From 2fae05ed316a81e9d6b795367106cfaa410b7419 Mon Sep 17 00:00:00 2001
From: joaquintides <joaquin@tid.es>
Date: Sun, 19 Mar 2023 13:08:29 +0100
Subject: [PATCH] made concurrent_table use table_core's automatic capacity
 growth formula

---
 .../unordered/detail/foa/concurrent_table.hpp |  4 +--
 include/boost/unordered/detail/foa/core.hpp   | 35 ++++++++++++-------
 2 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/include/boost/unordered/detail/foa/concurrent_table.hpp b/include/boost/unordered/detail/foa/concurrent_table.hpp
index c010997f..c33f594d 100644
--- a/include/boost/unordered/detail/foa/concurrent_table.hpp
+++ b/include/boost/unordered/detail/foa/concurrent_table.hpp
@@ -621,7 +621,6 @@ private:
   using group_insert_counter_type=typename group_access::insert_counter_type;
 #endif
 
-
   concurrent_table(const concurrent_table& x,exclusive_lock_guard):
     super{x}{}
   concurrent_table(concurrent_table&& x,exclusive_lock_guard):
@@ -901,8 +900,7 @@ private:
   void rehash_if_full()
   {
     auto lck=exclusive_access();
-    // TODO: use same mechanism as unchecked_emplace_with_rehash
-    if(this->size_==this->ml)super::rehash(super::capacity()+1);
+    if(this->size_==this->ml)this->unchecked_rehash_for_growth();
   }
 
 #if defined(BOOST_UNORDERED_PARALLEL_ALGORITHMS)
diff --git a/include/boost/unordered/detail/foa/core.hpp b/include/boost/unordered/detail/foa/core.hpp
index 6d7e8df4..feefe33c 100644
--- a/include/boost/unordered/detail/foa/core.hpp
+++ b/include/boost/unordered/detail/foa/core.hpp
@@ -1546,22 +1546,17 @@ public:
     return res;
   }
 
+  BOOST_NOINLINE void unchecked_rehash_for_growth()
+  {
+    auto new_arrays_=new_arrays_for_growth();
+    unchecked_rehash(new_arrays_);
+  }
+
   template<typename... Args>
   BOOST_NOINLINE locator
   unchecked_emplace_with_rehash(std::size_t hash,Args&&... args)
   {
-    /* Due to the anti-drift mechanism (see recover_slot), new_arrays_ may be
-     * of the same size as the old arrays; in the limit, erasing one element at
-     * full load and then inserting could bring us back to the same capacity
-     * after a costly rehash. To avoid this, we jump to the next capacity level
-     * when the number of erased elements is <= 10% of total elements at full
-     * load, which is implemented by requesting additional F*size elements,
-     * with F = P * 10% / (1 - P * 10%), where P is the probability of an
-     * element having caused overflow; P has been measured as ~0.162 under
-     * ideal conditions, yielding F ~ 0.0165 ~ 1/61.
-     */
-    auto    new_arrays_=new_arrays(std::size_t(
-              std::ceil(static_cast<float>(size()+size()/61+1)/mlf)));
+    auto    new_arrays_=new_arrays_for_growth();
     locator it;
     BOOST_TRY{
       /* strong exception guarantee -> try insertion before rehash */
@@ -1664,6 +1659,22 @@ private:
     return arrays_type::new_(al(),n);
   }
 
+  arrays_type new_arrays_for_growth()
+  {
+    /* Due to the anti-drift mechanism (see recover_slot), the new arrays may
+     * be of the same size as the old arrays; in the limit, erasing one
+     * element at full load and then inserting could bring us back to the same
+     * capacity after a costly rehash. To avoid this, we jump to the next
+     * capacity level when the number of erased elements is <= 10% of total
+     * elements at full load, which is implemented by requesting additional
+     * F*size elements, with F = P * 10% / (1 - P * 10%), where P is the
+     * probability of an element having caused overflow; P has been measured as
+     * ~0.162 under ideal conditions, yielding F ~ 0.0165 ~ 1/61.
+     */
+    return new_arrays(std::size_t(
+      std::ceil(static_cast<float>(size()+size()/61+1)/mlf)));
+  }
+
   void delete_arrays(arrays_type& arrays_)noexcept
   {
     arrays_type::delete_(al(),arrays_);