Revert futility pruning patches

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f412d9d6f1a1573fefbadeccdbed2d7513115ca9..c48b74bcc76ddc0761cdb9c44d961dffa4b0f2c0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -779,8 +779,10 @@ namespace {
                ? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
                : ss->staticEval > (ss-2)->staticEval;
 
-    // Step 7. Futility pruning: child node (~50 Elo)
+    // Step 7. Futility pruning: child node (~50 Elo).
+    // The depth condition is important for mate finding.
     if (   !PvNode
+        &&  depth < 9
         &&  eval - futility_margin(depth, improving) >= beta
         &&  eval < VALUE_KNOWN_WIN) // Do not return unproven wins
         return eval;
@@ -907,7 +909,7 @@ namespace {
         && !ttMove)
         depth -= 2;
 
-moves_loop: // When in check, search starts from here
+moves_loop: // When in check, search starts here
 
     ttCapture = ttMove && pos.capture_or_promotion(ttMove);
 
@@ -989,7 +991,7 @@ moves_loop: // When in check, search starts from here
       // Calculate new depth for this move
       newDepth = depth - 1;
 
-      // Step 13. Pruning at shallow depth (~200 Elo)
+      // Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding.
       if (  !rootNode
           && pos.non_pawn_material(us)
           && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
@@ -1017,21 +1019,18 @@ moves_loop: // When in check, search starts from here
           {
               // Continuation history based pruning (~20 Elo)
               if (   lmrDepth < 5
-                  && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
-                  && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
+                  && (*contHist[0])[movedPiece][to_sq(move)] < 23 - 23 * depth * depth
+                  && (*contHist[1])[movedPiece][to_sq(move)] < 23 - 23 * depth * depth)
                   continue;
 
               // Futility pruning: parent node (~5 Elo)
               if (   !ss->inCheck
-                  && ss->staticEval + 174 + 157 * lmrDepth <= alpha
-                  &&  (*contHist[0])[movedPiece][to_sq(move)]
-                    + (*contHist[1])[movedPiece][to_sq(move)]
-                    + (*contHist[3])[movedPiece][to_sq(move)]
-                    + (*contHist[5])[movedPiece][to_sq(move)] / 3 < 28255)
+                  && lmrDepth < 7
+                  && ss->staticEval + 174 + 157 * lmrDepth <= alpha)
                   continue;
 
               // Prune moves with negative SEE (~20 Elo)
-              if (!pos.see_ge(move, Value(-(30 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
+              if (!pos.see_ge(move, Value(-21 * lmrDepth * lmrDepth - 21 * lmrDepth)))
                   continue;
           }
       }