From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 9 Nov 2008 12:03:52 +0000 (+0100)
Subject: Smaller null move reduction when depth is high
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=e7bad2687a26655e128fec04b58bbcdaaaf910cd;p=fairystockfish.git

Smaller null move reduction when depth is high

Lower probability to miss something important.

It seems to increase strenght. Idea form Cyclone.

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

diff --git a/src/search.cpp b/src/search.cpp
index 8da1211..97ed196 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1148,7 +1148,8 @@ namespace {
 
         UndoInfo u;
         pos.do_null_move(u);
-        Value nullValue = -search(pos, ss, -(beta-1), depth-4*OnePly, ply+1, false, threadID);
+        int R = (depth > 7 ? 4 : 3);
+        Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
         pos.undo_null_move(u);
 
         if (nullValue >= beta)