Skip futility pruning if ttMove has bad history

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 69d8decff3675d9412529bae3fe6593c28d90370..8510651360c07bd5f3c8540331749307d47e810a 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -780,7 +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)