Adjust futility pruning base in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c2d35796231b0b9ebcb4a5645553e343a28d46b5..24f54c32bb35537231576690f35e4bb479f70667 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -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)
@@ -1499,7 +1495,7 @@ moves_loop: // When in check, search starts here
         if (bestValue > alpha)
             alpha = bestValue;
 
-        futilityBase = bestValue + 200;
+        futilityBase = std::min(ss->staticEval, bestValue) + 200;
     }
 
     const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,