Simplify reductions on singular extension
authorJoost VandeVondele <Joost.VandeVondele@gmail.com>
Mon, 21 Oct 2019 20:21:50 +0000 (22:21 +0200)
committerStéphane Nicolet <cassio@free.fr>
Wed, 23 Oct 2019 08:49:08 +0000 (10:49 +0200)
commit7e89a71624e07c735c2230dbbf2c7dbae864916e
tree8c5be735746af10af49fe353009e52607d74e449
parent215cd19108d97376284192c29790b42a0b0e618a
Simplify reductions on singular extension

Current master employs a scheme to adjust reductions on singular
nodes that is somewhat controversial, see
https://github.com/official-stockfish/Stockfish/pull/2167

This patch removes this use of a search result outside of [a,b],
by observing that the main effect of this code is to adjust the
reduction by an average of ~2 (1.7) rather than 1.

Claims the first blue at STC and LTC:

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 30142 W: 6547 L: 6442 D: 17153
http://tests.stockfishchess.org/tests/view/5daf16c40ebc5902c06da566

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 45715 W: 7380 L: 7298 D: 31037
http://tests.stockfishchess.org/tests/view/5daf2f3c0ebc5902c06da6c7

Closes https://github.com/official-stockfish/Stockfish/pull/2367

Bench: 5115841
src/search.cpp