From: joergoster <osterj165@googlemail.com>
Date: Wed, 21 Sep 2016 12:02:35 +0000 (+0200)
Subject: Allowing singular extension in mate positions
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=351844061eddffac59e7a3c2d16af7ea9661bb3e;hp=351844061eddffac59e7a3c2d16af7ea9661bb3e

Allowing singular extension in mate positions

Drop useless condition

abs(ttValue) < VALUE_KNOWN_WIN

And extend singular extension search to cases when ttValue
stores a mate score. This improves mate finding and does
not introduce any regression.

Yery tested this patch against current master on the 6500+
Chest mate suite with 200K fixed nodes:

    shortest mates found: master: 1206 patch:1205
    any mate found: master: 1903 patch: 2003

with 1 sec time:

    shortest mates found: master: 2667 patch: 2628
    any mate found: master: 3585 patch: 3646

Verified for no regression:

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25655 W: 4578 L: 4465 D: 16612

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66247 W: 8618 L: 8557 D: 49072

bench: 6335042
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