Increase reduction if tt-move is a capture

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 5447ed3c6694c74b398effebbe3ad41a704e9778..12cbffe020b25f7bf92921dc860e23e83eb3d919 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -554,7 +554,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
     Piece moved_piece;
     int moveCount, quietCount;
 
@@ -842,6 +842,7 @@ moves_loop: // When in check search starts from here
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
     skipQuiets = false;
+    ttCapture = false;
 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
@@ -959,6 +960,9 @@ moves_loop: // When in check search starts from here
           ss->moveCount = --moveCount;
           continue;
       }
+      
+      if (move == ttMove && captureOrPromotion)
+          ttCapture = true;
 
       // Update the current move (this must be done after singular extension search)
       ss->currentMove = move;
@@ -979,6 +983,11 @@ moves_loop: // When in check search starts from here
               r -= r ? ONE_PLY : DEPTH_ZERO;
           else
           {
+          
+              // Increase reduction if ttMove is a capture
+              if (ttCapture)
+                  r += ONE_PLY;
+          
               // Increase reduction for cut nodes
               if (cutNode)
                   r += 2 * ONE_PLY;
@@ -1262,9 +1271,6 @@ moves_loop: // When in check search starts from here
     {
       assert(is_ok(move));
 
-      // Speculative prefetch as early as possible
-      prefetch(TT.first_entry(pos.key_after(move)));
-
       givesCheck =  type_of(move) == NORMAL && !pos.discovered_check_candidates()
                   ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move)
                   : pos.gives_check(move);
@@ -1306,6 +1312,9 @@ moves_loop: // When in check search starts from here
           &&  !pos.see_ge(move))
           continue;
 
+      // Speculative prefetch as early as possible
+      prefetch(TT.first_entry(pos.key_after(move)));
+
       // Check for legality just before making the move
       if (!pos.legal(move))
       {