Fix incorrect pruning in qsearch

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 65ed9b73ffb0886e8e049a329587021c1965e466..743449fa39c5b7e13cd81dc68cd44f90d53fdf41 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1565,7 +1565,7 @@ moves_loop: // When in check, search starts from here
 
       // CounterMove based pruning
       if (  !captureOrPromotion
-          && moveCount
+          && bestValue > VALUE_TB_LOSS_IN_MAX_PLY
           && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
           && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold)
           continue;
@@ -1600,7 +1600,11 @@ moves_loop: // When in check, search starts from here
     // All legal moves have been searched. A special case: if we're in check
     // and no legal moves were found, it is checkmate.
     if (ss->inCheck && bestValue == -VALUE_INFINITE)
+    {
+        assert(!MoveList<LEGAL>(pos).size());
+
         return mated_in(ss->ply); // Plies to mate from the root
+    }
 
     tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
               bestValue >= beta ? BOUND_LOWER :