Avoid shadowing wanrings from DateTime

Feature/proxy erase

.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 +8,207 @@ 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 2013
-      TOOLSET: msvc-10.0,msvc-11.0,msvc-12.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      TOOLSET: msvc-14.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc-14.1
+    - 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, C++14
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      B2_CXXSTD: 14
+      B2_TOOLSET: msvc-14.1
+
+    - FLAVOR: Visual Studio 2017, C++17
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      B2_CXXSTD: 17
+      B2_TOOLSET: msvc-14.1
+
+    - FLAVOR: Visual Studio 2017, C++latest
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      B2_CXXSTD: latest
+      B2_TOOLSET: msvc-14.1
+
+    - FLAVOR: cygwin (32-bit, C++03,11)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin\bin;
+      B2_ADDRESS_MODEL: 32
+      B2_CXXSTD: 03,11
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (32-bit, C++14,1z)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin\bin;
+      B2_ADDRESS_MODEL: 32
+      B2_CXXSTD: 14,1z
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (64-bit, C++03,11)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 03,11
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (64-bit, C++14,1z)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 14,1z
+      B2_TOOLSET: gcc
+
+    - FLAVOR: cygwin (64-bit, latest, C++03)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 03
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+      B2_VARIANT: release
+
+    - FLAVOR: cygwin (64-bit, latest, C++11)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 11
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+      B2_VARIANT: release
+
+    - FLAVOR: cygwin (64-bit, latest, C++14)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 14
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+      B2_VARIANT: release
+
+    - FLAVOR: cygwin (64-bit, latest, C++1z)
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+      ADDPATH: C:\cygwin64\bin;
+      B2_ADDRESS_MODEL: 64
+      B2_CXXSTD: 1z
+      B2_TOOLSET: gcc
+      B2_FLAGS: "include=libs/unordered/test/unordered include=libs/unordered/test/exception"
+      B2_VARIANT: release
+
+    - FLAVOR: mingw-w64, 32 bit, C++03
+      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
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 32 bit, C++11
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin;
+      B2_CXXSTD: 11
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 32 bit, C++14
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin;
+      B2_CXXSTD: 14
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 32 bit, C++17
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin;
+      B2_CXXSTD: 17
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 32 bit, C++2a
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      ADDPATH: C:\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\bin;
+      B2_CXXSTD: 2a
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 32
+
+    - FLAVOR: mingw-w64, 64 bit, C++03
+      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
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 64
+
+    - FLAVOR: mingw-w64, 64 bit, C++11
+      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: 11
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 64
+
+    - FLAVOR: mingw-w64, 64 bit, C++14
+      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: 14
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 64
+
+    - FLAVOR: mingw-w64, 64 bit, C++17
+      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: 17
+      B2_TOOLSET: gcc
+      B2_ADDRESS_MODEL: 64
+
+    - FLAVOR: mingw-w64, 64 bit, C++2a
+      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: 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 +1,515 @@
+# 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/*", "fix/*", "pr/*" ]
+};
+
+local ubsan = { UBSAN: '1', UBSAN_OPTIONS: 'print_stacktrace=1' };
+local asan = { ASAN: '1' };
+local tsan = { TSAN: '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',
+                'uname -a',
+                '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:
+            [
+                'uname -a',
+                '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:
+            [
+                'echo $env:DRONE_STAGE_MACHINE',
+                '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 16.04 GCC 5* 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 6 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-6', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+        "g++-6-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 7* 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 8 32/64 (03,11)",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-8', CXXSTD: '03,11', ADDRMD: '32,64' },
+        "g++-8-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 8 32/64 (14,17)",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-8', CXXSTD: '14,17', ADDRMD: '32,64' },
+        "g++-8-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 32/64 (03,11,14)",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 32/64 (17,2a)",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '17,2a', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* ARM64",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a' },
+        arch="arm64",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* S390x (03,11,14)",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14' },
+        arch="s390x",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* S390x (17,2a)",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '17,2a' },
+        arch="s390x",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32/64 (03,11,14)",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32/64 (17,20)",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '17,20', ADDRMD: '32,64' },
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 32/64 (03,11,14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 32/64 (17,2a)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '17,2a', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN (03,11,14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN (14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '14', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN (17)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '17', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN (20)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '20', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN (2b)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '2b', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 ASAN (03,11,14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14', ADDRMD: '64' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 ASAN (17)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '17', ADDRMD: '64' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 ASAN (20)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '20', ADDRMD: '64' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 ASAN (2b)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '2b', ADDRMD: '64' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 TSAN (11,14,17,20,2b)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '11,14,17,20,2b', ADDRMD: '64', TARGET: 'libs/unordered/test//cfoa_tests' } + tsan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 32/64 (03,11,14)",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+        "g++-13 g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 32/64 (17,20,2b)",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '17,20,2b', ADDRMD: '32,64' },
+        "g++-13 g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.5",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.5', CXXSTD: '03,11' },
+        "clang-3.5",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.6",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.6', CXXSTD: '03,11,14' },
+        "clang-3.6",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.7",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.7', CXXSTD: '03,11,14' },
+        "clang-3.7",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.8",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.8', CXXSTD: '03,11,14' },
+        "clang-3.8",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 3.9",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.9', CXXSTD: '03,11,14' },
+        "clang-3.9",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 4.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-4.0', CXXSTD: '03,11,14' },
+        "clang-4.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 5.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-5.0', CXXSTD: '03,11,14,1z' },
+        "clang-5.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 6.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-6.0', CXXSTD: '03,11,14,17' },
+        "clang-6.0",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 7",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-7', CXXSTD: '03,11,14,17' },
+        "clang-7",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 8",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-8', CXXSTD: '03,11,14,17' },
+        "clang-8",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 9",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-9', CXXSTD: '03,11,14,17,2a' },
+        "clang-9",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 10",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-10', CXXSTD: '03,11,14,17,2a' },
+        "clang-10",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 11",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-11', CXXSTD: '03,11,14,17,2a' },
+        "clang-11",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 12",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-12', CXXSTD: '03,11,14,17,2a' },
+        "clang-12",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 13",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-13', CXXSTD: '03,11,14,17,20' },
+        "clang-13",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14 UBSAN (03,11,14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14' } + ubsan,
+        "clang-14",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14 UBSAN (17,20)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '17,20' } + ubsan,
+        "clang-14",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14 ASAN (03,11,14)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14' } + asan,
+        "clang-14",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14 ASAN (17,20)",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '17,20' } + asan,
+        "clang-14",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14 libc++ 64 TSAN",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', ADDRMD: '64', TARGET: 'libs/unordered/test//cfoa_tests', CXXSTD: '11,14,17,20', STDLIB: 'libc++' } + tsan,
+        "clang-14 libc++-14-dev libc++abi-14-dev",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 15",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' },
+        "clang-15",
+        ["deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main"],
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN (03,11)",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN (14)",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '14' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN (1z)",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '1z' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 12.4 Xcode 13.4.1 ASAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + asan,
+        xcode_version = "13.4.1", osx_version = "monterey", arch = "arm64",
+    ),
+
+    macos_pipeline(
+        "MacOS 12.4 Xcode 13.4.1 TSAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,1z', TARGET: 'libs/unordered/test//cfoa_tests' } + tsan,
+        xcode_version = "13.4.1", osx_version = "monterey", arch = "arm64",
+    ),
+
+    windows_pipeline(
+        "Windows VS2015 msvc-14.0",
+        "cppalliance/dronevs2015",
+        { TOOLSET: 'msvc-14.0', CXXSTD: '14,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2017 msvc-14.1",
+        "cppalliance/dronevs2017",
+        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2019 msvc-14.2",
+        "cppalliance/dronevs2019",
+        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17,20,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2022 msvc-14.3",
+        "cppalliance/dronevs2022:1",
+        { TOOLSET: 'msvc-14.3', CXXSTD: '14,17,20,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 +1,27 @@
+#!/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
+export PATH=~/.local/bin:/usr/local/bin:$PATH
+
+: ${TARGET:="libs/$LIBRARY/test"}
+
+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 $TARGET toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${ADDRMD:+address-model=$ADDRMD} ${STDLIB:+stdlib=$STDLIB} ${UBSAN:+undefined-sanitizer=norecover debug-symbols=on} ${ASAN:+address-sanitizer=norecover debug-symbols=on} ${TSAN:+thread-sanitizer=norecover debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}

.github/workflows/ci.yml

@@ -0,0 +1,406 @@
+# 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-7,     cxxstd: '03,11,14,17',    os: ubuntu-20.04, install: 'g++-7' }
+          - { compiler: gcc-8,     cxxstd: '03,11,14,17',    os: ubuntu-20.04, install: 'g++-8' }
+          - { compiler: gcc-9,     cxxstd: '03,11,14,17',    os: ubuntu-20.04, install: 'g++-9' }
+          - { compiler: gcc-10,    cxxstd: '03,11,14,17,20', os: ubuntu-22.04, install: 'g++-10' }
+          - { compiler: gcc-11,    cxxstd: '03,11,14,17,20', os: ubuntu-22.04, install: 'g++-11' }
+          - { name: "gcc-12 w/ sanitizers (03,11,14)", sanitize: yes,
+              compiler: gcc-12,    cxxstd: '03,11,14',       os: ubuntu-22.04, ccache_key: "san1" }
+          - { name: "gcc-12 w/ sanitizers (17,20,2b)", sanitize: yes,
+              compiler: gcc-12,    cxxstd: '17,20,2b',       os: ubuntu-22.04, ccache_key: "san2" }
+          - { name: Collect coverage, coverage: yes,
+              compiler: gcc-12,     cxxstd: '03,20',          os: ubuntu-22.04, install: 'g++-12-multilib', address-model: '32,64', ccache_key: "cov" }
+
+          - { name: "cfoa tsan (gcc)", cxxstd: '11,14,17,20,2b', os: ubuntu-22.04, compiler: gcc-12,
+              targets: 'libs/unordered/test//cfoa_tests', thread-sanitize: yes }
+
+          # Linux, clang, libc++
+          - { compiler: clang-7,   cxxstd: '03,11,14,17',       os: ubuntu-20.04, stdlib: libc++, install: 'clang-7 libc++-7-dev libc++abi-7-dev' }
+          - { compiler: clang-10,  cxxstd: '03,11,14,17,20',    os: ubuntu-20.04, stdlib: libc++, install: 'clang-10 libc++-10-dev libc++abi-10-dev' }
+          - { compiler: clang-11,  cxxstd: '03,11,14,17,20',    os: ubuntu-22.04, stdlib: libc++, install: 'clang-11 libc++-11-dev libc++abi-11-dev' }
+          # clang-12 doesn't work on ubuntu-22.04, the linker can't find -lunwind for some reason
+          - { name: "clang-12 w/ sanitizers (03,11,14)", sanitize: yes,
+              compiler: clang-12,  cxxstd: '03,11,14',          os: ubuntu-20.04, stdlib: libc++, install: 'clang-12 libc++-12-dev libc++abi-12-dev', ccache_key: "san1" }
+          - { name: "clang-12 w/ sanitizers (17,20,2b)", sanitize: yes,
+              compiler: clang-12,  cxxstd: '17,20,2b',          os: ubuntu-20.04, stdlib: libc++, install: 'clang-12 libc++-12-dev libc++abi-12-dev', ccache_key: "san2" }
+          - { compiler: clang-13,  cxxstd: '03,11,14,17,20,2b', os: ubuntu-22.04, stdlib: libc++, install: 'clang-13 libc++-13-dev libc++abi-13-dev' }
+          - { compiler: clang-14,  cxxstd: '03,11,14,17,20,2b', os: ubuntu-22.04, stdlib: libc++, install: 'clang-14 libc++-14-dev libc++abi-14-dev' }
+
+          # not using libc++ because of https://github.com/llvm/llvm-project/issues/52771
+          - { name: "clang-14 w/ sanitizers (03,11,14)", sanitize: yes,
+              compiler: clang-14,  cxxstd: '03,11,14',          os: ubuntu-22.04, ccache_key: "san1" }
+          - { name: "clang-14 w/ sanitizers (17,20,2b)", sanitize: yes,
+              compiler: clang-14,  cxxstd: '17,20,2b',          os: ubuntu-22.04, ccache_key: "san2" }
+
+          - { name: "cfoa tsan (clang)", cxxstd: '11,14,17,20,2b', os: ubuntu-22.04, compiler: clang-14,
+              targets: 'libs/unordered/test//cfoa_tests', thread-sanitize: yes, 
+              stdlib: libc++, install: 'clang-14 libc++-14-dev libc++abi-14-dev' }
+
+          # OSX, clang
+          - { compiler: clang,     cxxstd: '03,11,14,17,2a',    os: macos-11, }
+          - { compiler: clang,     cxxstd: '03,11,14,17,2a',    os: macos-12, sanitize: yes }
+          - { compiler: clang,     cxxstd: '11,14,17,2a',       os: macos-12, thread-sanitize: yes, targets: 'libs/unordered/test//cfoa_tests' }
+
+    timeout-minutes: 180
+    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}}-${{matrix.compiler}}-${{matrix.ccache_key}}-${{github.sha}}
+          restore-keys: ${{matrix.os}}-${{matrix.container}}-${{matrix.compiler}}-${{matrix.ccache_key}}-
+
+      - 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_TSAN: ${{matrix.thread-sanitize}}
+          B2_TARGETS: ${{matrix.targets}}
+          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: ${{matrix.variant}}
+        run: source ci/github/install.sh
+
+      - name: Setup coverage collection
+        if: matrix.coverage
+        run: ci/github/codecov.sh "setup"
+
+      - name: Run tests
+        if: '!matrix.coverity'
+        run: B2_TARGETS=${{matrix.targets}} 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, variant: 'debug,release' }
+          - { toolset: msvc-14.2, cxxstd: '14,17,20,latest', addrmd: '32,64', os: windows-2019, variant: 'debug,release' }
+          - { toolset: msvc-14.3, cxxstd: '14,17,20,latest', addrmd: '32,64', os: windows-2022, variant: 'debug,release' }
+          - { toolset: msvc-14.3, cxxstd: '14',              addrmd: '64',    os: windows-2022, variant: 'debug', defines: '_ALLOW_RTCc_IN_STL', cxxflags: '/RTCc'              }
+          - { toolset: msvc-14.3, cxxstd: '14',              addrmd: '32',    os: windows-2022, variant: 'debug', defines: '_ALLOW_RTCc_IN_STL', cxxflags: '"/RTCc /arch:IA32"' }
+          - { toolset: clang-win, cxxstd: '14,17,latest',    addrmd: '32,64', os: windows-2022, variant: 'debug,release' }
+          - { toolset: gcc,       cxxstd: '03,11,14,17,2a',  addrmd: '64',    os: windows-2019, variant: 'debug,release' }
+
+    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}}
+          B2_DEFINES: ${{matrix.defines}}
+          B2_VARIANT: ${{matrix.variant}}
+          B2_CXXFLAGS: ${{matrix.cxxflags}}
+
+      - 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}}

.gitignore

@@ -1 +1,2 @@
 /doc/html/
+/doc/pdf/

CMakeLists.txt

@@ -0,0 +1,35 @@
+# Generated by `boostdep --cmake unordered`
+# 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...3.20)
+
+project(boost_unordered VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
+
+add_library(boost_unordered INTERFACE)
+add_library(Boost::unordered ALIAS boost_unordered)
+
+target_include_directories(boost_unordered INTERFACE include)
+
+target_link_libraries(boost_unordered
+  INTERFACE
+    Boost::assert
+    Boost::config
+    Boost::container_hash
+    Boost::core
+    Boost::move
+    Boost::mp11
+    Boost::predef
+    Boost::preprocessor
+    Boost::static_assert
+    Boost::throw_exception
+    Boost::tuple
+    Boost::type_traits
+)
+
+if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
+
+  add_subdirectory(test)
+
+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/.gitignore

@@ -0,0 +1,3 @@
+enwik8
+enwik9
+*.exe

benchmark/string.cpp

@@ -0,0 +1,431 @@
+// Copyright 2021 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.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_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::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 >
+{
+    using is_avalanching = void;
+};
+
+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 boost_unordered_node_map_fnv1a =
+    boost::unordered_node_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map_fnv1a =
+    boost::unordered_flat_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map_fnv1a =
+    ankerl::unordered_dense::map<K, V, fnv1a_hash, 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<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    test<std_unordered_map_fnv1a>( "std::unordered_map, FNV-1a" );
+    test<boost_unordered_map_fnv1a>( "boost::unordered_map, FNV-1a" );
+    test<boost_unordered_node_map_fnv1a>( "boost::unordered_node_map, FNV-1a" );
+    test<boost_unordered_flat_map_fnv1a>( "boost::unordered_flat_map, FNV-1a" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map_fnv1a>( "ankerl::unordered_dense::map, FNV-1a" );
+
+#endif
+
+#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
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 38 ) << ( 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 +1,432 @@
+// Copyright 2021 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.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_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::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 >
+{
+    using is_avalanching = void;
+};
+
+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 boost_unordered_node_map_fnv1a =
+    boost::unordered_node_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map_fnv1a =
+    boost::unordered_flat_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map_fnv1a =
+    ankerl::unordered_dense::map<K, V, fnv1a_hash, 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<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    test<std_unordered_map_fnv1a>( "std::unordered_map, FNV-1a" );
+    test<boost_unordered_map_fnv1a>( "boost::unordered_map, FNV-1a" );
+    test<boost_unordered_node_map_fnv1a>( "boost::unordered_node_map, FNV-1a" );
+    test<boost_unordered_flat_map_fnv1a>( "boost::unordered_flat_map, FNV-1a" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map_fnv1a>( "ankerl::unordered_dense::map, FNV-1a" );
+
+#endif
+
+#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
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 38 ) << ( 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 +1,352 @@
+// Copyright 2021 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.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_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::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<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 30 ) << ( 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 +1,362 @@
+// Copyright 2021 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.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_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+int main()
+{
+    init_indices();
+
+#if defined(BOOST_LIBSTDCXX_VERSION) && __SIZE_WIDTH__ == 32
+
+    // Pathological behavior:
+    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104945
+
+#else
+
+    test<std_unordered_map>( "std::unordered_map" );
+
+#endif
+
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 30 ) << ( 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/uuid.cpp

@@ -0,0 +1,403 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.hpp>
+#include <boost/endian/conversion.hpp>
+#include <boost/core/detail/splitmix64.hpp>
+#include <boost/container_hash/hash.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_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+#include <cstring>
+
+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;
+
+struct uuid
+{
+    unsigned char data[ 16 ];
+
+    uuid(): data()
+    {
+    }
+
+    uuid( std::uint64_t low, std::uint64_t high ) noexcept
+    {
+        boost::endian::store_little_u64( data + 0, low );
+        boost::endian::store_little_u64( data + 8, high );
+    }
+
+    inline friend std::size_t hash_value( uuid const& u ) noexcept
+    {
+        std::uint64_t low  = boost::endian::load_little_u64( u.data + 0 );
+        std::uint64_t high = boost::endian::load_little_u64( u.data + 8 );
+
+        std::size_t r = 0;
+
+        boost::hash_combine( r, low );
+        boost::hash_combine( r, high );
+
+        return r;
+    }
+
+    inline friend bool operator==( uuid const& u1, uuid const& u2 ) noexcept
+    {
+        return std::memcmp( u1.data, u2.data, 16 ) == 0;
+    }
+};
+
+namespace std
+{
+
+template<> struct hash< ::uuid >
+{
+    std::size_t operator()( uuid const& u ) const noexcept
+    {
+        return hash_value( u );
+    }
+};
+
+} // namespace std
+
+static std::vector< uuid > indices1, indices2, indices3;
+
+static void init_indices()
+{
+    indices1.push_back( {} );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        indices1.push_back( { i, 0 } );
+    }
+
+    indices2.push_back( {} );
+
+    {
+        boost::detail::splitmix64 rng;
+
+        for( unsigned i = 1; i <= N*2; ++i )
+        {
+            indices2.push_back( { rng(), rng() } );
+        }
+    }
+
+    indices3.push_back( {} );
+
+    for( unsigned i = 1; i <= N*2; ++i )
+    {
+        uuid k( i, 0 );
+        std::reverse( k.data + 0, k.data + 16 );
+
+        indices3.push_back( k );
+    }
+}
+
+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<uuid, 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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::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<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 30 ) << ( 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/word_count.cpp

@@ -0,0 +1,386 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.hpp>
+#include <boost/regex.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+#include <fstream>
+#include <string_view>
+#include <string>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::size_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;
+}
+
+static std::vector<std::string> words;
+
+static void init_words()
+{
+#if SIZE_MAX > UINT32_MAX
+
+    char const* fn = "enwik9"; // http://mattmahoney.net/dc/textdata
+
+#else
+
+    char const* fn = "enwik8"; // ditto
+
+#endif
+
+    auto t1 = std::chrono::steady_clock::now();
+
+    std::ifstream is( fn );
+    std::string in( std::istreambuf_iterator<char>( is ), std::istreambuf_iterator<char>{} );
+
+    boost::regex re( "[a-zA-Z]+");
+    boost::sregex_token_iterator it( in.begin(), in.end(), re, 0 ), end;
+
+    words.assign( it, end );
+
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << fn << ": " << words.size() << " words, " << ( t2 - t1 ) / 1ms << " ms\n\n";
+}
+
+template<class Map> BOOST_NOINLINE void test_word_count( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::size_t s = 0;
+
+    for( auto const& word: words )
+    {
+        ++map[ word ];
+        ++s;
+    }
+
+    print_time( t1, "Word count", s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_contains( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::size_t s = 0;
+
+    for( auto const& word: words )
+    {
+        std::string_view w2( word );
+        w2.remove_prefix( 1 );
+
+        s += map.contains( w2 );
+    }
+
+    print_time( t1, "Contains", s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_count( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::size_t s = 0;
+
+    for( auto const& word: words )
+    {
+        std::string_view w2( word );
+        w2.remove_prefix( 1 );
+
+        s += map.count( w2 );
+    }
+
+    print_time( t1, "Count", s, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::size_t max = 0;
+    std::string_view word;
+
+    for( auto const& x: map )
+    {
+        if( x.second > max )
+        {
+            word = x.first;
+            max = x.second;
+        }
+    }
+
+    print_time( t1, "Iterate and find max element",  max, 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::size_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_word_count( 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_contains( map, t1 );
+    test_count( map, t1 );
+    test_iteration( 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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::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 >
+{
+    using is_avalanching = void;
+};
+
+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 boost_unordered_node_map_fnv1a =
+    boost::unordered_node_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map_fnv1a =
+    boost::unordered_flat_map<K, V, fnv1a_hash, std::equal_to<K>, allocator_for<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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map_fnv1a =
+    ankerl::unordered_dense::map<K, V, fnv1a_hash, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+//
+
+int main()
+{
+    init_words();
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    test<std_unordered_map_fnv1a>( "std::unordered_map, FNV-1a" );
+    test<boost_unordered_map_fnv1a>( "boost::unordered_map, FNV-1a" );
+    test<boost_unordered_node_map_fnv1a>( "boost::unordered_node_map, FNV-1a" );
+    test<boost_unordered_flat_map_fnv1a>( "boost::unordered_flat_map, FNV-1a" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map_fnv1a>( "ankerl::unordered_dense::map, FNV-1a" );
+
+#endif
+
+#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
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 38 ) << ( 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/word_size.cpp

@@ -0,0 +1,244 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Copyright 2023 Joaquin M Lopez Munoz.
+// 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
+#define _SILENCE_CXX20_CISO646_REMOVED_WARNING
+
+#include <boost/unordered_map.hpp>
+#include <boost/unordered/unordered_node_map.hpp>
+#include <boost/unordered/unordered_flat_map.hpp>
+#include <boost/regex.hpp>
+#ifdef HAVE_ABSEIL
+# include "absl/container/node_hash_map.h"
+# include "absl/container/flat_hash_map.h"
+#endif
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+# include "ankerl/unordered_dense.h"
+#endif
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <cstdint>
+#include <iostream>
+#include <iomanip>
+#include <chrono>
+#include <fstream>
+
+using namespace std::chrono_literals;
+
+static void print_time( std::chrono::steady_clock::time_point & t1, char const* label, std::size_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;
+}
+
+static std::vector<std::string> words;
+
+static void init_words()
+{
+#if SIZE_MAX > UINT32_MAX
+
+    char const* fn = "enwik9"; // http://mattmahoney.net/dc/textdata
+
+#else
+
+    char const* fn = "enwik8"; // ditto
+
+#endif
+
+    auto t1 = std::chrono::steady_clock::now();
+
+    std::ifstream is( fn );
+    std::string in( std::istreambuf_iterator<char>( is ), std::istreambuf_iterator<char>{} );
+
+    boost::regex re( "[a-zA-Z]+");
+    boost::sregex_token_iterator it( in.begin(), in.end(), re, 0 ), end;
+
+    words.assign( it, end );
+
+    auto t2 = std::chrono::steady_clock::now();
+
+    std::cout << fn << ": " << words.size() << " words, " << ( t2 - t1 ) / 1ms << " ms\n\n";
+}
+
+template<class Map> BOOST_NOINLINE void test_word_size( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    for( auto const& word: words )
+    {
+        ++map[ word.size() ];
+    }
+
+    print_time( t1, "Word size count",  0, map.size() );
+
+    std::cout << std::endl;
+}
+
+template<class Map> BOOST_NOINLINE void test_iteration( Map& map, std::chrono::steady_clock::time_point & t1 )
+{
+    std::size_t s = 0;
+
+    for( auto const& x: map )
+    {
+        s += x.second;
+    }
+
+    print_time( t1, "Iterate and sum counts",  s, 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::size_t, std::size_t> map;
+
+    auto t0 = std::chrono::steady_clock::now();
+    auto t1 = t0;
+
+    test_word_size( 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_iteration( 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 );
+}
+
+// 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>>;
+
+template<class K, class V> using boost_unordered_node_map =
+    boost::unordered_node_map<K, V, boost::hash<K>, std::equal_to<K>, allocator_for<K, V>>;
+
+template<class K, class V> using boost_unordered_flat_map =
+    boost::unordered_flat_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_ANKERL_UNORDERED_DENSE
+
+template<class K, class V> using ankerl_unordered_dense_map =
+    ankerl::unordered_dense::map<K, V, ankerl::unordered_dense::hash<K>, std::equal_to<K>, ::allocator< std::pair<K, V> >>;
+
+#endif
+
+int main()
+{
+    init_words();
+
+    test<std_unordered_map>( "std::unordered_map" );
+    test<boost_unordered_map>( "boost::unordered_map" );
+    test<boost_unordered_node_map>( "boost::unordered_node_map" );
+    test<boost_unordered_flat_map>( "boost::unordered_flat_map" );
+
+#ifdef HAVE_ANKERL_UNORDERED_DENSE
+
+    test<ankerl_unordered_dense_map>( "ankerl::unordered_dense::map" );
+
+#endif
+
+#ifdef HAVE_ABSEIL
+
+    test<absl_node_hash_map>( "absl::node_hash_map" );
+    test<absl_flat_hash_map>( "absl::flat_hash_map" );
+
+#endif
+
+    std::cout << "---\n\n";
+
+    for( auto const& x: times )
+    {
+        std::cout << std::setw( 30 ) << ( 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]

doc/compliance.qbk

@@ -1,128 +0,0 @@
-[/ 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) ]
-
-[section:compliance Standard Compliance]
-
-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.
-The wide compatibility does mean some comprimises have to be made.
-With a compiler and library that fully support C++11, the differences should
-be minor.
-
-[section:move 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,
-but imperfect emulation. On such compilers:
-
-* Non-copyable objects can be stored in the containers.
-  They can be constructed in place using `emplace`, or if they support
-  Boost.Move, moved into place.
-* The containers themselves are not movable.
-* Argument forwarding is not perfect.
-
-[endsect]
-
-[section:allocator_compliance Use of allocators]
-
-C++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.
-It uses a traits class, `allocator_traits` to handle the allocator
-adding extra functionality, and making some methods and types optional.
-During development a stable release of
-`allocator_traits` wasn't available so an internal partial implementation
-is always used in this version. Hopefully a future version will use the
-standard implementation where available.
-
-The member functions `construct`, `destroy` and `max_size` are now
-optional, if they're not available a fallback is used.
-A full implementation of `allocator_traits` requires sophisticated
-member function detection so that the fallback is used whenever the
-member function call is not well formed.
-This requires support for SFINAE expressions, which are available on
-GCC from version 4.4 and Clang.
-
-On other compilers, there's just a test to see if the allocator has
-a member, but no check that it can be called. So rather than using a
-fallback there will just be a compile error.
-
-`propagate_on_container_copy_assignment`,
-`propagate_on_container_move_assignment`,
-`propagate_on_container_swap` and
-`select_on_container_copy_construction` are also supported.
-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]
-
-[section:construction Construction/Destruction using allocators]
-
-The following support is required for full use of C++11 style
-construction/destruction:
-
-* Variadic templates.
-* Piecewise construction of `std::pair`.
-* Either `std::allocator_traits` or expression SFINAE.
-
-This is detected using Boost.Config. The macro
-`BOOST_UNORDERED_CXX11_CONSTRUCTION` will be set to 1 if it is found, or 0
-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.
-
-When support is not available `allocator_traits::construct` and
-`allocator_traits::destroy` are never called.
-
-[endsect]
-
-[section: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
-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]
-
-Since the containers use `std::pair` they're limited to the version
-from the current standard library. But since C++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;
-
-    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]
-
-When swapping, `Pred` and `Hash` are not currently swapped by calling
-`swap`, their copy constructors are used. As a consequence when swapping
-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]