Improve thread load balancing

kimwalisch · Oct 22, 2024 · 87be58a · 87be58a
1 parent bf8e09f
commit 87be58a
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diff --git a/ChangeLog b/ChangeLog
@@ -1,3 +1,8 @@
+Changes in version 12.5, 22/10/2024
+===================================
+
+* Improve thread load balancing for large number of CPU cores.
+
 Changes in version 12.4, 22/06/2024
 ===================================
 

diff --git a/src/ParallelSieve.cpp b/src/ParallelSieve.cpp
@@ -2,7 +2,7 @@
 /// @file   ParallelSieve.cpp
 /// @brief  Multi-threaded prime sieve using std::async.
 ///
-/// Copyright (C) 2023 Kim Walisch, <[email protected]>
+/// Copyright (C) 2024 Kim Walisch, <[email protected]>
 ///
 /// This file is distributed under the BSD License. See the COPYING
 /// file in the top level directory.
@@ -83,7 +83,7 @@ uint64_t ParallelSieve::getThreadDistance(int threads) const
   ASSERT(getDistance() > 0);
 
   uint64_t dist = getDistance();
-  uint64_t balanced = isqrt(stop_) * 1000;
+  uint64_t balanced = isqrt(stop_) * 200;
   uint64_t unbalanced = dist / threads;
   uint64_t fastest = std::min(balanced, unbalanced);
   uint64_t iters = dist / fastest;