From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 23 Sep 2008 11:03:44 +0000 (+0200)
Subject: Do not use evaluate() for razoring
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=060eef4f4e97ea1261252256c6768b243b7d3de5

Do not use evaluate() for razoring

Because razoring is reached 10% of times and about 50% of time
first two conditions are met we can save 5% of calls to the fairly
costly evaluate().

On the other side statistics have shown 95% of nodes that pass
the first two razoring conditions pass also the evaluate() test.
So the risk of dropping the third condition seems low enough.

Testing seems to validate this.

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

diff --git a/src/search.cpp b/src/search.cpp
index 88d3e8a0..c2974dcf 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1122,9 +1122,7 @@ namespace {
         }
     }
     // Null move search not allowed, try razoring
-    else if (   depth < RazorDepth
-             && approximateEval < beta - RazorMargin
-             && evaluate(pos, ei, threadID) < beta - RazorMargin)
+    else if (depth < RazorDepth && approximateEval < beta - RazorMargin)
     {
         Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
         if (v < beta)