Tweak CMH pruning

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 66843515e4ddc332ddae523814fd52099d399533..c589f2369c2cf72d256de89734cbae52d0d1c185 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -973,7 +973,7 @@ moves_loop: // When in check, search starts from here
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
-              if (   lmrDepth < 3 + ((ss-1)->statScore > 0)
+              if (   lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
                   && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;