Small cleanups

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index fcdb8d67545fd302ed782f743bc41b9cc6d53912..d6571a140f36b1e9ab5293895aff192df271a785 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -601,7 +601,6 @@ namespace {
 
     assert(0 <= ss->ply && ss->ply < MAX_PLY);
 
-    (ss+1)->ttPv         = false;
     (ss+1)->excludedMove = bestMove = MOVE_NONE;
     (ss+2)->killers[0]   = (ss+2)->killers[1] = MOVE_NONE;
     (ss+2)->cutoffCnt    = 0;
@@ -1071,11 +1070,10 @@ moves_loop: // When in check, search starts here
               && (tte->bound() & BOUND_LOWER)
               &&  tte->depth() >= depth - 3)
           {
-              Value singularBeta = ttValue - (2 + (ss->ttPv && !PvNode)) * depth;
+              Value singularBeta = ttValue - (3 + 2 * (ss->ttPv && !PvNode)) * depth / 2;
               Depth singularDepth = (depth - 1) / 2;
 
               ss->excludedMove = move;
-              // the search with excludedMove will update ss->staticEval
               value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
               ss->excludedMove = MOVE_NONE;
 
@@ -1104,11 +1102,15 @@ moves_loop: // When in check, search starts here
 
               // If the eval of ttMove is greater than beta, we reduce it (negative extension)
               else if (ttValue >= beta)
-                  extension = -2;
+                  extension = -2 - !PvNode;
 
               // If the eval of ttMove is less than value, we reduce it (negative extension)
               else if (ttValue <= value)
                   extension = -1;
+
+              // If the eval of ttMove is less than alpha, we reduce it (negative extension)
+              else if (ttValue <= alpha)
+                  extension = -1;
           }
 
           // Check extensions (~1 Elo)