Refine stat based reductions

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 3da3d04ea963e579b7d2c6154015eb7cc1a8ee19..7abffb8779dda1df915c660577a6ebd9330eb559 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1233,7 +1233,13 @@ moves_loop: // When in check, search starts from here
                   r++;
 
               // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-              r -= ss->statScore / 14884;
+              // If we are not in check use statScore, if we are in check 
+              // use sum of main history and first continuation history with an offset
+              if (ss->inCheck)
+                  r -= (thisThread->mainHistory[us][from_to(move)] 
+                     + (*contHist[0])[movedPiece][to_sq(move)] - 4333) / 16384;
+              else
+                  r -= ss->statScore / 14884;
           }
 
           Depth d = std::clamp(newDepth - r, 1, newDepth);