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 719fc0eac47fc9ac3ccbcf7dc75071670f9fa10b..53811de04701c4705053dc0d3ed1e52049db0aed 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1048,7 +1048,7 @@ namespace {
     EvalInfo ei;
 
     if (ply >= PLY_MAX - 1)
-        return evaluate(pos, ei, threadID);
+        return pos.is_check() ? quick_evaluate(pos) : evaluate(pos, ei, threadID);
 
     // Mate distance pruning
     Value oldAlpha = alpha;
@@ -1238,7 +1238,7 @@ namespace {
     EvalInfo ei;
 
     if (ply >= PLY_MAX - 1)
-        return evaluate(pos, ei, threadID);
+        return pos.is_check() ? quick_evaluate(pos) : evaluate(pos, ei, threadID);
 
     // Mate distance pruning
     if (value_mated_in(ply) >= beta)
@@ -1369,7 +1369,8 @@ namespace {
       {
           // 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
@@ -1529,8 +1530,8 @@ namespace {
     else
         staticValue = evaluate(pos, ei, threadID);
 
-    if (ply == PLY_MAX - 1)
-        return evaluate(pos, ei, threadID);
+    if (ply >= PLY_MAX - 1)
+        return pos.is_check() ? quick_evaluate(pos) : evaluate(pos, ei, threadID);
 
     // Initialize "stand pat score", and return it immediately if it is
     // at least beta.