From: Marco Costalba <mcostalba@gmail.com>
Date: Fri, 13 Nov 2009 10:25:34 +0000 (+0100)
Subject: Null move dynamic reduction based on value
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=314faa905a60962595d610c26727c4b603c6ed62;ds=sidebyside

Null move dynamic reduction based on value

After 994 games at 1+0

Mod vs Orig +244 =521 -229 50.75%  504.5/994 +5 ELO

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

diff --git a/src/search.cpp b/src/search.cpp
index d654fec9..e0252932 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1314,7 +1314,13 @@ namespace {
         ss[ply].currentMove = MOVE_NULL;
 
         pos.do_null_move(st);
-        int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
+
+        // Null move dynamic reduction based on depth
+        int R = (depth >= 5 * OnePly ? 4 : 3);
+
+        // Null move dynamic reduction based on value
+        if (approximateEval - beta > PawnValueMidgame)
+            R++;
 
         nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);