From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 2 Oct 2012 04:18:21 +0000 (+0200)
Subject: Further push singular extension
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=4c91dbc28e8bb6265f80240de26b8e02f7020a51

Further push singular extension

Extend for an extra half-ply in case the node is (probably)
going to fail high. In this case the added overhead is limited.

A novelity is the way this patch has been tested: Always in
self-play but with a much longer TC to allow the singular
extension to fully kick in and also (my impression) to have
less noisy results.

Ater 1015 games on my QUAD at 60"+0.05
Mod vs Orig 173 - 150 - 692 ELO +8
---

diff --git a/src/search.cpp b/src/search.cpp
index abb5116d..163df7b4 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -863,7 +863,7 @@ split_point_start: // At split points actual search starts from here
           ss->excludedMove = MOVE_NONE;
 
           if (value < rBeta)
-              ext = ONE_PLY;
+              ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY;
       }
 
       // Update current move (this must be done after singular extension search)