Decrease reduction for killer moves with good history

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 41096c9c7d2b751fd019c28b6fa2409284021907..7d618a65b56442e595fbf75dc9fc4cd9dd8ffedb 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1164,6 +1164,11 @@ moves_loop: // When in check, search starts here
       if ((ss+1)->cutoffCnt > 3)
           r++;
 
+      // Decrease reduction if move is a killer and we have a good history
+      if (move == ss->killers[0]
+          && (*contHist[0])[movedPiece][to_sq(move)] >= 3600)
+          r--;
+
       ss->statScore =  2 * thisThread->mainHistory[us][from_to(move)]
                      + (*contHist[0])[movedPiece][to_sq(move)]
                      + (*contHist[1])[movedPiece][to_sq(move)]