
+
+|`local_iterator begin(size_type n)`
+1.6+|Return begin and end iterators for bucket `n`.
+
+|`local_iterator end(size_type n)`
+
+|`const_local_iterator begin(size_type n) const`
+
+|`const_local_iterator end(size_type n) const`
+
+|`const_local_iterator cbegin(size_type n) const`
+
+|`const_local_iterator cend(size_type n) const`
+
+|===
+
+== Controlling the number of buckets
+
+As more elements are added to an unordered associative container, the number
+of elements in the buckets will increase causing performance to degrade.
+To combat this the containers increase the bucket count as elements are inserted.
+You can also tell the container to change the bucket count (if required) by
+calling `rehash`.
+
+The standard leaves a lot of freedom to the implementer to decide how the
+number of buckets is chosen, but it does make some requirements based on the
+container's 'load factor', the average number of elements per bucket.
+Containers also have a 'maximum load factor' which they should try to keep the
+load factor below.
+
+You can't control the bucket count directly but there are two ways to
+influence it:
+
+* Specify the minimum number of buckets when constructing a container or when calling `rehash`.
+* Suggest a maximum load factor by calling `max_load_factor`.
+
+`max_load_factor` doesn't let you set the maximum load factor yourself, it just
+lets you give a _hint_. And even then, the standard doesn't actually
+require the container to pay much attention to this value. The only time the
+load factor is _required_ to be less than the maximum is following a call to
+`rehash`. But most implementations will try to keep the number of elements
+below the max load factor, and set the maximum load factor to be the same as
+or close to the hint - unless your hint is unreasonably small or large.
+
+[caption=, title='Table {counter:table-counter}. Methods for Controlling Bucket Size']
+[cols="1,.^1", frame=all, grid=rows]
+|===
+|Method |Description
+
+|`X(size_type n)` 
+|Construct an empty container with at least `n` buckets (`X` is the container type).
+
+|`X(InputIterator i, InputIterator j, size_type n)` 
+|Construct an empty container with at least `n` buckets and insert elements from the range `[i, j)` (`X` is the container type).
+
+|`float load_factor() const` 
+|The average number of elements per bucket.
+
+|`float max_load_factor() const`
+|Returns the current maximum load factor.
+
+|`float max_load_factor(float z)`
+|Changes the container's maximum load factor, using `z` as a hint.
+
+|`void rehash(size_type n)`
+|Changes the number of buckets so that there at least `n` buckets, and so that the load factor is less than the maximum load factor.
+
+|===
+
+== Iterator Invalidation
+
+It is not specified how member functions other than `rehash` and `reserve` affect
+the bucket count, although `insert` is only allowed to invalidate iterators
+when the insertion causes the load factor to be greater than or equal to the
+maximum load factor. For most implementations this means that `insert` will only
+change the number of buckets when this happens. While iterators can be
+invalidated by calls to `insert`, `rehash` and `reserve`, pointers and references to the
+container's elements are never invalidated.
+
+In a similar manner to using `reserve` for ``vector``s, it can be a good idea
+to call `reserve` before inserting a large number of elements. This will get
+the expensive rehashing out of the way and let you store iterators, safe in
+the knowledge that they won't be invalidated. If you are inserting `n`
+elements into container `x`, you could first call:
+
+```
+x.reserve(n);
+```
+
+Note:: `reserve(n)` reserves space for at least `n` elements, allocating enough buckets
+so as to not exceed the maximum load factor.
++
+Because the maximum load factor is defined as the number of elements divided by the total
+number of available buckets, this function is logically equivalent to:
++
+```
+x.rehash(std::ceil(n / x.max_load_factor()))
+```
++
+See the <<unordered_map_rehash,reference for more details>> on the `rehash` function.
+
+== Fast Closed Addressing Implementation
+
+++++
+<style>
+  .imageblock > .title {
+    text-align: inherit;
+  }
+</style>
+++++
+
+Boost.Unordered sports one of the fastest implementations of closed addressing, also commonly known as https://en.wikipedia.org/wiki/Hash_table#Separate_chaining[separate chaining]. An example figure representing the data structure is below:
+
+[#img-bucket-groups,.text-center]
+.A simple bucket group approach
+image::bucket-groups.png[align=center]
+
+An array of "buckets" is allocated and each bucket in turn points to its own individual linked list. This makes meeting the standard requirements of bucket iteration straight-forward. Unfortunately, iteration of the entire container is often times slow using this layout as each bucket must be examined for occupancy, yielding a time complexity of `O(bucket_count() + size())` when the standard requires complexity to be `O(size())`.
+
+Canonical standard implementations will wind up looking like the diagram below:
+
+[.text-center]
+.The canonical standard approach
+image::singly-linked.png[align=center,link=../diagrams/singly-linked.png,window=_blank]
+
+It's worth noting that this approach is only used by pass:[libc++] and pass:[libstdc++]; the MSVC Dinkumware implementation uses a different one. A more detailed analysis of the standard containers can be found http://bannalia.blogspot.com/2013/10/implementation-of-c-unordered.html[here].
+
+This unusually laid out data structure is chosen to make iteration of the entire container efficient by inter-connecting all of the nodes into a singly-linked list. One might also notice that buckets point to the node _before_ the start of the bucket's elements. This is done so that removing elements from the list can be done efficiently without introducing the need for a doubly-linked list. Unfortunately, this data structure introduces a guaranteed extra indirection. For example, to access the first element of a bucket, something like this must be done:
+
+```c++
+auto const idx = get_bucket_idx(hash_function(key));
+node* p = buckets[idx]; // first load
+node* n = p->next; // second load
+if (n && is_in_bucket(n, idx)) {
+  value_type const& v = *n; // third load
+  // ...
+}
+```
+
+With a simple bucket group layout, this is all that must be done:
+```c++
+auto const idx = get_bucket_idx(hash_function(key));
+node* n = buckets[idx]; // first load
+if (n) {
+  value_type const& v = *n; // second load
+  // ...
+}
+```
+
+In practice, the extra indirection can have a dramatic performance impact to common operations such as `insert`, `find` and `erase`. But to keep iteration of the container fast, Boost.Unordered introduces a novel data structure, a "bucket group". A bucket group is a fixed-width view of a subsection of the buckets array. It contains a bitmask (a `std::size_t`) which it uses to track occupancy of buckets and contains two pointers so that it can form a doubly-linked list with non-empty groups. An example diagram is below:
+
+[#img-fca-layout]
+.The new layout used by Boost
+image::fca.png[align=center]
+
+Thus container-wide iteration is turned into traversing the non-empty bucket groups (an operation with constant time complexity) which reduces the time complexity back to `O(size())`. In total, a bucket group is only 4 words in size and it views `sizeof(std::size_t) * CHAR_BIT` buckets meaning that for all common implementations, there's only 4 bits of space overhead per bucket introduced by the bucket groups.
+
+For more information on implementation rationale, read the <<Implementation Rationale, corresponding section>>.

doc/unordered/changes.adoc

@@ -1,158 +1,232 @@
+[#changes]
+= Change Log
 
-[/ Copyright 2008 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
+:idprefix: changes_
+:svn-ticket-url: https://svn.boost.org/trac/boost/ticket
+:github-pr-url: https://github.com/boostorg/unordered/pull
+:cpp: C++
 
-[template ticket[number]'''<ulink
-    url="https://svn.boost.org/trac/boost/ticket/'''[number]'''">'''#[number]'''</ulink>''']
+== Release 1.80.0 - Major update
 
-[template pull_request[number][@https://github.com/boostorg/unordered/pull/[number] GitHub #[number]]]
+* Refactor internal implementation to be dramatically faster
+* Allow `final` Hasher and KeyEqual objects
+* Update documentation, adding benchmark graphs and notes on the new internal 
+  data structures
 
-[section:changes Change Log]
+== Release 1.79.0
 
-[h2 Review Version]
+* Improved {cpp}20 support:
+  ** All containers have been updated to support 
+    heterogeneous `count`, `equal_range` and `find`.
+  ** All containers now implement the member function `contains`.
+  ** `erase_if` has been implemented for all containers.
+* Improved {cpp}23 support:
+  ** All containers have been updated to support
+    heterogeneous `erase` and `extract`.
+* Changed behavior of `reserve` to eagerly 
+  allocate ({github-pr-url}/59[PR#59^]).
+* Various warning fixes in the test suite.
+* Update code to internally use `boost::allocator_traits`.
+* Switch to Fibonacci hashing.
+* Update documentation to be written in AsciiDoc instead of QuickBook.
 
-Initial review version, for the review conducted from 7th December 2007 to
-16th December 2007.
+== Release 1.67.0
 
-[h2 1.35.0 Add-on - 31st March 2008]
+* Improved {cpp}17 support:
+  ** Add template deduction guides from the standard.
+  ** Use a simple implementation of `optional` in node handles, so
+    that they're closer to the standard.
+  ** Add missing `noexcept` specifications to `swap`, `operator=`
+    and node handles, and change the implementation to match.
+    Using `std::allocator_traits::is_always_equal`, or our own
+    implementation when not available, and
+    `boost::is_nothrow_swappable` in the implementation.
+* Improved {cpp}20 support:
+  ** Use `boost::to_address`, which has the proposed {cpp}20 semantics,
+    rather than the old custom implementation.
+* Add `element_type` to iterators, so that `std::pointer_traits`
+  will work.
+* Use `std::piecewise_construct` on recent versions of Visual {cpp},
+  and other uses of the Dinkumware standard library,
+  now using Boost.Predef to check compiler and library versions.
+* Use `std::iterator_traits` rather than the boost iterator traits
+  in order to remove dependency on Boost.Iterator.
+* Remove iterators' inheritance from `std::iterator`, which is
+  deprecated in {cpp}17, thanks to Daniela Engert
+  ({github-pr-url}/7[PR#7^]).
+* Stop using `BOOST_DEDUCED_TYPENAME`.
+* Update some Boost include paths.
+* Rename some internal methods, and variables.
+* Various testing improvements.
+* Miscellaneous internal changes.
 
-Unofficial release uploaded to vault, to be used with Boost 1.35.0. Incorporated
-many of the suggestions from the review.
+== Release 1.66.0
 
-* Improved portability thanks to Boost regression testing.
-* Fix lots of typos, and clearer text in the documentation.
-* Fix floating point to `std::size_t` conversion when calculating sizes from
-  the max load factor, and use `double` in the calculation for greater accuracy.
-* Fix some errors in the examples.
+* Simpler move construction implementation.
+* Documentation fixes ({github-pr-url}/6[GitHub #6^]).
 
-[h2 Boost 1.36.0]
+== Release 1.65.0
 
-First official release.
+* Add deprecated attributes to `quick_erase` and `erase_return_void`.
+  I really will remove them in a future version this time.
+* Small standards compliance fixes:
+  ** `noexpect` specs for `swap` free functions.
+  ** Add missing `insert(P&&)` methods.
 
-* Rearrange the internals.
-* Move semantics - full support when rvalue references are available, emulated
-  using a cut down version of the Adobe move library when they are not.
-* Emplace support when rvalue references and variadic template are available.
-* More efficient node allocation when rvalue references and variadic template
-  are available.
-* Added equality operators.
+== Release 1.64.0
 
-[h2 Boost 1.37.0]
+* Initial support for new {cpp}17 member functions:
+  `insert_or_assign` and `try_emplace` in `unordered_map`,
+* Initial support for `merge` and `extract`.
+  Does not include transferring nodes between
+  `unordered_map` and `unordered_multimap` or between `unordered_set` and
+  `unordered_multiset` yet. That will hopefully be in the next version of
+  Boost.
 
-* Rename overload of `emplace` with hint, to `emplace_hint` as specified in
-  [@http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2008/n2691.pdf n2691].
-* Provide forwarding headers at `<boost/unordered/unordered_map_fwd.hpp>` and
-  `<boost/unordered/unordered_set_fwd.hpp>`.
-* Move all the implementation inside `boost/unordered`, to assist
-  modularization and hopefully make it easier to track changes in subversion.
+== Release 1.63.0
 
-[h2 Boost 1.38.0]
+* Check hint iterator in `insert`/`emplace_hint`.
+* Fix some warnings, mostly in the tests.
+* Manually write out `emplace_args` for small numbers of arguments -
+  should make template error messages a little more bearable.
+* Remove superfluous use of `boost::forward` in emplace arguments,
+  which fixes emplacing string literals in old versions of Visual {cpp}.
+* Fix an exception safety issue in assignment. If bucket allocation
+  throws an exception, it can overwrite the hash and equality functions while
+  leaving the existing elements in place. This would mean that the function
+  objects wouldn't match the container elements, so elements might be in the
+  wrong bucket and equivalent elements would be incorrectly handled.
+* Various reference documentation improvements.
+* Better allocator support ({svn-ticket-url}/12459[#12459^]).
+* Make the no argument constructors implicit.
+* Implement missing allocator aware constructors.
+* Fix assigning the hash/key equality functions for empty containers.
+* Remove unary/binary_function from the examples in the documentation.
+  They are removed in {cpp}17.
+* Support 10 constructor arguments in emplace. It was meant to support up to 10
+  arguments, but an off by one error in the preprocessor code meant it only
+  supported up to 9.
 
-* Use [@boost:/libs/core/swap.html `boost::swap`].
-* [@https://svn.boost.org/trac/boost/ticket/2237 Ticket 2237]:
-  Document that the equality and inequality operators are undefined for two
-  objects if their equality predicates aren't equivalent. Thanks to Daniel
-  Krügler.
-* [@https://svn.boost.org/trac/boost/ticket/1710 Ticket 1710]:
-  Use a larger prime number list. Thanks to Thorsten Ottosen and Hervé
-  Brönnimann.
-* Use
-  [@boost:/libs/type_traits/doc/html/boost_typetraits/category/alignment.html
-  aligned storage] to store the types. This changes the way the allocator is
-  used to construct nodes. It used to construct the node with two calls to
-  the allocator's `construct` method - once for the pointers and once for the
-  value. It now constructs the node with a single call to construct and
-  then constructs the value using in place construction.
-* Add support for C++0x initializer lists where they're available (currently
-  only g++ 4.4 in C++0x mode).
+== Release 1.62.0
 
-[h2 Boost 1.39.0]
+* Remove use of deprecated `boost::iterator`.
+* Remove `BOOST_NO_STD_DISTANCE` workaround.
+* Remove `BOOST_UNORDERED_DEPRECATED_EQUALITY` warning.
+* Simpler implementation of assignment, fixes an exception safety issue
+  for `unordered_multiset` and `unordered_multimap`. Might be a little slower.
+* Stop using return value SFINAE which some older compilers have issues
+  with.
 
-* [@https://svn.boost.org/trac/boost/ticket/2756 Ticket 2756]: Avoid a warning
-  on Visual C++ 2009.
-* Some other minor internal changes to the implementation, tests and
-  documentation.
-* Avoid an unnecessary copy in `operator[]`.
-* [@https://svn.boost.org/trac/boost/ticket/2975 Ticket 2975]: Fix length of
-  prime number list.
+== Release 1.58.0
 
-[h2 Boost 1.40.0]
+* Remove unnecessary template parameter from const iterators.
+* Rename private `iterator` typedef in some iterator classes, as it
+  confuses some traits classes.
+* Fix move assignment with stateful, propagate_on_container_move_assign
+  allocators ({svn-ticket-url}/10777[#10777^]).
+* Fix rare exception safety issue in move assignment.
+* Fix potential overflow when calculating number of buckets to allocate
+  ({github-pr-url}/4[GitHub #4^]).
 
-* [@https://svn.boost.org/trac/boost/ticket/2975 Ticket 2975]:
-  Store the prime list as a preprocessor sequence - so that it will always get
-  the length right if it changes again in the future.
-* [@https://svn.boost.org/trac/boost/ticket/1978 Ticket 1978]:
-  Implement `emplace` for all compilers.
-* [@https://svn.boost.org/trac/boost/ticket/2908 Ticket 2908],
-  [@https://svn.boost.org/trac/boost/ticket/3096 Ticket 3096]:
-  Some workarounds for old versions of borland, including adding explicit
-  destructors to all containers.
-* [@https://svn.boost.org/trac/boost/ticket/3082 Ticket 3082]:
-  Disable incorrect Visual C++ warnings.
-* Better configuration for C++0x features when the headers aren't available.
-* Create less buckets by default.
+== Release 1.57.0
 
-[h2 Boost 1.41.0 - Major update]
+* Fix the `pointer` typedef in iterators ({svn-ticket-url}/10672[#10672^]).
+* Fix Coverity warning
+  ({github-pr-url}/2[GitHub #2^]).
 
-* The original version made heavy use of macros to sidestep some of the older
-  compilers' poor template support. But since I no longer support those
-  compilers and the macro use was starting to become a maintenance burden it
-  has been rewritten to use templates instead of macros for the implementation
-  classes.
+== Release 1.56.0
 
-* The container object is now smaller thanks to using `boost::compressed_pair`
-  for EBO and a slightly different function buffer - now using a bool instead
-  of a member pointer.
+* Fix some shadowed variable warnings ({svn-ticket-url}/9377[#9377^]).
+* Fix allocator use in documentation ({svn-ticket-url}/9719[#9719^]).
+* Always use prime number of buckets for integers. Fixes performance
+  regression when inserting consecutive integers, although makes other
+  uses slower ({svn-ticket-url}/9282[#9282^]).
+* Only construct elements using allocators, as specified in {cpp}11 standard.
 
-* Buckets are allocated lazily which means that constructing an empty container
-  will not allocate any memory.
+== Release 1.55.0
 
-[h2 Boost 1.42.0]
+* Avoid some warnings ({svn-ticket-url}/8851[#8851^], {svn-ticket-url}/8874[#8874^]).
+* Avoid exposing some detail functions via. ADL on the iterators.
+* Follow the standard by only using the allocators' construct and destroy
+  methods to construct and destroy stored elements. Don't use them for internal
+  data like pointers.
 
-* Support instantiating the containers with incomplete value types.
-* Reduced the number of warnings (mostly in tests).
-* Improved codegear compatibility.
-* [@http://svn.boost.org/trac/boost/ticket/3693 Ticket 3693]:
-  Add `erase_return_void` as a temporary workaround for the current
-  `erase` which can be inefficient because it has to find the next
-  element to return an iterator.
-* Add templated find overload for compatible keys.
-* [@http://svn.boost.org/trac/boost/ticket/3773 Ticket 3773]:
-  Add missing `std` qualifier to `ptrdiff_t`.
-* Some code formatting changes to fit almost all lines into 80 characters.
+== Release 1.54.0
 
-[h2 Boost 1.43.0]
+* Mark methods specified in standard as `noexpect`. More to come in the next
+  release.
+* If the hash function and equality predicate are known to both have nothrow
+  move assignment or construction then use them.
 
-* [@http://svn.boost.org/trac/boost/ticket/3966 Ticket 3966]:
-  `erase_return_void` is now `quick_erase`, which is the
-  [@http://home.roadrunner.com/~hinnant/issue_review/lwg-active.html#579
-  current forerunner for resolving the slow erase by iterator], although
-  there's a strong possibility that this may change in the future. The old
-  method name remains for backwards compatibility but is considered deprecated
-  and will be removed in a future release.
-* Use Boost.Exception.
-* Stop using deprecated `BOOST_HAS_*` macros.
+== Release 1.53.0
 
-[h2 Boost 1.45.0]
+* Remove support for the old pre-standard variadic pair constructors, and
+  equality implementation. Both have been deprecated since Boost 1.48.
+* Remove use of deprecated config macros.
+* More internal implementation changes, including a much simpler
+  implementation of `erase`.
 
-* Fix a bug when inserting into an `unordered_map` or `unordered_set` using
-  iterators which returns `value_type` by copy.
+== Release 1.52.0
 
-[h2 Boost 1.48.0 - Major update]
+* Faster assign, which assigns to existing nodes where possible, rather than
+  creating entirely new nodes and copy constructing.
+* Fixed bug in `erase_range` ({svn-ticket-url}/7471[#7471^]).
+* Reverted some of the internal changes to how nodes are created, especially
+  for {cpp}11 compilers. 'construct' and 'destroy' should work a little better
+  for {cpp}11 allocators.
+* Simplified the implementation a bit. Hopefully more robust.
+
+== Release 1.51.0
+
+* Fix construction/destruction issue when using a {cpp}11 compiler with a
+  {cpp}03 allocator ({svn-ticket-url}/7100[#7100^]).
+* Remove a `try..catch` to support compiling without exceptions.
+* Adjust SFINAE use to try to support g++ 3.4 ({svn-ticket-url}/7175[#7175^]).
+* Updated to use the new config macros.
+
+== Release 1.50.0
+
+* Fix equality for `unordered_multiset` and `unordered_multimap`.
+* {svn-ticket-url}/6857[Ticket 6857^]:
+  Implement `reserve`.
+* {svn-ticket-url}/6771[Ticket 6771^]:
+  Avoid gcc's `-Wfloat-equal` warning.
+* {svn-ticket-url}/6784[Ticket 6784^]:
+  Fix some Sun specific code.
+* {svn-ticket-url}/6190[Ticket 6190^]:
+  Avoid gcc's `-Wshadow` warning.
+* {svn-ticket-url}/6905[Ticket 6905^]:
+  Make namespaces in macros compatible with `bcp` custom namespaces.
+  Fixed by Luke Elliott.
+* Remove some of the smaller prime number of buckets, as they may make
+  collisions quite probable (e.g. multiples of 5 are very common because
+  we used base 10).
+* On old versions of Visual {cpp}, use the container library's implementation
+  of `allocator_traits`, as it's more likely to work.
+* On machines with 64 bit std::size_t, use power of 2 buckets, with Thomas
+  Wang's hash function to pick which one to use. As modulus is very slow
+  for 64 bit values.
+* Some internal changes.
+
+== Release 1.49.0
+
+* Fix warning due to accidental odd assignment.
+* Slightly better error messages.
+
+== Release 1.48.0 - Major update
 
 This is major change which has been converted to use Boost.Move's move
-emulation, and be more compliant with the C++11 standard. See the
-[link unordered.compliance compliance section] for details.
+emulation, and be more compliant with the {cpp}11 standard. See the
+xref:unordered.adoc#compliance[compliance section] for details.
 
-The container now meets C++11's complexity requirements, but to do so
+The container now meets {cpp}11's complexity requirements, but to do so
 uses a little more memory. This means that `quick_erase` and
 `erase_return_void` are no longer required, they'll be removed in a
 future version.
 
-C++11 support has resulted in some breaking changes:
+{cpp}11 support has resulted in some breaking changes:
 
-* Equality comparison has been changed to the C++11 specification.
+* Equality comparison has been changed to the {cpp}11 specification.
   In a container with equivalent keys, elements in a group with equal
   keys used to have to be in the same order to be considered equal,
   now they can be a permutation of each other. To use the old
@@ -168,193 +242,140 @@ C++11 support has resulted in some breaking changes:
   pointers, rather than the allocator's `pointer` type.
 
 * `emplace` used to emulate the variadic pair constructors that
-  appeared in early C++0x drafts. Since they were removed it no
+  appeared in early {cpp}0x drafts. Since they were removed it no
   longer does so. It does emulate the new `piecewise_construct`
   pair constructors - only you need to use
   `boost::piecewise_construct`. To use the old emulation of
   the variadic constructors define
   `BOOST_UNORDERED_DEPRECATED_PAIR_CONSTRUCT`.
 
-[h2 Boost 1.49.0]
+== Release 1.45.0
 
-* Fix warning due to accidental odd assignment.
-* Slightly better error messages.
+* Fix a bug when inserting into an `unordered_map` or `unordered_set` using
+  iterators which returns `value_type` by copy.
 
-[h2 Boost 1.50.0]
+== Release 1.43.0
 
-* Fix equality for `unordered_multiset` and `unordered_multimap`.
-* [@https://svn.boost.org/trac/boost/ticket/6857 Ticket 6857]:
-  Implement `reserve`.
-* [@https://svn.boost.org/trac/boost/ticket/6771 Ticket 6771]:
-  Avoid gcc's `-Wfloat-equal` warning.
-* [@https://svn.boost.org/trac/boost/ticket/6784 Ticket 6784]:
-  Fix some Sun specific code.
-* [@https://svn.boost.org/trac/boost/ticket/6190 Ticket 6190]:
-  Avoid gcc's `-Wshadow` warning.
-* [@https://svn.boost.org/trac/boost/ticket/6905 Ticket 6905]:
-  Make namespaces in macros compatible with `bcp` custom namespaces.
-  Fixed by Luke Elliott.
-* Remove some of the smaller prime number of buckets, as they may make
-  collisions quite probable (e.g. multiples of 5 are very common because
-  we used base 10).
-* On old versions of Visual C++, use the container library's implementation
-  of `allocator_traits`, as it's more likely to work.
-* On machines with 64 bit std::size_t, use power of 2 buckets, with Thomas
-  Wang's hash function to pick which one to use. As modulus is very slow
-  for 64 bit values.
-* Some internal changes.
+* {svn-ticket-url}/3966[Ticket 3966^]:
+  `erase_return_void` is now `quick_erase`, which is the
+  http://home.roadrunner.com/~hinnant/issue_review/lwg-active.html#579[
+  current forerunner for resolving the slow erase by iterator^], although
+  there's a strong possibility that this may change in the future. The old
+  method name remains for backwards compatibility but is considered deprecated
+  and will be removed in a future release.
+* Use Boost.Exception.
+* Stop using deprecated `BOOST_HAS_*` macros.
 
-[h2 Boost 1.51.0]
+== Release 1.42.0
 
-* Fix construction/destruction issue when using a C++11 compiler with a
-  C++03 allocator ([ticket 7100]).
-* Remove a `try..catch` to support compiling without exceptions.
-* Adjust SFINAE use to try to support g++ 3.4 ([ticket 7175]).
-* Updated to use the new config macros.
+* Support instantiating the containers with incomplete value types.
+* Reduced the number of warnings (mostly in tests).
+* Improved codegear compatibility.
+* {svn-ticket-url}/3693[Ticket 3693^]:
+  Add `erase_return_void` as a temporary workaround for the current
+  `erase` which can be inefficient because it has to find the next
+  element to return an iterator.
+* Add templated find overload for compatible keys.
+* {svn-ticket-url}/3773[Ticket 3773^]:
+  Add missing `std` qualifier to `ptrdiff_t`.
+* Some code formatting changes to fit almost all lines into 80 characters.
 
-[h2 Boost 1.52.0]
+== Release 1.41.0 - Major update
 
-* Faster assign, which assigns to existing nodes where possible, rather than
-  creating entirely new nodes and copy constructing.
-* Fixed bug in `erase_range` ([ticket 7471]).
-* Reverted some of the internal changes to how nodes are created, especially
-  for C++11 compilers. 'construct' and 'destroy' should work a little better
-  for C++11 allocators.
-* Simplified the implementation a bit. Hopefully more robust.
+* The original version made heavy use of macros to sidestep some of the older
+  compilers' poor template support. But since I no longer support those
+  compilers and the macro use was starting to become a maintenance burden it
+  has been rewritten to use templates instead of macros for the implementation
+  classes.
 
-[h2 Boost 1.53.0]
+* The container object is now smaller thanks to using `boost::compressed_pair`
+  for EBO and a slightly different function buffer - now using a bool instead
+  of a member pointer.
 
-* Remove support for the old pre-standard variadic pair constructors, and
-  equality implementation. Both have been deprecated since Boost 1.48.
-* Remove use of deprecated config macros.
-* More internal implementation changes, including a much simpler
-  implementation of `erase`.
+* Buckets are allocated lazily which means that constructing an empty container
+  will not allocate any memory.
 
-[h2 Boost 1.54.0]
+== Release 1.40.0
 
-* Mark methods specified in standard as `noexpect`. More to come in the next
-  release.
-* If the hash function and equality predicate are known to both have nothrow
-  move assignment or construction then use them.
+* {svn-ticket-url}/2975[Ticket 2975^]:
+  Store the prime list as a preprocessor sequence - so that it will always get
+  the length right if it changes again in the future.
+* {svn-ticket-url}/1978[Ticket 1978^]:
+  Implement `emplace` for all compilers.
+* {svn-ticket-url}/2908[Ticket 2908^],
+  {svn-ticket-url}/3096[Ticket 3096^]:
+  Some workarounds for old versions of borland, including adding explicit
+  destructors to all containers.
+* {svn-ticket-url}/3082[Ticket 3082^]:
+  Disable incorrect Visual {cpp} warnings.
+* Better configuration for {cpp}0x features when the headers aren't available.
+* Create less buckets by default.
 
-[h2 Boost 1.55.0]
+== Release 1.39.0
 
-* Avoid some warnings ([ticket 8851], [ticket 8874]).
-* Avoid exposing some detail functions via. ADL on the iterators.
-* Follow the standard by only using the allocators' construct and destroy
-  methods to construct and destroy stored elements. Don't use them for internal
-  data like pointers.
+* {svn-ticket-url}/2756[Ticket 2756^]: Avoid a warning
+  on Visual {cpp} 2009.
+* Some other minor internal changes to the implementation, tests and
+  documentation.
+* Avoid an unnecessary copy in `operator[]`.
+* {svn-ticket-url}/2975[Ticket 2975^]: Fix length of
+  prime number list.
 
-[h2 Boost 1.56.0]
+== Release 1.38.0
 
-* Fix some shadowed variable warnings ([ticket 9377]).
-* Fix allocator use in documentation ([ticket 9719]).
-* Always use prime number of buckets for integers. Fixes performance
-  regression when inserting consecutive integers, although makes other
-  uses slower ([ticket 9282]).
-* Only construct elements using allocators, as specified in C++11 standard.
+* Use link:../../../core/swap.html[`boost::swap`^].
+* {svn-ticket-url}/2237[Ticket 2237^]:
+  Document that the equality and inequality operators are undefined for two
+  objects if their equality predicates aren't equivalent. Thanks to Daniel
+  Krügler.
+* {svn-ticket-url}/1710[Ticket 1710^]:
+  Use a larger prime number list. Thanks to Thorsten Ottosen and Hervé
+  Brönnimann.
+* Use
+  link:../../../type_traits/index.html[aligned storage^] to store the types.
+  This changes the way the allocator is used to construct nodes. It used to
+  construct the node with two calls to the allocator's `construct`
+  method - once for the pointers and once for the value. It now constructs
+  the node with a single call to construct and then constructs the value using
+  in place construction.
+* Add support for {cpp}0x initializer lists where they're available (currently
+  only g++ 4.4 in {cpp}0x mode).
 
-[h2 Boost 1.57.0]
+== Release 1.37.0
 
-* Fix the `pointer` typedef in iterators ([ticket 10672]).
-* Fix Coverity warning
-  ([@https://github.com/boostorg/unordered/pull/2 GitHub #2]).
+* Rename overload of `emplace` with hint, to `emplace_hint` as specified in
+  http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2008/n2691.pdf[n2691^].
+* Provide forwarding headers at `<boost/unordered/unordered_map_fwd.hpp>` and
+  `<boost/unordered/unordered_set_fwd.hpp>`.
+* Move all the implementation inside `boost/unordered`, to assist
+  modularization and hopefully make it easier to track Release subversion.
 
-[h2 Boost 1.58.0]
+== Release 1.36.0
 
-* Remove unnecessary template parameter from const iterators.
-* Rename private `iterator` typedef in some iterator classes, as it
-  confuses some traits classes.
-* Fix move assignment with stateful, propagate_on_container_move_assign
-  allocators ([ticket 10777]).
-* Fix rare exception safety issue in move assignment.
-* Fix potential overflow when calculating number of buckets to allocate
-  ([@https://github.com/boostorg/unordered/pull/4 GitHub #4]).
+First official release.
 
-[h2 Boost 1.62.0]
+* Rearrange the internals.
+* Move semantics - full support when rvalue references are available, emulated
+  using a cut down version of the Adobe move library when they are not.
+* Emplace support when rvalue references and variadic template are available.
+* More efficient node allocation when rvalue references and variadic template
+  are available.
+* Added equality operators.
 
-* Remove use of deprecated `boost::iterator`.
-* Remove `BOOST_NO_STD_DISTANCE` workaround.
-* Remove `BOOST_UNORDERED_DEPRECATED_EQUALITY` warning.
-* Simpler implementation of assignment, fixes an exception safety issue
-  for `unordered_multiset` and `unordered_multimap`. Might be a little slower.
-* Stop using return value SFINAE which some older compilers have issues
-  with.
+== Boost 1.35.0 Add-on - 31st March 2008
 
-[h2 Boost 1.63.0]
+Unofficial release uploaded to vault, to be used with Boost 1.35.0. Incorporated
+many of the suggestions from the review.
 
-* Check hint iterator in `insert`/`emplace_hint`.
-* Fix some warnings, mostly in the tests.
-* Manually write out `emplace_args` for small numbers of arguments -
-  should make template error messages a little more bearable.
-* Remove superfluous use of `boost::forward` in emplace arguments,
-  which fixes emplacing string literals in old versions of Visual C++.
-* Fix an exception safety issue in assignment. If bucket allocation
-  throws an exception, it can overwrite the hash and equality functions while
-  leaving the existing elements in place. This would mean that the function
-  objects wouldn't match the container elements, so elements might be in the
-  wrong bucket and equivalent elements would be incorrectly handled.
-* Various reference documentation improvements.
-* Better allocator support ([ticket 12459]).
-* Make the no argument constructors implicit.
-* Implement missing allocator aware constructors.
-* Fix assigning the hash/key equality functions for empty containers.
-* Remove unary/binary_function from the examples in the documentation.
-  They are removed in C++17.
-* Support 10 constructor arguments in emplace. It was meant to support up to 10
-  arguments, but an off by one error in the preprocessor code meant it only
-  supported up to 9.
+* Improved portability thanks to Boost regression testing.
+* Fix lots of typos, and clearer text in the documentation.
+* Fix floating point to `std::size_t` conversion when calculating sizes from
+  the max load factor, and use `double` in the calculation for greater accuracy.
+* Fix some errors in the examples.
 
-[h2 Boost 1.64.0]
-* Initial support for new C++17 member functions:
-  `insert_or_assign` and `try_emplace` in `unordered_map`,
-* Initial support for `merge` and `extract`.
-  Does not include transferring nodes between
-  `unordered_map` and `unordered_multimap` or between `unordered_set` and
-  `unordered_multiset` yet. That will hopefully be in the next version of
-  Boost.
+== Review Version
 
-[h2 Boost 1.65.0]
+Initial review version, for the review conducted from 7th December 2007 to
+16th December 2007.
 
-* Add deprecated attributes to `quick_erase` and `erase_return_void`.
-  I really will remove them in a future version this time.
-* Small standards compliance fixes:
-  * `noexpect` specs for `swap` free functions.
-  * Add missing `insert(P&&)` methods.
 
-[h2 Boost 1.66.0]
-
-* Simpler move construction implementation.
-* Documentation fixes ([pull_request 6]).
-
-[h2 Boost 1.67.0]
-
-* Improved C++17 support:
-  * Add template deduction guides from the standard.
-  * Use a simple implementation of `optional` in node handles, so
-    that they're closer to the standard.
-  * Add missing `noexcept` specifications to `swap`, `operator=`
-    and node handles, and change the implementation to match.
-    Using `std::allocator_traits::is_always_equal`, or our own
-    implementation when not available, and
-    `boost::is_nothrow_swappable` in the implementation.
-* Improved C++20 support:
-  * Use `boost::to_address`, which has the proposed C++20 semantics,
-    rather than the old custom implementation.
-* Add `element_type` to iterators, so that `std::pointer_traits`
-  will work.
-* Use `std::piecewise_construct` on recent versions of Visual C++,
-  and other uses of the Dinkumware standard library,
-  now using Boost.Predef to check compiler and library versions.
-* Use `std::iterator_traits` rather than the boost iterator traits
-  in order to remove dependency on Boost.Iterator.
-* Remove iterators' inheritance from `std::iterator`, which is
-  deprecated in C++17, thanks to Daniela Engert
-  ([@https://github.com/boostorg/unordered/pull/7 PR#7]).
-* Stop using `BOOST_DEDUCED_TYPENAME`.
-* Update some Boost include paths.
-* Rename some internal methods, and variables.
-* Various testing improvements.
-* Miscellaneous internal changes.
-
-[endsect]

doc/unordered/comparison.adoc

@@ -0,0 +1,112 @@
+[#comparison]
+
+:idprefix: comparison_
+
+= Comparison with Associative Containers
+
+[caption=, title='Table {counter:table-counter} Interface differences']
+[cols="1,1", frame=all, grid=rows]
+|===
+|Associative Containers |Unordered Associative Containers
+
+|Parameterized by an ordering relation `Compare`
+|Parameterized by a function object `Hash` and an equivalence relation `Pred`
+
+|Keys can be compared using `key_compare` which is accessed by member function `key_comp()`, values can be compared using `value_compare` which is accessed by member function `value_comp()`.
+|Keys can be hashed using `hasher` which is accessed by member function `hash_function()`, and checked for equality using `key_equal` which is accessed by member function `key_eq()`. There is no function object for compared or hashing values.
+
+|Constructors have optional extra parameters for the comparison object. 
+|Constructors have optional extra parameters for the initial minimum number of buckets, a hash function and an equality object.
+
+|Keys `k1`, `k2` are considered equivalent if `!Compare(k1, k2) && !Compare(k2, k1)`. 
+|Keys `k1`, `k2` are considered equivalent if `Pred(k1, k2)`
+
+|Member function `lower_bound(k)` and `upper_bound(k)`
+|No equivalent. Since the elements aren't ordered `lower_bound` and `upper_bound` would be meaningless.
+
+|`equal_range(k)` returns an empty range at the position that `k` would be inserted if `k` isn't present in the container.
+|`equal_range(k)` returns a range at the end of the container if `k` isn't present in the container. It can't return a positioned range as `k` could be inserted into multiple place. To find out the bucket that `k` would be inserted into use `bucket(k)`. But remember that an insert can cause the container to rehash - meaning that the element can be inserted into a different bucket.
+
+|`iterator`, `const_iterator` are of the bidirectional category.
+|`iterator`, `const_iterator` are of at least the forward category.
+
+|Iterators, pointers and references to the container's elements are never invalidated.
+|<<buckets_iterator_invalidation,Iterators can be invalidated by calls to insert or rehash>>. Pointers and references to the container's elements are never invalidated.
+
+|Iterators iterate through the container in the order defined by the comparison object.
+|Iterators iterate through the container in an arbitrary order, that can change as elements are inserted, although equivalent elements are always adjacent.
+
+|No equivalent
+|Local iterators can be used to iterate through individual buckets. (The order of local iterators and iterators aren't required to have any correspondence.)
+
+|Can be compared using the `==`, `!=`, `<`, `\<=`, `>`, `>=` operators.
+|Can be compared using the `==` and `!=` operators.
+
+|
+|When inserting with a hint, implementations are permitted to ignore the hint.
+
+|`erase` never throws an exception
+|The containers' hash or predicate function can throw exceptions from `erase`.
+
+|===
+
+---
+
+[caption=, title='Table {counter:table-counter} Complexity Guarantees']
+[cols="1,1,1", frame=all, grid=rows]
+|===
+|Operation |Associative Containers |Unordered Associative Containers
+
+|Construction of empty container
+|constant
+|O(_n_) where _n_ is the minimum number of buckets.
+
+|Construction of container from a range of _N_ elements
+|O(_N log N_), O(_N_) if the range is sorted with `value_comp()`
+|Average case O(_N_), worst case O(_N^2^_)
+
+|Insert a single element
+|logarithmic
+|Average case constant, worst case linear
+
+|Insert a single element with a hint
+|Amortized constant if `t` elements inserted right after hint, logarithmic otherwise
+|Average case constant, worst case linear (ie. the same as a normal insert).
+
+|Inserting a range of _N_ elements
+|_N_ log(`size()` + _N_)
+|Average case O(_N_), worst case O(_N_ * `size()`)
+
+|Erase by key, `k`
+|O(log(`size()`) + `count(k)`)
+|Average case: O(`count(k)`), Worst case: O(`size()`)
+
+|Erase a single element by iterator
+|Amortized constant
+|Average case: O(1), Worst case: O(`size()`)
+
+|Erase a range of _N_ elements
+|O(log(`size()`) + _N_)
+|Average case: O(_N_), Worst case: O(`size()`)
+
+|Clearing the container
+|O(`size()`)
+|O(`size()`)
+
+|Find
+|logarithmic
+|Average case: O(1), Worst case: O(`size()`)
+
+|Count
+|O(log(`size()`) + `count(k)`)
+|Average case: O(1), Worst case: O(`size()`)
+
+|`equal_range(k)`
+|logarithmic
+|Average case: O(`count(k)`), Worst case: O(`size()`)
+
+|`lower_bound`,`upper_bound`
+|logarithmic
+|n/a
+
+|===

doc/unordered/compliance.adoc

@@ -1,16 +1,17 @@
-[/ Copyright 2011 Daniel James.
- / Distributed under the Boost Software License, Version 1.0. (See accompanying
- / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ]
+[#compliance]
+= Standard Compliance
 
-[section:compliance Standard Compliance]
+:idprefix: compliance_
+
+:cpp: C++
 
 The intent of Boost.Unordered is to implement a close (but imperfect)
-implementation of the C++17 standard, that will work with C++98 upwards.
+implementation of the {cpp}17 standard, that will work with {cpp}98 upwards.
 The wide compatibility does mean some comprimises have to be made.
-With a compiler and library that fully support C++11, the differences should
+With a compiler and library that fully support {cpp}11, the differences should
 be minor.
 
-[section:move Move emulation]
+== Move emulation
 
 Support for move semantics is implemented using Boost.Move. If rvalue
 references are available it will use them, but if not it uses a close,
@@ -22,11 +23,9 @@ but imperfect emulation. On such compilers:
 * The containers themselves are not movable.
 * Argument forwarding is not perfect.
 
-[endsect]
+== Use of allocators
 
-[section:allocator_compliance Use of allocators]
-
-C++11 introduced a new allocator system. It's backwards compatible due to
+{cpp}11 introduced a new allocator system. It's backwards compatible due to
 the lax requirements for allocators in the old standard, but might need
 some changes for allocators which worked with the old versions of the
 unordered containers.
@@ -57,11 +56,9 @@ Due to imperfect move emulation, some assignments might check
 `propagate_on_container_copy_assignment` on some compilers and
 `propagate_on_container_move_assignment` on others.
 
-[endsect]
+== Construction/Destruction using allocators
 
-[section:construction Construction/Destruction using allocators]
-
-The following support is required for full use of C++11 style
+The following support is required for full use of {cpp}11 style
 construction/destruction:
 
 * Variadic templates.
@@ -74,15 +71,12 @@ otherwise.
 
 When this is the case `allocator_traits::construct` and
 `allocator_traits::destroy` will always be used, apart from when piecewise
-constructing a `std::pair` using `boost::tuple` (see [link
-unordered.compliance.pairs below]), but that should be easily avoided.
+constructing a `std::pair` using `boost::tuple` (see <<compliance_pairs,below>>), but that should be easily avoided.
 
 When support is not available `allocator_traits::construct` and
 `allocator_traits::destroy` are never called.
 
-[endsect]
-
-[section:pointer_traits Pointer Traits]
+== Pointer Traits
 
 `pointer_traits` aren't used. Instead, pointer types are obtained from
 rebound allocators, this can cause problems if the allocator can't be
@@ -90,30 +84,28 @@ used with incomplete types. If `const_pointer` is not defined in the
 allocator, `boost::pointer_to_other<pointer, const value_type>::type`
 is used to obtain a const pointer.
 
-[endsect]
-
-[#unordered.compliance.pairs]
-[section:pairs Pairs]
+== Pairs
 
 Since the containers use `std::pair` they're limited to the version
-from the current standard library. But since C++11 `std::pair`'s
+from the current standard library. But since {cpp}11 ``std::pair``'s
 `piecewise_construct` based constructor is very useful, `emplace`
 emulates it with a `piecewise_construct` in the `boost::unordered`
 namespace. So for example, the following will work:
 
-    boost::unordered_multimap<std::string, std::complex> x;
+[source,c++]
+----
+boost::unordered_multimap<std::string, std::complex> x;
 
-    x.emplace(
-        boost::unordered::piecewise_construct,
-        boost::make_tuple("key"), boost::make_tuple(1, 2));
+x.emplace(
+    boost::unordered::piecewise_construct,
+    boost::make_tuple("key"), boost::make_tuple(1, 2));
+----
 
 Older drafts of the standard also supported variadic constructors
 for `std::pair`, where the first argument would be used for the
 first part of the pair, and the remaining for the second part.
 
-[endsect]
-
-[section:misc Miscellaneous]
+== Miscellaneous
 
 When swapping, `Pred` and `Hash` are not currently swapped by calling
 `swap`, their copy constructors are used. As a consequence when swapping
@@ -122,7 +114,3 @@ an exception may be thrown from their copy constructor.
 Variadic constructor arguments for `emplace` are only used when both
 rvalue references and variadic template parameters are available.
 Otherwise `emplace` can only take up to 10 constructors arguments.
-
-[endsect]
-
-[endsect]

doc/unordered/copyright.adoc

@@ -0,0 +1,14 @@
+[#copyright]
+= Copyright and License
+
+:idprefix: copyright_
+
+*Daniel James*
+
+Copyright (C) 2003, 2004 Jeremy B. Maitin-Shepard
+
+Copyright (C) 2005-2008 Daniel James
+
+Copyright (C) 2022 Christian Mazakas
+
+Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

doc/unordered/hash_equality.adoc

@@ -0,0 +1,149 @@
+[#hash_equality]
+
+:idprefix: hash_equality_
+
+= Equality Predicates and Hash Functions
+
+While the associative containers use an ordering relation to specify how the
+elements are stored, the unordered associative containers use an equality
+predicate and a hash function. For example, <<unordered_map,boost::unordered_map>>
+is declared as:
+
+```
+template <
+    class Key, class Mapped,
+    class Hash = boost::hash<Key>,
+    class Pred = std::equal_to<Key>,
+    class Alloc = std::allocator<std::pair<Key const, Mapped> > >
+class unordered_map;
+```
+
+The hash function comes first as you might want to change the hash function
+but not the equality predicate. For example, if you wanted to use the
+http://www.isthe.com/chongo/tech/comp/fnv/[FNV-1 hash^] you could write:
+
+```
+boost::unordered_map<std::string, int, hash::fnv_1>
+    dictionary;
+```
+
+There is an link:../../examples/fnv1.hpp[implementation of FNV-1^] in the examples directory.
+
+If you wish to use a different equality function, you will also need to use a matching hash function. For example, to implement a case insensitive dictionary you need to define a case insensitive equality predicate and hash function:
+
+```
+struct iequal_to
+{
+    bool operator()(std::string const& x,
+        std::string const& y) const
+    {
+        return boost::algorithm::iequals(x, y, std::locale());
+    }
+};
+
+struct ihash
+{
+    std::size_t operator()(std::string const& x) const
+    {
+        std::size_t seed = 0;
+        std::locale locale;
+
+        for(std::string::const_iterator it = x.begin();
+            it != x.end(); ++it)
+        {
+            boost::hash_combine(seed, std::toupper(*it, locale));
+        }
+
+        return seed;
+    }
+};
+```
+
+Which you can then use in a case insensitive dictionary:
+```
+boost::unordered_map<std::string, int, ihash, iequal_to>
+    idictionary;
+```
+
+This is a simplified version of the example at
+link:../../examples/case_insensitive.hpp[/libs/unordered/examples/case_insensitive.hpp^] which supports other locales and string types.
+
+CAUTION: Be careful when using the equality (`==`) operator with custom equality
+predicates, especially if you're using a function pointer. If you compare two
+containers with different equality predicates then the result is undefined.
+For most stateless function objects this is impossible - since you can only
+compare objects with the same equality predicate you know the equality
+predicates must be equal. But if you're using function pointers or a stateful
+equality predicate (e.g. `boost::function`) then you can get into trouble.
+
+== Custom Types
+
+Similarly, a custom hash function can be used for custom types:
+
+```
+struct point {
+    int x;
+    int y;
+};
+
+bool operator==(point const& p1, point const& p2)
+{
+    return p1.x == p2.x && p1.y == p2.y;
+}
+
+struct point_hash
+{
+    std::size_t operator()(point const& p) const
+    {
+        std::size_t seed = 0;
+        boost::hash_combine(seed, p.x);
+        boost::hash_combine(seed, p.y);
+        return seed;
+    }
+};
+
+boost::unordered_multiset<point, point_hash> points;
+```
+
+Since the default hash function is link:../../../container_hash/index.html[Boost.Hash^],
+we can extend it to support the type so that the hash function doesn't need to be explicitly given:
+
+```
+struct point {
+    int x;
+    int y;
+};
+
+bool operator==(point const& p1, point const& p2)
+{
+    return p1.x == p2.x && p1.y == p2.y;
+}
+
+std::size_t hash_value(point const& p) {
+    std::size_t seed = 0;
+    boost::hash_combine(seed, p.x);
+    boost::hash_combine(seed, p.y);
+    return seed;
+}
+
+// Now the default function objects work.
+boost::unordered_multiset<point> points;
+```
+
+See the link:../../../container_hash/index.html[Boost.Hash documentation^] for more detail on how to
+do this. Remember that it relies on extensions to the standard - so it
+won't work for other implementations of the unordered associative containers,
+you'll need to explicitly use Boost.Hash.
+
+[caption=, title='Table {counter:table-counter} Methods for accessing the hash and equality functions']
+[cols="1,.^1", frame=all, grid=rows]
+|===
+|Method |Description
+
+|`hasher hash_function() const` 
+|Returns the container's hash function.
+
+|`key_equal key_eq() const` 
+|Returns the container's key equality function..
+
+|===

doc/unordered/intro.adoc

@@ -0,0 +1,116 @@
+[#intro]
+= Introduction
+
+:idprefix: intro_
+:cpp: C++
+
+For accessing data based on key lookup, the {cpp} standard library offers `std::set`,
+`std::map`, `std::multiset` and `std::multimap`. These are generally
+implemented using balanced binary trees so that lookup time has
+logarithmic complexity. That is generally okay, but in many cases a
+link:https://en.wikipedia.org/wiki/Hash_table[hash table^] can perform better, as accessing data has constant complexity,
+on average. The worst case complexity is linear, but that occurs rarely and
+with some care, can be avoided.
+
+Also, the existing containers require a 'less than' comparison object
+to order their elements. For some data types this is impossible to implement
+or isn't practical. In contrast, a hash table only needs an equality function
+and a hash function for the key.
+
+With this in mind, unordered associative containers were added to the {cpp}
+standard. This is an implementation of the containers described in {cpp}11,
+with some <<compliance,deviations from the standard>> in
+order to work with non-{cpp}11 compilers and libraries.
+
+`unordered_set` and `unordered_multiset` are defined in the header
+`<boost/unordered_set.hpp>`
+[source,c++]
+----  
+namespace boost {
+    template <
+        class Key,
+        class Hash = boost::hash<Key>,
+        class Pred = std::equal_to<Key>,
+        class Alloc = std::allocator<Key> >
+    class unordered_set;
+
+    template<
+        class Key,
+        class Hash = boost::hash<Key>, 
+        class Pred = std::equal_to<Key>, 
+        class Alloc = std::allocator<Key> > 
+    class unordered_multiset;
+}
+----
+
+`unordered_map` and `unordered_multimap` are defined in the header
+`<boost/unordered_map.hpp>`
+
+[source,c++]
+----
+namespace boost {
+    template <
+        class Key, class Mapped,
+        class Hash = boost::hash<Key>,
+        class Pred = std::equal_to<Key>,
+        class Alloc = std::allocator<std::pair<Key const, Mapped> > >
+    class unordered_map;
+
+    template<
+        class Key, class Mapped,
+        class Hash = boost::hash<Key>,
+        class Pred = std::equal_to<Key>,
+        class Alloc = std::allocator<std::pair<Key const, Mapped> > >
+    class unordered_multimap;
+}
+----
+
+When using Boost.TR1, these classes are included from `<unordered_set>` and
+`<unordered_map>`, with the classes added to the `std::tr1` namespace.
+
+The containers are used in a similar manner to the normal associative
+containers:
+
+[source,cpp]
+----
+typedef boost::unordered_map<std::string, int> map;
+map x;
+x["one"] = 1;
+x["two"] = 2;
+x["three"] = 3;
+
+assert(x.at("one") == 1);
+assert(x.find("missing") == x.end());
+----
+
+But since the elements aren't ordered, the output of:
+
+[source,c++]
+----
+BOOST_FOREACH(map::value_type i, x) {
+    std::cout<<i.first<<","<<i.second<<"\n";
+}
+----
+
+can be in any order. For example, it might be:
+
+[source]
+----
+two,2
+one,1
+three,3
+----
+
+To store an object in an unordered associative container requires both a
+key equality function and a hash function. The default function objects in
+the standard containers support a few basic types including integer types,
+floating point types, pointer types, and the standard strings. Since
+Boost.Unordered uses link:../../../container_hash/index.html[boost::hash^] it also supports some other types,
+including standard containers. To use any types not supported by these methods
+you have to extend Boost.Hash to support the type or use
+your own custom equality predicates and hash functions. See the
+<<hash_equality,Equality Predicates and Hash Functions>> section
+for more details.
+
+There are other differences, which are listed in the
+<<comparison,Comparison with Associative Containers>> section.

doc/unordered/rationale.adoc

@@ -0,0 +1,72 @@
+[#rationale]
+
+:idprefix: rationale_
+
+= Implementation Rationale
+
+The intent of this library is to implement the unordered
+containers in the standard, so the interface was fixed. But there are
+still some implementation decisions to make. The priorities are
+conformance to the standard and portability.
+
+The http://en.wikipedia.org/wiki/Hash_table[Wikipedia article on hash tables^]
+has a good summary of the implementation issues for hash tables in general.
+
+== Data Structure
+
+By specifying an interface for accessing the buckets of the container the
+standard pretty much requires that the hash table uses chained addressing.
+
+It would be conceivable to write a hash table that uses another method. For
+example, it could use open addressing, and use the lookup chain to act as a
+bucket but there are some serious problems with this:
+
+* The standard requires that pointers to elements aren't invalidated, so
+  the elements can't be stored in one array, but will need a layer of
+  indirection instead - losing the efficiency and most of the memory gain,
+  the main advantages of open addressing.
+* Local iterators would be very inefficient and may not be able to
+  meet the complexity requirements.
+* There are also the restrictions on when iterators can be invalidated. Since
+  open addressing degrades badly when there are a high number of collisions the
+  restrictions could prevent a rehash when it's really needed. The maximum load
+  factor could be set to a fairly low value to work around this - but the
+  standard requires that it is initially set to 1.0.
+* And since the standard is written with a eye towards chained
+  addressing, users will be surprised if the performance doesn't reflect that.
+
+So chained addressing is used.
+
+== Number of Buckets
+
+There are two popular methods for choosing the number of buckets in a hash
+table. One is to have a prime number of buckets, another is to use a power
+of 2.
+
+Using a prime number of buckets, and choosing a bucket by using the modulus
+of the hash function's result will usually give a good result. The downside
+is that the required modulus operation is fairly expensive. This is what the
+containers used to do in most cases.
+
+Using a power of 2 allows for much quicker selection of the bucket to use,
+but at the expense of losing the upper bits of the hash value. For some
+specially designed hash functions it is possible to do this and still get a
+good result but as the containers can take arbitrary hash functions this can't
+be relied on.
+
+To avoid this a transformation could be applied to the hash function, for an
+example see
+http://web.archive.org/web/20121102023700/http://www.concentric.net/~Ttwang/tech/inthash.htm[Thomas Wang's article on integer hash functions^].
+Unfortunately, a transformation like Wang's requires knowledge of the number
+of bits in the hash value, so it was only used when `size_t` was 64 bit.
+
+Since release 1.79.0, https://en.wikipedia.org/wiki/Hash_function#Fibonacci_hashing[Fibonacci hashing]
+is used instead. With this implementation, the bucket number is determined
+by using `(h * m) >> (w - k)`, where `h` is the hash value, `m` is the golden
+ratio multiplied by `2^w`, `w` is the word size (32 or 64), and `2^k` is the
+number of buckets. This provides a good compromise between speed and
+distribution.
+
+Since release 1.80.0, prime numbers are chosen for the number of buckets in
+tandem with sophisticated modulo arithmetic. This removes the need for "mixing"
+the result of the user's hash function as was used for release 1.79.0.

doc/unordered/ref.adoc

@@ -0,0 +1,7 @@
+[#reference]
+= Reference
+
+include::unordered_map.adoc[]
+include::unordered_multimap.adoc[]
+include::unordered_set.adoc[]
+include::unordered_multiset.adoc[]

include/boost/unordered/detail/fca.hpp

@@ -0,0 +1,819 @@
+// Copyright (C) 2022 Joaquin M Lopez Munoz.
+// Copyright (C) 2022 Christian Mazakas
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_UNORDERED_DETAIL_FCA_HPP
+#define BOOST_UNORDERED_DETAIL_FCA_HPP
+
+/*
+
+The general structure of the fast closed addressing implementation is that we
+use straight-forward separate chaining (i.e. each bucket contains its own linked
+list) and then improve iteration time by adding an array of "bucket groups".
+
+A bucket group is a constant-width view into a subsection of the buckets array,
+containing a bitmask that indicates which one of the buckets in the subsection
+contains a list of nodes. This allows the code to test N buckets for occupancy
+in a single operation. Additional speed can be found by inter-linking occupied
+bucket groups with one another in a doubly-linked list. To this end, large
+swathes of the bucket groups array no longer need to be iterated and have their
+bitmasks examined for occupancy.
+
+A bucket group iterator contains a pointer to a bucket group along with a
+pointer into the buckets array. The iterator's bucket pointer is guaranteed to
+point to a bucket within the bucket group's view of the array. To advance the
+iterator, we need to determine if we need to skip to the next bucket group or
+simply move to the next occupied bucket as denoted by the bitmask.
+
+To accomplish this, we perform something roughly equivalent to this:
+```
+bucket_iterator itb = ...
+bucket_pointer p = itb.p
+bucket_group_pointer pbg = itb.pbg
+
+offset = p - pbg->buckets
+// because we wish to see if the _next_ bit in the mask is occupied, we'll
+// generate a testing mask from the current offset + 1
+//
+testing_mask = reset_first_bits(offset + 1)
+n = ctz(pbg->bitmask & testing_mask)
+
+if (n < N) {
+  p = pbg->buckets + n
+} else {
+  pbg = pbg->next
+  p = pbg->buckets + ctz(pbg->bitmask)
+}
+```
+
+`reset_first_bits` yields an unsigned integral with the first n bits set to 0
+and then by counting the number of trailing zeroes when AND'd against the bucket
+group's bitmask, we can derive the offset into the buckets array. When the
+calculated offset is equal to N, we know we've reached the end of a bucket group
+and we can advance to the next one.
+
+This is a rough explanation for how iterator incrementation should work for a
+fixed width size of N as 3 for the bucket groups
+```
+N = 3
+p = buckets
+pbg->bitmask = 0b101
+pbg->buckets = buckets
+
+offset = p - pbg->buckets // => 0
+testing_mask = reset_first_bits(offset + 1) // reset_first_bits(1) => 0b110
+
+x = bitmask & testing_mask // => 0b101 & 0b110 => 0b100
+ctz(x) // ctz(0b100) => 2
+// 2 < 3
+=> p = pbg->buckets + 2
+
+// increment again...
+offset = p - pbg->buckets // => 2
+testing_mask = reset_first_bits(offset + 1) // reset_first_bits(3) => 0b000
+
+bitmask & testing_mask // 0b101 & 0b000 => 0b000
+ctz(0b000) => 3
+// 3 < 3 is false now
+pbg = pbg->next
+initial_offset = ctz(pbg->bitmask)
+p = pbg->buckets + initial_offset
+```
+
+For `size_` number of buckets, there are `1 + (size_ / N)` bucket groups where
+`N` is the width of a bucket group, determined at compile-time.
+
+We allocate space for `size_ + 1` buckets, using the last one as a dummy bucket
+which is kept permanently empty so it can act as a sentinel value in the
+implementation of `iterator end();`. We set the last bucket group to act as a
+sentinel.
+
+```
+num_groups = size_ / N + 1
+groups = allocate(num_groups)
+pbg = groups + (num_groups - 1)
+
+// not guaranteed to point to exactly N buckets
+pbg->buckets = buckets + N * (size_ / N)
+
+// this marks the true end of the bucket array
+buckets pbg->bitmask = set_bit(size_ % N)
+
+// links in on itself
+pbg->next = pbg->prev = pbg
+```
+
+To this end, we can devise a safe iteration scheme while also creating a useful
+sentinel to use as the end iterator.
+
+Otherwise, usage of the data structure is relatively straight-forward compared
+to normal separate chaining implementations.
+
+*/
+
+#include <boost/unordered/detail/prime_fmod.hpp>
+
+#include <boost/core/addressof.hpp>
+#include <boost/core/allocator_access.hpp>
+#include <boost/core/bit.hpp>
+#include <boost/core/empty_value.hpp>
+#include <boost/core/no_exceptions_support.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/move/core.hpp>
+#include <boost/move/utility_core.hpp>
+#include <boost/swap.hpp>
+#include <boost/type_traits/aligned_storage.hpp>
+#include <boost/type_traits/alignment_of.hpp>
+
+#include <boost/config.hpp>
+
+#include <iterator>
+
+namespace boost {
+  namespace unordered {
+    namespace detail {
+
+      template <class ValueType, class VoidPtr> struct node
+      {
+        typedef ValueType value_type;
+        typedef typename boost::pointer_traits<VoidPtr>::template rebind_to<
+          node>::type node_pointer;
+
+        node_pointer next;
+        typename boost::aligned_storage<sizeof(value_type),
+          boost::alignment_of<value_type>::value>::type buf;
+
+        node() BOOST_NOEXCEPT : next(), buf() {}
+
+        value_type* value_ptr() BOOST_NOEXCEPT
+        {
+          return reinterpret_cast<value_type*>(buf.address());
+        }
+
+        value_type& value() BOOST_NOEXCEPT
+        {
+          return *reinterpret_cast<value_type*>(buf.address());
+        }
+      };
+
+      template <class Node, class VoidPtr> struct bucket
+      {
+        typedef typename boost::pointer_traits<VoidPtr>::template rebind_to<
+          Node>::type node_pointer;
+
+        typedef typename boost::pointer_traits<VoidPtr>::template rebind_to<
+          bucket>::type bucket_pointer;
+
+        node_pointer next;
+
+        bucket() BOOST_NOEXCEPT : next() {}
+      };
+
+      template <class Bucket> struct bucket_group
+      {
+        typedef typename Bucket::bucket_pointer bucket_pointer;
+        typedef
+          typename boost::pointer_traits<bucket_pointer>::template rebind_to<
+            bucket_group>::type bucket_group_pointer;
+
+        BOOST_STATIC_CONSTANT(std::size_t, N = sizeof(std::size_t) * CHAR_BIT);
+
+        bucket_pointer buckets;
+        std::size_t bitmask;
+        bucket_group_pointer next, prev;
+
+        bucket_group() BOOST_NOEXCEPT : buckets(), bitmask(0), next(), prev() {}
+        ~bucket_group() {}
+      };
+
+      inline std::size_t set_bit(std::size_t n) { return std::size_t(1) << n; }
+
+      inline std::size_t reset_bit(std::size_t n)
+      {
+        return ~(std::size_t(1) << n);
+      }
+
+      inline std::size_t reset_first_bits(std::size_t n) // n>0
+      {
+        return ~(~(std::size_t(0)) >> (sizeof(std::size_t) * 8 - n));
+      }
+
+      template <class Bucket> struct grouped_bucket_iterator
+      {
+      public:
+        typedef typename Bucket::bucket_pointer bucket_pointer;
+        typedef
+          typename boost::pointer_traits<bucket_pointer>::template rebind_to<
+            bucket_group<Bucket> >::type bucket_group_pointer;
+
+        typedef Bucket value_type;
+        typedef typename boost::pointer_traits<bucket_pointer>::difference_type
+          difference_type;
+        typedef Bucket& reference;
+        typedef Bucket* pointer;
+        typedef std::forward_iterator_tag iterator_category;
+
+      private:
+        bucket_pointer p;
+        bucket_group_pointer pbg;
+
+      public:
+        grouped_bucket_iterator() : p(), pbg() {}
+
+        reference operator*() const BOOST_NOEXCEPT { return dereference(); }
+        pointer operator->() const BOOST_NOEXCEPT
+        {
+          return boost::to_address(p);
+        }
+
+        grouped_bucket_iterator& operator++() BOOST_NOEXCEPT
+        {
+          increment();
+          return *this;
+        }
+
+        grouped_bucket_iterator operator++(int) BOOST_NOEXCEPT
+        {
+          grouped_bucket_iterator old = *this;
+          increment();
+          return old;
+        }
+
+        bool operator==(
+          grouped_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return equal(other);
+        }
+
+        bool operator!=(
+          grouped_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return !equal(other);
+        }
+
+      private:
+        template <typename, typename, typename>
+        friend class grouped_bucket_array;
+
+        BOOST_STATIC_CONSTANT(std::size_t, N = bucket_group<Bucket>::N);
+
+        grouped_bucket_iterator(bucket_pointer p_, bucket_group_pointer pbg_)
+            : p(p_), pbg(pbg_)
+        {
+        }
+
+        Bucket& dereference() const BOOST_NOEXCEPT { return *p; }
+
+        bool equal(const grouped_bucket_iterator& x) const BOOST_NOEXCEPT
+        {
+          return p == x.p;
+        }
+
+        void increment() BOOST_NOEXCEPT
+        {
+          std::size_t const offset = static_cast<std::size_t>(p - pbg->buckets);
+
+          std::size_t n = std::size_t(boost::core::countr_zero(
+            pbg->bitmask & reset_first_bits(offset + 1)));
+
+          if (n < N) {
+            p = pbg->buckets + static_cast<difference_type>(n);
+          } else {
+            pbg = pbg->next;
+
+            std::ptrdiff_t x = boost::core::countr_zero(pbg->bitmask);
+            p = pbg->buckets + x;
+          }
+        }
+      };
+
+      template <class Node> struct const_grouped_local_bucket_iterator;
+
+      template <class Node> struct grouped_local_bucket_iterator
+      {
+        typedef typename Node::node_pointer node_pointer;
+
+      public:
+        typedef typename Node::value_type value_type;
+        typedef value_type element_type;
+        typedef value_type* pointer;
+        typedef value_type& reference;
+        typedef std::ptrdiff_t difference_type;
+        typedef std::forward_iterator_tag iterator_category;
+
+        grouped_local_bucket_iterator() : p() {}
+
+        reference operator*() const BOOST_NOEXCEPT { return dereference(); }
+
+        pointer operator->() const BOOST_NOEXCEPT
+        {
+          return boost::to_address(p);
+        }
+
+        grouped_local_bucket_iterator& operator++() BOOST_NOEXCEPT
+        {
+          increment();
+          return *this;
+        }
+
+        grouped_local_bucket_iterator operator++(int) BOOST_NOEXCEPT
+        {
+          grouped_local_bucket_iterator old = *this;
+          increment();
+          return old;
+        }
+
+        bool operator==(
+          grouped_local_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return equal(other);
+        }
+
+        bool operator!=(
+          grouped_local_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return !equal(other);
+        }
+
+      private:
+        template <typename, typename, typename>
+        friend class grouped_bucket_array;
+
+        template <class> friend struct const_grouped_local_bucket_iterator;
+
+        grouped_local_bucket_iterator(node_pointer p_) : p(p_) {}
+
+        value_type& dereference() const BOOST_NOEXCEPT { return p->value(); }
+
+        bool equal(const grouped_local_bucket_iterator& x) const BOOST_NOEXCEPT
+        {
+          return p == x.p;
+        }
+
+        void increment() BOOST_NOEXCEPT { p = p->next; }
+
+        node_pointer p;
+      };
+
+      template <class Node> struct const_grouped_local_bucket_iterator
+      {
+        typedef typename Node::node_pointer node_pointer;
+
+      public:
+        typedef typename Node::value_type const value_type;
+        typedef value_type const element_type;
+        typedef value_type const* pointer;
+        typedef value_type const& reference;
+        typedef std::ptrdiff_t difference_type;
+        typedef std::forward_iterator_tag iterator_category;
+
+        const_grouped_local_bucket_iterator() : p() {}
+        const_grouped_local_bucket_iterator(
+          grouped_local_bucket_iterator<Node> it)
+            : p(it.p)
+        {
+        }
+
+        reference operator*() const BOOST_NOEXCEPT { return dereference(); }
+
+        pointer operator->() const BOOST_NOEXCEPT
+        {
+          return boost::to_address(p);
+        }
+
+        const_grouped_local_bucket_iterator& operator++() BOOST_NOEXCEPT
+        {
+          increment();
+          return *this;
+        }
+
+        const_grouped_local_bucket_iterator operator++(int) BOOST_NOEXCEPT
+        {
+          const_grouped_local_bucket_iterator old = *this;
+          increment();
+          return old;
+        }
+
+        bool operator==(
+          const_grouped_local_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return equal(other);
+        }
+
+        bool operator!=(
+          const_grouped_local_bucket_iterator const& other) const BOOST_NOEXCEPT
+        {
+          return !equal(other);
+        }
+
+      private:
+        template <typename, typename, typename>
+        friend class grouped_bucket_array;
+
+        const_grouped_local_bucket_iterator(node_pointer p_) : p(p_) {}
+
+        value_type& dereference() const BOOST_NOEXCEPT { return p->value(); }
+
+        bool equal(
+          const const_grouped_local_bucket_iterator& x) const BOOST_NOEXCEPT
+        {
+          return p == x.p;
+        }
+
+        void increment() BOOST_NOEXCEPT { p = p->next; }
+
+        node_pointer p;
+      };
+
+      template <class T> struct span
+      {
+        T* begin() const BOOST_NOEXCEPT { return data; }
+        T* end() const BOOST_NOEXCEPT { return data + size; }
+
+        T* data;
+        std::size_t size;
+
+        span(T* data_, std::size_t size_) : data(data_), size(size_) {}
+      };
+
+      template <class Bucket, class Allocator, class SizePolicy>
+      class grouped_bucket_array
+          : boost::empty_value<typename boost::allocator_rebind<Allocator,
+              node<typename boost::allocator_value_type<Allocator>::type,
+                typename boost::allocator_void_pointer<Allocator>::type> >::
+                type>
+      {
+        BOOST_MOVABLE_BUT_NOT_COPYABLE(grouped_bucket_array)
+
+        typedef typename boost::allocator_value_type<Allocator>::type
+          allocator_value_type;
+        typedef
+          typename boost::allocator_void_pointer<Allocator>::type void_pointer;
+        typedef typename boost::allocator_difference_type<Allocator>::type
+          difference_type;
+
+      public:
+        typedef typename boost::allocator_rebind<Allocator,
+          node<allocator_value_type, void_pointer> >::type node_allocator_type;
+
+        typedef node<allocator_value_type, void_pointer> node_type;
+        typedef typename boost::allocator_pointer<node_allocator_type>::type
+          node_pointer;
+        typedef SizePolicy size_policy;
+
+      private:
+        typedef typename boost::allocator_rebind<Allocator, Bucket>::type
+          bucket_allocator_type;
+        typedef typename boost::allocator_pointer<bucket_allocator_type>::type
+          bucket_pointer;
+        typedef boost::pointer_traits<bucket_pointer> bucket_pointer_traits;
+
+        typedef bucket_group<Bucket> group;
+        typedef typename boost::allocator_rebind<Allocator, group>::type
+          group_allocator_type;
+        typedef typename boost::allocator_pointer<group_allocator_type>::type
+          group_pointer;
+        typedef typename boost::pointer_traits<group_pointer>
+          group_pointer_traits;
+
+      public:
+        typedef Bucket value_type;
+        typedef Bucket bucket_type;
+        typedef std::size_t size_type;
+        typedef Allocator allocator_type;
+        typedef grouped_bucket_iterator<Bucket> iterator;
+        typedef grouped_local_bucket_iterator<node_type> local_iterator;
+        typedef const_grouped_local_bucket_iterator<node_type>
+          const_local_iterator;
+
+      private:
+        std::size_t size_index_, size_;
+        bucket_pointer buckets;
+        group_pointer groups;
+
+      public:
+        grouped_bucket_array(size_type n, const Allocator& al)
+            : empty_value<node_allocator_type>(empty_init_t(), al),
+              size_index_(size_policy::size_index(n)),
+              size_(size_policy::size(size_index_)), buckets(), groups()
+        {
+          bucket_allocator_type bucket_alloc = this->get_bucket_allocator();
+          group_allocator_type group_alloc = this->get_group_allocator();
+
+          size_type const num_buckets = buckets_len();
+          size_type const num_groups = groups_len();
+
+          buckets = boost::allocator_allocate(bucket_alloc, num_buckets);
+          BOOST_TRY
+          {
+            groups = boost::allocator_allocate(group_alloc, num_groups);
+
+            bucket_type* pb = boost::to_address(buckets);
+            for (size_type i = 0; i < num_buckets; ++i) {
+              new (pb + i) bucket_type();
+            }
+
+            group* pg = boost::to_address(groups);
+            for (size_type i = 0; i < num_groups; ++i) {
+              new (pg + i) group();
+            }
+          }
+          BOOST_CATCH(...)
+          {
+            boost::allocator_deallocate(bucket_alloc, buckets, num_buckets);
+            BOOST_RETHROW
+          }
+          BOOST_CATCH_END
+
+          size_type const N = group::N;
+          group_pointer pbg =
+            groups + static_cast<difference_type>(num_groups - 1);
+
+          pbg->buckets =
+            buckets + static_cast<difference_type>(N * (size_ / N));
+          pbg->bitmask = set_bit(size_ % N);
+          pbg->next = pbg->prev = pbg;
+        }
+
+        ~grouped_bucket_array() { this->deallocate(); }
+
+        grouped_bucket_array(
+          BOOST_RV_REF(grouped_bucket_array) other) BOOST_NOEXCEPT
+            : empty_value<node_allocator_type>(
+                empty_init_t(), other.get_node_allocator()),
+              size_index_(other.size_index_),
+              size_(other.size_),
+              buckets(other.buckets),
+              groups(other.groups)
+        {
+          other.size_ = 0;
+          other.size_index_ = 0;
+          other.buckets = bucket_pointer();
+          other.groups = group_pointer();
+        }
+
+        grouped_bucket_array& operator=(
+          BOOST_RV_REF(grouped_bucket_array) other) BOOST_NOEXCEPT
+        {
+          BOOST_ASSERT(
+            this->get_node_allocator() == other.get_node_allocator());
+
+          if (this == boost::addressof(other)) {
+            return *this;
+          }
+
+          this->deallocate();
+          size_index_ = other.size_index_;
+          size_ = other.size_;
+
+          buckets = other.buckets;
+          groups = other.groups;
+
+          other.size_index_ = 0;
+          other.size_ = 0;
+          other.buckets = bucket_pointer();
+          other.groups = group_pointer();
+
+          return *this;
+        }
+
+        void deallocate() BOOST_NOEXCEPT
+        {
+          if (buckets) {
+            bucket_allocator_type bucket_alloc = this->get_bucket_allocator();
+            boost::allocator_deallocate(
+              bucket_alloc, buckets, this->buckets_len());
+
+            buckets = bucket_pointer();
+          }
+
+          if (groups) {
+            group_allocator_type group_alloc = this->get_group_allocator();
+            boost::allocator_deallocate(
+              group_alloc, groups, this->groups_len());
+
+            groups = group_pointer();
+          }
+        }
+
+        void swap(grouped_bucket_array& other)
+        {
+          std::swap(size_index_, other.size_index_);
+          std::swap(size_, other.size_);
+          std::swap(buckets, other.buckets);
+          std::swap(groups, other.groups);
+
+          bool b = boost::allocator_propagate_on_container_swap<
+            allocator_type>::type::value;
+          if (b) {
+            boost::swap(get_node_allocator(), other.get_node_allocator());
+          }
+        }
+
+        node_allocator_type const& get_node_allocator() const
+        {
+          return empty_value<node_allocator_type>::get();
+        }
+
+        node_allocator_type& get_node_allocator()
+        {
+          return empty_value<node_allocator_type>::get();
+        }
+
+        bucket_allocator_type get_bucket_allocator() const
+        {
+          return this->get_node_allocator();
+        }
+
+        group_allocator_type get_group_allocator() const
+        {
+          return this->get_node_allocator();
+        }
+
+        size_type buckets_len() const BOOST_NOEXCEPT { return size_ + 1; }
+
+        size_type groups_len() const BOOST_NOEXCEPT
+        {
+          return size_ / group::N + 1;
+        }
+
+        void reset_allocator(Allocator const& allocator_)
+        {
+          this->get_node_allocator() = node_allocator_type(allocator_);
+        }
+
+        size_type bucket_count() const { return size_; }
+
+        iterator begin() const { return ++at(size_); }
+
+        iterator end() const
+        {
+          // micro optimization: no need to return the bucket group
+          // as end() is not incrementable
+          iterator pbg;
+          pbg.p =
+            buckets + static_cast<difference_type>(this->buckets_len() - 1);
+          return pbg;
+        }
+
+        local_iterator begin(size_type n) const
+        {
+          return local_iterator(
+            (buckets + static_cast<difference_type>(n))->next);
+        }
+
+        local_iterator end(size_type) const { return local_iterator(); }
+
+        size_type capacity() const BOOST_NOEXCEPT { return size_; }
+
+        iterator at(size_type n) const
+        {
+          std::size_t const N = group::N;
+
+          iterator pbg(buckets + static_cast<difference_type>(n),
+            groups + static_cast<difference_type>(n / N));
+
+          return pbg;
+        }
+
+        span<Bucket> raw()
+        {
+          BOOST_ASSERT(size_ == 0 || size_ < this->buckets_len());
+          return span<Bucket>(boost::to_address(buckets), size_);
+        }
+
+        size_type position(std::size_t hash) const
+        {
+          return size_policy::position(hash, size_index_);
+        }
+
+        void clear()
+        {
+          this->deallocate();
+          size_index_ = 0;
+          size_ = 0;
+        }
+
+        void append_bucket_group(iterator itb) BOOST_NOEXCEPT
+        {
+          std::size_t const N = group::N;
+
+          bool const is_empty_bucket = (!itb->next);
+          if (is_empty_bucket) {
+            bucket_pointer pb = itb.p;
+            group_pointer pbg = itb.pbg;
+
+            std::size_t n =
+              static_cast<std::size_t>(boost::to_address(pb) - &buckets[0]);
+
+            bool const is_empty_group = (!pbg->bitmask);
+            if (is_empty_group) {
+              size_type const num_groups = this->groups_len();
+              group_pointer last_group =
+                groups + static_cast<difference_type>(num_groups - 1);
+
+              pbg->buckets =
+                buckets + static_cast<difference_type>(N * (n / N));
+              pbg->next = last_group->next;
+              pbg->next->prev = pbg;
+              pbg->prev = last_group;
+              pbg->prev->next = pbg;
+            }
+
+            pbg->bitmask |= set_bit(n % N);
+          }
+        }
+
+        void insert_node(iterator itb, node_pointer p) BOOST_NOEXCEPT
+        {
+          this->append_bucket_group(itb);
+
+          p->next = itb->next;
+          itb->next = p;
+        }
+
+        void insert_node_hint(
+          iterator itb, node_pointer p, node_pointer hint) BOOST_NOEXCEPT
+        {
+          this->append_bucket_group(itb);
+
+          if (hint) {
+            p->next = hint->next;
+            hint->next = p;
+          } else {
+            p->next = itb->next;
+            itb->next = p;
+          }
+        }
+
+        void extract_node(iterator itb, node_pointer p) BOOST_NOEXCEPT
+        {
+          node_pointer* pp = boost::addressof(itb->next);
+          while ((*pp) != p)
+            pp = boost::addressof((*pp)->next);
+          *pp = p->next;
+          if (!itb->next)
+            unlink_bucket(itb);
+        }
+
+        void extract_node_after(iterator itb, node_pointer* pp) BOOST_NOEXCEPT
+        {
+          *pp = (*pp)->next;
+          if (!itb->next)
+            unlink_bucket(itb);
+        }
+
+        void unlink_empty_buckets() BOOST_NOEXCEPT
+        {
+          std::size_t const N = group::N;
+
+          group_pointer pbg = groups,
+                        last = groups + static_cast<difference_type>(
+                                          this->groups_len() - 1);
+
+          for (; pbg != last; ++pbg) {
+            if (!pbg->buckets) {
+              continue;
+            }
+
+            for (std::size_t n = 0; n < N; ++n) {
+              bucket_pointer bs = pbg->buckets;
+              bucket_type& b = bs[static_cast<std::ptrdiff_t>(n)];
+              if (!b.next)
+                pbg->bitmask &= reset_bit(n);
+            }
+            if (!pbg->bitmask && pbg->next)
+              unlink_group(pbg);
+          }
+
+          // do not check end bucket
+          for (std::size_t n = 0; n < size_ % N; ++n) {
+            if (!pbg->buckets[static_cast<std::ptrdiff_t>(n)].next)
+              pbg->bitmask &= reset_bit(n);
+          }
+        }
+
+        void unlink_bucket(iterator itb)
+        {
+          typename iterator::bucket_pointer p = itb.p;
+          typename iterator::bucket_group_pointer pbg = itb.pbg;
+          if (!(pbg->bitmask &=
+                reset_bit(static_cast<std::size_t>(p - pbg->buckets))))
+            unlink_group(pbg);
+        }
+
+      private:
+        void unlink_group(group_pointer pbg)
+        {
+          pbg->next->prev = pbg->prev;
+          pbg->prev->next = pbg->next;
+          pbg->prev = pbg->next = group_pointer();
+        }
+      };
+    } // namespace detail
+  }   // namespace unordered
+} // namespace boost
+
+#endif // BOOST_UNORDERED_DETAIL_FCA_HPP

include/boost/unordered/detail/fwd.hpp

@@ -1,5 +1,6 @@
 
 // Copyright (C) 2008-2016 Daniel James.
+// Copyright (C) 2022 Christian Mazakas
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
@@ -31,7 +32,7 @@
 // 2012 = VC+11 = BOOST_MSVC 1700 Hopefully!
 // I have no idea when Dinkumware added it, probably a lot
 // earlier than this check.
-#if BOOST_LIB_STD_DINKUMWARE >= BOOST_VERSION_NUMBER(6, 50, 0) ||              \
+#if BOOST_LIB_STD_DINKUMWARE >= BOOST_VERSION_NUMBER(6, 10, 0) ||              \
   BOOST_COMP_MSVC >= BOOST_VERSION_NUMBER(17, 0, 0)
 #define BOOST_UNORDERED_HAVE_PIECEWISE_CONSTRUCT 1
 #endif

include/boost/unordered/detail/map.hpp

@@ -1,5 +1,6 @@
 
 // Copyright (C) 2005-2016 Daniel James
+// Copyright (C) 2022 Christian Mazakas
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
@@ -25,25 +26,18 @@ namespace boost {
         typedef boost::unordered::detail::allocator_traits<value_allocator>
           value_allocator_traits;
 
-        typedef boost::unordered::detail::pick_node<A, value_type> pick;
-        typedef typename pick::node node;
-        typedef typename pick::bucket bucket;
-        typedef typename pick::link_pointer link_pointer;
-
         typedef boost::unordered::detail::table<types> table;
         typedef boost::unordered::detail::map_extractor<value_type> extractor;
 
-        typedef typename boost::unordered::detail::pick_policy<K>::type policy;
+        typedef typename boost::allocator_void_pointer<value_allocator>::type
+          void_pointer;
 
-        typedef boost::unordered::iterator_detail::iterator<node> iterator;
-        typedef boost::unordered::iterator_detail::c_iterator<node> c_iterator;
-        typedef boost::unordered::iterator_detail::l_iterator<node> l_iterator;
-        typedef boost::unordered::iterator_detail::cl_iterator<node>
-          cl_iterator;
+        typedef boost::unordered::node_handle_map<
+          node<value_type, void_pointer>, K, M, A>
+          node_type;
 
-        typedef boost::unordered::node_handle_map<node, K, M, A> node_type;
-        typedef boost::unordered::insert_return_type_map<node, K, M, A>
-          insert_return_type;
+        typedef typename table::iterator iterator;
+        typedef boost::unordered::insert_return_type_map<iterator, node_type> insert_return_type;
       };
 
       template <typename K, typename M, typename H, typename P, typename A>

include/boost/unordered/detail/prime_fmod.hpp

@@ -0,0 +1,262 @@
+// Copyright (C) 2022 Joaquin M Lopez Munoz.
+// Copyright (C) 2022 Christian Mazakas
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_UNORDERED_DETAIL_PRIME_FMOD_HPP
+#define BOOST_UNORDERED_DETAIL_PRIME_FMOD_HPP
+
+#include <boost/cstdint.hpp>
+#include <boost/preprocessor/seq/enum.hpp>
+#include <boost/preprocessor/seq/for_each.hpp>
+#include <boost/preprocessor/seq/size.hpp>
+
+#include <boost/config.hpp>
+
+#include <climits>
+#include <cstddef>
+
+#if defined(SIZE_MAX)
+#if ((((SIZE_MAX >> 16) >> 16) >> 16) >> 15) != 0
+#define BOOST_UNORDERED_FCA_HAS_64B_SIZE_T
+#endif
+#elif defined(UINTPTR_MAX) /* used as proxy for std::size_t */
+#if ((((UINTPTR_MAX >> 16) >> 16) >> 16) >> 15) != 0
+#define BOOST_UNORDERED_FCA_HAS_64B_SIZE_T
+#endif
+#endif
+
+#if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T) && defined(_MSC_VER)
+#include <intrin.h>
+#endif
+
+namespace boost {
+  namespace unordered {
+    namespace detail {
+      template <class = void> struct prime_fmod_size
+      {
+        // Because we compile for C++03, we don't have access to any inline
+        // initialization for array data members so the definitions must exist
+        // out-of-line. To keep the library header-only, we introduce a dummy
+        // template parameter which permits the definition to be included in
+        // multiple TUs without conflict.
+        //
+        static std::size_t sizes[];
+        static std::size_t const sizes_len;
+        static std::size_t (*positions[])(std::size_t);
+
+#if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+        static boost::uint64_t inv_sizes32[];
+        static std::size_t const inv_sizes32_len;
+#endif /* defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T) */
+
+        static inline std::size_t size_index(std::size_t n)
+        {
+          std::size_t i = 0;
+          for (; i < (sizes_len - 1); ++i) {
+            if (sizes[i] >= n) {
+              break;
+            }
+          }
+          return i;
+        }
+
+        static inline std::size_t size(std::size_t size_index)
+        {
+          return sizes[size_index];
+        }
+
+        template <std::size_t Size> static std::size_t modulo(std::size_t hash)
+        {
+          return hash % Size;
+        }
+
+#if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+        // We emulate the techniques taken from:
+        // Faster Remainder by Direct Computation: Applications to Compilers and
+        // Software Libraries
+        // https://arxiv.org/abs/1902.01961
+        //
+        // In essence, use fancy math to directly calculate the remainder (aka
+        // modulo) exploiting how compilers transform division
+        //
+
+        static inline boost::uint64_t get_remainder(
+          boost::uint64_t fractional, boost::uint32_t d)
+        {
+#if defined(_MSC_VER)
+          // use MSVC intrinsics when available to avoid promotion to 128 bits
+
+          return __umulh(fractional, d);
+#elif defined(BOOST_HAS_INT128)
+          return static_cast<boost::uint64_t>(
+            ((boost::uint128_type)fractional * d) >> 64);
+#else
+          // portable implementation in the absence of boost::uint128_type on 64
+          // bits, which happens at least in GCC 4.5 and prior
+
+          boost::uint64_t r1 = (fractional & UINT32_MAX) * d;
+          boost::uint64_t r2 = (fractional >> 32) * d;
+          r2 += r1 >> 32;
+          return r2 >> 32;
+#endif /* defined(_MSC_VER) */
+        }
+
+        static inline boost::uint32_t fast_modulo(
+          boost::uint32_t a, boost::uint64_t M, boost::uint32_t d)
+        {
+          boost::uint64_t fractional = M * a;
+          return (boost::uint32_t)(get_remainder(fractional, d));
+        }
+#endif /* defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T) */
+
+        static inline std::size_t position(
+          std::size_t hash, std::size_t size_index)
+        {
+#if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+          std::size_t sizes_under_32bit = inv_sizes32_len;
+          if (BOOST_LIKELY(size_index < sizes_under_32bit)) {
+            return fast_modulo(
+              boost::uint32_t(hash) + boost::uint32_t(hash >> 32),
+              inv_sizes32[size_index], boost::uint32_t(sizes[size_index]));
+          } else {
+            return positions[size_index - sizes_under_32bit](hash);
+          }
+#else
+          return positions[size_index](hash);
+#endif /* defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T) */
+        }
+      }; // prime_fmod_size
+
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT_INCOMPLETE                      \
+  (13ul)(29ul)(53ul)(97ul)(193ul)(389ul)(769ul)(1543ul)(3079ul)(6151ul)(       \
+    12289ul)(24593ul)(49157ul)(98317ul)(196613ul)(393241ul)(786433ul)(         \
+    1572869ul)(3145739ul)(6291469ul)(12582917ul)(25165843ul)(50331653ul)(      \
+    100663319ul)(201326611ul)(402653189ul)(805306457ul)(1610612741ul)(         \
+    3221225473ul)
+
+#if !defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT                                 \
+  BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT_INCOMPLETE(4294967291ul)
+
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES_64BIT
+
+#else
+
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT                                 \
+  BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT_INCOMPLETE
+
+// The original sequence here is this:
+// (6442450939ul)
+// (12884901893ul)
+// (25769803751ul)
+// (51539607551ul)
+// (103079215111ul)
+// (206158430209ul)
+// (412316860441ul)
+// (824633720831ul)
+// (1649267441651ul)
+//
+// but this causes problems on versions of mingw where the `long` type is 32
+// bits, even for 64-bit targets. We work around this by replacing the literals
+// with compile-time arithmetic, using bitshifts to reconstruct the number.
+//
+
+// clang-format off
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES_64BIT                                   \
+  ((boost::ulong_long_type(1ul) << 32)   + boost::ulong_long_type(2147483643ul)) \
+  ((boost::ulong_long_type(3ul) << 32)   + boost::ulong_long_type(5ul))          \
+  ((boost::ulong_long_type(5ul) << 32)   + boost::ulong_long_type(4294967271ul)) \
+  ((boost::ulong_long_type(11ul) << 32)  + boost::ulong_long_type(4294967295ul)) \
+  ((boost::ulong_long_type(24ul) << 32)  + boost::ulong_long_type(7ul))          \
+  ((boost::ulong_long_type(48ul) << 32)  + boost::ulong_long_type(1ul))          \
+  ((boost::ulong_long_type(96ul) << 32)  + boost::ulong_long_type(25ul))         \
+  ((boost::ulong_long_type(191ul) << 32) + boost::ulong_long_type(4294967295ul)) \
+  ((boost::ulong_long_type(383ul) << 32) + boost::ulong_long_type(4294967283ul))
+      // clang-format on
+
+#endif /* BOOST_UNORDERED_FCA_HAS_64B_SIZE_T */
+
+#define BOOST_UNORDERED_PRIME_FMOD_SIZES                                       \
+  BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT BOOST_UNORDERED_PRIME_FMOD_SIZES_64BIT
+
+      template <class T>
+      std::size_t prime_fmod_size<T>::sizes[] = {
+        BOOST_PP_SEQ_ENUM(BOOST_UNORDERED_PRIME_FMOD_SIZES)};
+
+      template <class T>
+      std::size_t const prime_fmod_size<T>::sizes_len = BOOST_PP_SEQ_SIZE(
+        BOOST_UNORDERED_PRIME_FMOD_SIZES);
+
+// Similarly here, we have to re-express the integer initialization using
+// arithmetic such that each literal can fit in a 32-bit value.
+//
+#if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+      // clang-format off
+        template <class T>
+        boost::uint64_t prime_fmod_size<T>::inv_sizes32[] = {
+          (boost::ulong_long_type(330382099ul) << 32) + boost::ulong_long_type(2973438898ul) /* = 1418980313362273202 */,
+          (boost::ulong_long_type(148102320ul) << 32) + boost::ulong_long_type(2369637129ul) /* = 636094623231363849 */,
+          (boost::ulong_long_type(81037118ul) << 32)  + boost::ulong_long_type(3403558990ul) /* = 348051774975651918 */,
+          (boost::ulong_long_type(44278013ul) << 32)  + boost::ulong_long_type(1549730468ul) /* = 190172619316593316 */,
+          (boost::ulong_long_type(22253716ul) << 32)  + boost::ulong_long_type(2403401389ul) /* = 95578984837873325 */,
+          (boost::ulong_long_type(11041047ul) << 32)  + boost::ulong_long_type(143533612ul)  /* = 47420935922132524 */,
+          (boost::ulong_long_type(5585133ul) << 32)   + boost::ulong_long_type(106117528ul)  /* = 23987963684927896 */,
+          (boost::ulong_long_type(2783517ul) << 32)   + boost::ulong_long_type(1572687312ul) /* = 11955116055547344 */,
+          (boost::ulong_long_type(1394922ul) << 32)   + boost::ulong_long_type(3428720239ul) /* = 5991147799191151 */,
+          (boost::ulong_long_type(698255ul) << 32)    + boost::ulong_long_type(552319807ul)  /* = 2998982941588287 */,
+          (boost::ulong_long_type(349496ul) << 32)    + boost::ulong_long_type(3827689953ul) /* = 1501077717772769 */,
+          (boost::ulong_long_type(174641ul) << 32)    + boost::ulong_long_type(3699438549ul) /* = 750081082979285 */,
+          (boost::ulong_long_type(87372ul) << 32)     + boost::ulong_long_type(1912757574ul) /* = 375261795343686 */,
+          (boost::ulong_long_type(43684ul) << 32)     + boost::ulong_long_type(3821029929ul) /* = 187625172388393 */,
+          (boost::ulong_long_type(21844ul) << 32)     + boost::ulong_long_type(3340590800ul) /* = 93822606204624 */,
+          (boost::ulong_long_type(10921ul) << 32)     + boost::ulong_long_type(4175852267ul) /* = 46909513691883 */,
+          (boost::ulong_long_type(5461ul) << 32)      + boost::ulong_long_type(1401829642ul) /* = 23456218233098 */,
+          (boost::ulong_long_type(2730ul) << 32)      + boost::ulong_long_type(2826028947ul) /* = 11728086747027 */,
+          (boost::ulong_long_type(1365ul) << 32)      + boost::ulong_long_type(1411150351ul) /* = 5864041509391 */,
+          (boost::ulong_long_type(682ul) << 32)       + boost::ulong_long_type(2857253105ul) /* = 2932024948977 */,
+          (boost::ulong_long_type(341ul) << 32)       + boost::ulong_long_type(1431073224ul) /* = 1466014921160 */,
+          (boost::ulong_long_type(170ul) << 32)       + boost::ulong_long_type(2862758116ul) /* = 733007198436 */,
+          (boost::ulong_long_type(85ul) << 32)        + boost::ulong_long_type(1431619357ul) /* = 366503839517 */,
+          (boost::ulong_long_type(42ul) << 32)        + boost::ulong_long_type(2863269661ul) /* = 183251896093 */,
+          (boost::ulong_long_type(21ul) << 32)        + boost::ulong_long_type(1431647119ul) /* = 91625960335 */,
+          (boost::ulong_long_type(10ul) << 32)        + boost::ulong_long_type(2863310962ul) /* = 45812983922 */,
+          (boost::ulong_long_type(5ul) << 32)         + boost::ulong_long_type(1431653234ul) /* = 22906489714 */,
+          (boost::ulong_long_type(2ul) << 32)         + boost::ulong_long_type(2863311496ul) /* = 11453246088 */,
+          (boost::ulong_long_type(1ul) << 32)         + boost::ulong_long_type(1431655764ul) /* = 5726623060 */,
+        };
+      // clang-format on
+
+      template <class T>
+      std::size_t const
+        prime_fmod_size<T>::inv_sizes32_len = sizeof(inv_sizes32) /
+                                              sizeof(inv_sizes32[0]);
+
+#endif /* defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T) */
+
+#define BOOST_UNORDERED_PRIME_FMOD_POSITIONS_ELEMENT(z, _, n)                  \
+  prime_fmod_size<T>::template modulo<n>,
+
+      template <class T>
+      std::size_t (*prime_fmod_size<T>::positions[])(std::size_t) = {
+#if !defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
+        BOOST_PP_SEQ_FOR_EACH(BOOST_UNORDERED_PRIME_FMOD_POSITIONS_ELEMENT, ~,
+          BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT)
+#else
+        BOOST_PP_SEQ_FOR_EACH(BOOST_UNORDERED_PRIME_FMOD_POSITIONS_ELEMENT, ~,
+          BOOST_UNORDERED_PRIME_FMOD_SIZES_64BIT)
+#endif
+      };
+
+#undef BOOST_UNORDERED_PRIME_FMOD_POSITIONS_ELEMENT
+#undef BOOST_UNORDERED_PRIME_FMOD_SIZES
+#undef BOOST_UNORDERED_PRIME_FMOD_SIZES_64BIT
+#undef BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT
+#undef BOOST_UNORDERED_PRIME_FMOD_SIZES_32BIT_INCOMPLETE
+    } // namespace detail
+  }   // namespace unordered
+} // namespace boost
+
+#endif // BOOST_UNORDERED_DETAIL_PRIME_FMOD_HPP