Use cut-off checks in qsearch as killer moves

Killers should not be captures, but checks are not
and are produced also in qsearch.

Use this information, will be useful for move ordering.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/search.cpp b/src/search.cpp
index 97ed196acede459112754e6892f2b88fba8a75cc..e2032638b8650ce112968c4329ea4b08e77ee10e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1469,6 +1469,18 @@ namespace {
     // Update transposition table
     TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_EXACT);
 
     // Update transposition table
     TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_EXACT);
 

+    // Update killers only for good check moves
+    Move m = ss[ply].currentMove;
+    if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
+    {
+        // Wrong to update history when depth is <= 0
+
+        if (m != ss[ply].killer1)
+        {
+            ss[ply].killer2 = ss[ply].killer1;
+            ss[ply].killer1 = m;
+        }
+    }

     return bestValue;
   }
 
     return bestValue;
   }