Do not prune the move if we are still under mate

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index c0b6507ce9ecddeffac44bc2bea2df64ed7d2de7..53811de04701c4705053dc0d3ed1e52049db0aed 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1369,7 +1369,8 @@ namespace {
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)
       {
           // History pruning. See ok_to_prune() definition
           if (   moveCount >= 2 + int(depth)

-              && ok_to_prune(pos, move, ss[ply].threatMove, depth))
+              && ok_to_prune(pos, move, ss[ply].threatMove, depth)
+              && bestValue > value_mated_in(PLY_MAX))

               continue;
 
           // Value based pruning
               continue;
 
           // Value based pruning