From: Michael Chaly <Vizvezdenec@gmail.com>
Date: Fri, 8 Oct 2021 23:15:43 +0000 (+0300)
Subject: Reduce more if multiple moves exceed alpha
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=c8459b18ba2d6ddc76d6db90d6eab346ed682e69;hp=c8459b18ba2d6ddc76d6db90d6eab346ed682e69

Reduce more if multiple moves exceed alpha

Idea of this patch is the following: in case we already have four moves that
exceeded alpha in the current node, the probability of finding fifth should
be reasonably low. Note that four is completely arbitrary - there could and
probably should be some tweaks, both in tweaking best move count threshold
for more reductions and tweaking how they work - for example making more
reductions with best move count linearly.

passed STC:
https://tests.stockfishchess.org/tests/view/615f614783dd501a05b0aee2
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 141816 W: 36056 L: 35686 D: 70074
Ptnml(0-2): 499, 15131, 39273, 15511, 494

passed LTC:
https://tests.stockfishchess.org/tests/view/615fdff683dd501a05b0af35
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 68536 W: 17221 L: 16891 D: 34424
Ptnml(0-2): 38, 6573, 20725, 6885, 47

closes https://github.com/official-stockfish/Stockfish/pull/3736

Bench: 6131513
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