Modify singular beta for ttPv positions.

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 9562bf8640d4e8b04772d0e915281107e6218f97..c8a35a36d2f079906bf8f38a46775c95b7727262 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1048,7 +1048,7 @@ moves_loop: // When in check, search starts from here
           &&  tte->depth() >= depth - 3
           &&  pos.legal(move))
       {
-          Value singularBeta = ttValue - 2 * depth;
+          Value singularBeta = ttValue - (((ttPv && !PvNode) + 4) * depth) / 2;
           Depth halfDepth = depth / 2;
           ss->excludedMove = move;
           value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode);