Remove previousScore adjustment of delta.

STC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 14580 W: 2904 L: 2731 D: 8945
Ptnml(0-2): 243, 1665, 3339, 1762, 281
https://tests.stockfishchess.org/tests/view/5e7d080ae42a5c3b3ca2ebc6

LTC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 60338 W: 7870 L: 7831 D: 44637
Ptnml(0-2): 451, 5596, 18018, 5671, 433
https://tests.stockfishchess.org/tests/view/5e7d11b3e42a5c3b3ca2ebd3

closes https://github.com/official-stockfish/Stockfish/pull/2598

Bench 5247262

diff --git a/src/search.cpp b/src/search.cpp
index c5a7582ce4d1ccea45a67804983c3fde992bc3dc..f866afe5ce7b887747e80da04e79c6593a8713f2 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -433,7 +433,7 @@ void Thread::search() {
           if (rootDepth >= 4)
           {
               Value previousScore = rootMoves[pvIdx].previousScore;
-              delta = Value(21 + abs(previousScore) / 256);
+              delta = Value(21);
               alpha = std::max(previousScore - delta,-VALUE_INFINITE);
               beta  = std::min(previousScore + delta, VALUE_INFINITE);