Skip futility pruning if ttMove has bad history

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f49c23aed6571dcc8a6d024f3f2b813fb08a3290..8510651360c07bd5f3c8540331749307d47e810a 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -766,7 +766,8 @@ namespace {
     // Step 7. Razoring (~1 Elo)
     // If eval is really low check with qsearch if it can exceed alpha, if it can't,
     // return a fail low.
-    if (eval < alpha - 456 - 252 * depth * depth)
+    // Adjust razor margin according to cutoffCnt. (~1 Elo)
+    if (eval < alpha - 456 - (252 - 200 * ((ss+1)->cutoffCnt > 3)) * depth * depth)
     {
         value = qsearch<NonPV>(pos, ss, alpha - 1, alpha);
         if (value < alpha)
@@ -779,7 +780,10 @@ namespace {
         &&  depth < 9
         &&  eval - futility_margin(depth, cutNode && !ss->ttHit, improving) - (ss-1)->statScore / 306 >= beta
         &&  eval >= beta
-        &&  eval < 24923) // smaller than TB wins
+        &&  eval < 24923 // smaller than TB wins
+        && !(  !ttCapture
+             && ttMove
+             && thisThread->mainHistory[us][from_to(ttMove)] < 989))
         return eval;
 
     // Step 9. Null move search with verification search (~35 Elo)
@@ -983,7 +987,8 @@ moves_loop: // When in check, search starts here
           && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
       {
           // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~8 Elo)
-          moveCountPruning = moveCount >= futility_move_count(improving, depth);
+          if (!moveCountPruning)
+              moveCountPruning = moveCount >= futility_move_count(improving, depth);
 
           // Reduced depth of the next LMR search
           int lmrDepth = newDepth - r;