Don't need to check for bestValue < beta to split

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 07405d42beed4a52f586d0ccae66c4b327797226..654efb3265f453caf9e8cfe398e04c625abc0b08 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -482,7 +482,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove, threatMove;
     Depth ext, newDepth;
-    Value bestValue, value, ttValue, ttValueUpper;
+    Value bestValue, value, ttValue;
     Value eval, nullValue, futilityValue;
     bool inCheck, givesCheck, pvMove, singularExtensionNode;
     bool captureOrPromotion, dangerous, doFullDepthSearch;
@@ -544,43 +544,31 @@ namespace {
     tte = TT.probe(posKey);
     ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
     ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
-    ttValueUpper = tte ? value_from_tt(tte->value_upper(), ss->ply) : VALUE_NONE;
 
     // At PV nodes we check for exact scores, while at non-PV nodes we check for
     // a fail high/low. Biggest advantage at probing at PV nodes is to have a
     // smooth experience in analysis mode. We don't probe at Root nodes otherwise
     // we should also update RootMoveList to avoid bogus output.
-    if (!RootNode && tte)
+    if (   !RootNode
+        && tte
+        && tte->depth() >= depth
+        && ttValue != VALUE_NONE // Only in case of TT access race
+        && (           PvNode ?  tte->type() == BOUND_EXACT
+            : ttValue >= beta ? (tte->type() & BOUND_LOWER)
+                              : (tte->type() & BOUND_UPPER)))
     {
-        // Fail High
-        if (  (tte->type() & BOUND_LOWER)
-            && ttValue >= beta
-            && tte->depth() >= depth
-            && ttValue != VALUE_NONE) // Only in case of TT access race
-        {
-            // Update killers, we assume ttMove caused a cut-off
-            if (    ttMove
-                && !pos.is_capture_or_promotion(ttMove)
-                &&  ttMove != ss->killers[0])
-            {
-                ss->killers[1] = ss->killers[0];
-                ss->killers[0] = ttMove;
-            }
-            TT.refresh(tte);
-            ss->currentMove = ttMove; // Can be MOVE_NONE
-            return ttValue;
-        }
+        TT.refresh(tte);
+        ss->currentMove = ttMove; // Can be MOVE_NONE
 
-        // Fail Low
-        if (  (tte->type() & BOUND_UPPER)
-            && ttValueUpper < beta
-            && tte->depth_upper() >= depth
-            && ttValueUpper != VALUE_NONE) // Only in case of TT access race
+        if (    ttValue >= beta
+            &&  ttMove
+            && !pos.is_capture_or_promotion(ttMove)
+            &&  ttMove != ss->killers[0])
         {
-            TT.refresh(tte);
-            ss->currentMove = ttMove; // Can be MOVE_NONE
-            return ttValueUpper;
+            ss->killers[1] = ss->killers[0];
+            ss->killers[0] = ttMove;
         }
+        return ttValue;
     }
 
     // Step 5. Evaluate the position statically and update parent's gain statistics
@@ -1015,9 +1003,10 @@ split_point_start: // At split points actual search starts from here
       // Step 19. Check for splitting the search
       if (   !SpNode
           &&  depth >= Threads.min_split_depth()
-          &&  bestValue < beta
           &&  Threads.available_slave_exists(thisThread))
       {
+          assert(bestValue < beta);
+
           bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
                                                depth, threatMove, moveCount, mp, NT);
           if (bestValue >= beta)
@@ -1101,7 +1090,7 @@ split_point_start: // At split points actual search starts from here
     const TTEntry* tte;
     Key posKey;
     Move ttMove, move, bestMove;
-    Value bestValue, value, ttValue, ttValueUpper, futilityValue, futilityBase, oldAlpha;
+    Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
     bool givesCheck, enoughMaterial, evasionPrunable, fromNull;
     Depth ttDepth;
 
@@ -1123,34 +1112,21 @@ split_point_start: // At split points actual search starts from here
     tte = TT.probe(posKey);
     ttMove = tte ? tte->move() : MOVE_NONE;
     ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
-    ttValueUpper = tte ? value_from_tt(tte->value_upper(),ss->ply) : VALUE_NONE;
 
     // Decide whether or not to include checks, this fixes also the type of
     // TT entry depth that we are going to use. Note that in qsearch we use
     // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
     ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
                                                   : DEPTH_QS_NO_CHECKS;
-    if (tte)
+    if (   tte
+        && tte->depth() >= ttDepth
+        && ttValue != VALUE_NONE // Only in case of TT access race
+        && (           PvNode ?  tte->type() == BOUND_EXACT
+            : ttValue >= beta ? (tte->type() & BOUND_LOWER)
+                              : (tte->type() & BOUND_UPPER)))
     {
-        // Fail High
-        if (  (tte->type() & BOUND_LOWER)
-            && ttValue >= beta
-            && tte->depth() >= ttDepth
-            && ttValue != VALUE_NONE) // Only in case of TT access race
-        {
-            ss->currentMove = ttMove; // Can be MOVE_NONE
-            return ttValue;
-        }
-
-        // Fail Low
-        if (  (tte->type() & BOUND_UPPER)
-            && ttValueUpper < beta
-            && tte->depth_upper() >= ttDepth
-            && ttValueUpper != VALUE_NONE) // Only in case of TT access race
-        {
-            ss->currentMove = ttMove; // Can be MOVE_NONE
-            return ttValueUpper;
-        }
+        ss->currentMove = ttMove; // Can be MOVE_NONE
+        return ttValue;
     }
 
     // Evaluate the position statically