Adjust futility pruning base in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index db9a5a8d01d2a0d729f7e6d390e8995f502b9ffa..24f54c32bb35537231576690f35e4bb479f70667 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -616,7 +616,7 @@ namespace {
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && !excludedMove
-        && tte->depth() > depth - (tte->bound() == BOUND_EXACT)
+        && tte->depth() > depth
         && ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit
         && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
     {
@@ -745,8 +745,8 @@ namespace {
     }
 
     // Set up the improving flag, which is true if current static evaluation is
-    // bigger than the previous static evaluation at our turn (if we were in 
-    // check at our previous move we look at static evaluaion at move prior to it
+    // bigger than the previous static evaluation at our turn (if we were in
+    // check at our previous move we look at static evaluation at move prior to it
     // and if we were in check at move prior to it flag is set to true) and is
     // false otherwise. The improving flag is used in various pruning heuristics.
     improving =   (ss-2)->staticEval != VALUE_NONE ? ss->staticEval > (ss-2)->staticEval
@@ -1037,7 +1037,7 @@ moves_loop: // When in check, search starts here
               lmrDepth = std::max(lmrDepth, 0);
 
               // Prune moves with negative SEE (~4 Elo)
-              if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth)))
+              if (!pos.see_ge(move, Value(-31 * lmrDepth * lmrDepth)))
                   continue;
           }
       }
@@ -1104,10 +1104,6 @@ moves_loop: // When in check, search starts here
               // If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
               else if (ttValue <= value)
                   extension = -1;
-
-              // If the eval of ttMove is less than alpha, we reduce it (negative extension) (~1 Elo)
-              else if (ttValue <= alpha)
-                  extension = -1;
           }
 
           // Check extensions (~1 Elo)
@@ -1496,10 +1492,10 @@ moves_loop: // When in check, search starts here
             return bestValue;
         }
 
-        if (PvNode && bestValue > alpha)
+        if (bestValue > alpha)
             alpha = bestValue;
 
-        futilityBase = bestValue + 200;
+        futilityBase = std::min(ss->staticEval, bestValue) + 200;
     }
 
     const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
@@ -1608,7 +1604,7 @@ moves_loop: // When in check, search starts here
                 if (PvNode) // Update pv even in fail-high case
                     update_pv(ss->pv, move, (ss+1)->pv);
 
-                if (PvNode && value < beta) // Update alpha here!
+                if (value < beta) // Update alpha here!
                     alpha = value;
                 else
                     break; // Fail high