From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 10 Nov 2008 10:06:46 +0000 (+0100)
Subject: Use cut-off checks in qsearch as killer moves
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=e86468cc631ede99530998a6ad269e328f25f808

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 97ed196a..e2032638 100644
--- 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 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;
   }