Further increase reductions with increasing number of threads

This patch doubles the reduction increase with thread count.

passed STC
https://tests.stockfishchess.org/tests/view/5e874f5a4411759d9d098696
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 9162 W: 1558 L: 1385 D: 6219
Ptnml(0-2): 90, 958, 2343, 1069, 121

passed LTC
https://tests.stockfishchess.org/tests/view/5e8762804411759d9d09869f
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 79364 W: 9541 L: 9159 D: 60664
Ptnml(0-2): 462, 6880, 24661, 7172, 507

closes https://github.com/official-stockfish/Stockfish/pull/2615

bench 4831963

diff --git a/src/search.cpp b/src/search.cpp
index eb30d9fac8cd50c9cfc72ec1309e30a014579376..cfda94b8080110112b1bac35b20472fd09719e22 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -194,7 +194,7 @@ namespace {
 void Search::init() {
 
   for (int i = 1; i < MAX_MOVES; ++i)
-      Reductions[i] = int((24.8 + std::log(Threads.size()) / 2) * std::log(i));
+      Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i));
 }