Simplify away improvement term in null move search

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 8bd5ec9b48bc4b48b244a97bb2d2a92a93dc6d4f..656558f87c472821f20898965dd0be30e8d47a1e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -779,7 +779,7 @@ namespace {
         && (ss-1)->statScore < 17329
         &&  eval >= beta
         &&  eval >= ss->staticEval
-        &&  ss->staticEval >= beta - 21 * depth - improvement / 13 + 258
+        &&  ss->staticEval >= beta - 21 * depth + 258
         && !excludedMove
         &&  pos.non_pawn_material(us)
         &&  ss->ply >= thisThread->nmpMinPly