Remove Capture Extension

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 2abfbaf2f3dd35d6f0fb414a03fa13b327bcca90..eb0ac5bbd02c856c2a9d85989af21f22eafcacf5 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -69,9 +69,9 @@ namespace {
   // Reductions lookup table, initialized at startup
   int Reductions[MAX_MOVES]; // [depth or moveNumber]
 
-  Depth reduction(bool i, Depth d, int mn, bool rangeReduction) {
+  Depth reduction(bool i, Depth d, int mn, bool rangeReduction, Value delta, Value rootDelta) {
     int r = Reductions[d] * Reductions[mn];
-    return (r + 534) / 1024 + (!i && r > 904) + rangeReduction;
+    return (r + 1358 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 904) + rangeReduction;
   }
 
   constexpr int futility_move_count(bool improving, Depth depth) {
@@ -1015,6 +1015,8 @@ moves_loop: // When in check, search starts here
       // Calculate new depth for this move
       newDepth = depth - 1;
 
+      Value delta = beta - alpha;
+
       // Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding.
       if (  !rootNode
           && pos.non_pawn_material(us)
@@ -1024,7 +1026,7 @@ moves_loop: // When in check, search starts here
           moveCountPruning = moveCount >= futility_move_count(improving, depth);
 
           // Reduced depth of the next LMR search
-          int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0);
+          int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta), 0);
 
           if (   captureOrPromotion
               || givesCheck)
@@ -1035,6 +1037,16 @@ moves_loop: // When in check, search starts here
                   && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
                   continue;
 
+              // Futility pruning for captures
+              if (   !pos.empty(to_sq(move))
+                  && !givesCheck
+                  && !PvNode
+                  && lmrDepth < 6
+                  && !ss->inCheck
+                  && ss->staticEval + 342 + 238 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))] 
+                   + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 8 < alpha)
+                  continue;
+
               // SEE based pruning
               if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
                   continue;
@@ -1052,8 +1064,6 @@ moves_loop: // When in check, search starts here
 
               history += thisThread->mainHistory[us][from_to(move)];
 
-              lmrDepth = std::max(0, lmrDepth - (beta - alpha < thisThread->rootDelta / 4));
-
               // Futility pruning: parent node (~5 Elo)
               if (   !ss->inCheck
                   && lmrDepth < 8
@@ -1113,12 +1123,6 @@ moves_loop: // When in check, search starts here
               extension = -2;
       }
 
-      // Capture extensions for PvNodes and cutNodes
-      else if (   (PvNode || cutNode)
-               && captureOrPromotion
-               && moveCount != 1)
-          extension = 1;
-
       // Check extensions
       else if (   givesCheck
                && depth > 6
@@ -1161,12 +1165,11 @@ moves_loop: // When in check, search starts here
               || !captureOrPromotion
               || (cutNode && (ss-1)->moveCount > 1)))
       {
-          Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
+          Depth r = reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta);
 
           // Decrease reduction at some PvNodes (~2 Elo)
           if (   PvNode
-              && bestMoveCount <= 3
-              && beta - alpha >= thisThread->rootDelta / 4)
+              && bestMoveCount <= 3)
               r--;
 
           // Decrease reduction if position is or has been on the PV
@@ -1175,10 +1178,6 @@ moves_loop: // When in check, search starts here
               && !likelyFailLow)
               r -= 2;
 
-          // Increase reduction at non-PV nodes (~3 Elo)
-          if (!PvNode)
-              r++;
-
           // Decrease reduction if opponent's move count is high (~1 Elo)
           if ((ss-1)->moveCount > 13)
               r--;