Simplify Futility Pruning

Don't update bestValue when futility pruning.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 21933 W: 4031 L: 3912 D: 13990

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 46225 W: 6115 L: 6028 D: 34082

Bench: 8450534

diff --git a/src/search.cpp b/src/search.cpp
index 5f0a0f3b901e1bbdbbafd89ebafd98e0ea5950f9..f0ee1b2b90f628c389627c29a989c98936017322 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -606,7 +606,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth, predictedDepth;
-    Value bestValue, value, ttValue, eval, nullValue, futilityValue;
+    Value bestValue, value, ttValue, eval, nullValue;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
     bool captureOrPromotion, doFullDepthSearch;
     Piece moved_piece;
@@ -971,16 +971,9 @@ moves_loop: // When in check search starts from here
           predictedDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO);
 
           // Futility pruning: parent node
-          if (predictedDepth < 7 * ONE_PLY)
-          {
-              futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256;
-
-              if (futilityValue <= alpha)
-              {
-                  bestValue = std::max(bestValue, futilityValue);
-                  continue;
-              }
-          }
+          if (   predictedDepth < 7 * ONE_PLY
+              && ss->staticEval + futility_margin(predictedDepth) + 256 <= alpha)
+              continue;
 
           // Prune moves with negative SEE at low depths
           if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)