Maximize usage of transposition table in probcut

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 720a910093216be07e52c00cec03789c918c6891..6cf2f90d409f96dbe4f6a88ce625d71341153493 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -596,7 +596,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
-    Value bestValue, value, ttValue, eval, maxValue;
+    Value bestValue, value, ttValue, eval, maxValue, probcutBeta;
     bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
          ttCapture, singularQuietLMR;
@@ -871,23 +871,33 @@ namespace {
         }
     }
 
+    probcutBeta = beta + 176 - 49 * improving;
+
     // Step 10. ProbCut (~10 Elo)
     // If we have a good enough capture and a reduced search returns a value
     // much above beta, we can (almost) safely prune the previous move.
     if (   !PvNode
         &&  depth > 4
-        &&  abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
+        &&  abs(beta) < VALUE_TB_WIN_IN_MAX_PLY
+        && !(   ttHit
+             && tte->depth() >= depth - 3
+             && ttValue != VALUE_NONE
+             && ttValue < probcutBeta))
     {
-        Value raisedBeta = beta + 176 - 49 * improving;
-        assert(raisedBeta < VALUE_INFINITE);
-        MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory);
+        if (   ttHit
+            && tte->depth() >= depth - 3
+            && ttValue != VALUE_NONE
+            && ttValue >= probcutBeta
+            && ttMove
+            && pos.capture_or_promotion(ttMove))
+            return probcutBeta;
+
+        assert(probcutBeta < VALUE_INFINITE);
+        MovePicker mp(pos, ttMove, probcutBeta - ss->staticEval, &captureHistory);
         int probCutCount = 0;
 
         while (   (move = mp.next_move()) != MOVE_NONE
-               && probCutCount < 2 + 2 * cutNode
-               && !(   move == ttMove
-                    && tte->depth() >= depth - 4
-                    && ttValue < raisedBeta))
+               && probCutCount < 2 + 2 * cutNode)
             if (move != excludedMove && pos.legal(move))
             {
                 assert(pos.capture_or_promotion(move));
@@ -905,16 +915,21 @@ namespace {
                 pos.do_move(move, st);
 
                 // Perform a preliminary qsearch to verify that the move holds
-                value = -qsearch<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1);
+                value = -qsearch<NonPV>(pos, ss+1, -probcutBeta, -probcutBeta+1);
 
                 // If the qsearch held, perform the regular search
-                if (value >= raisedBeta)
-                    value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4, !cutNode);
+                if (value >= probcutBeta)
+                    value = -search<NonPV>(pos, ss+1, -probcutBeta, -probcutBeta+1, depth - 4, !cutNode);
 
                 pos.undo_move(move);
 
-                if (value >= raisedBeta)
+                if (value >= probcutBeta)
+                {
+                    tte->save(posKey, value_to_tt(value, ss->ply), ttPv,
+                        BOUND_LOWER,
+                        depth - 3, move, ss->staticEval);
                     return value;
+                }
             }
     }