Add doubled isolated pawn penalty.
authorStefan Geschwentner <stgeschwentner@gmail.com>
Fri, 22 May 2020 09:08:44 +0000 (11:08 +0200)
committerStéphane Nicolet <cassio@free.fr>
Fri, 22 May 2020 18:40:24 +0000 (20:40 +0200)
commitcdf5cfdb92b4ac7df8c2c3d891797787081c1ca2
tree73c3533d62221c02a8db9b8c32ac9547a4befd29
parent09c6917d053582267a2960e8c375883e0d9461da
Add doubled isolated pawn penalty.

This patch gives an additional penalty if a doubled isolated pawn is stopped
only by a single opponent pawn on the same file. Thanks to NKONSTANTAKIS,
who shared this idea on the forum!

https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/vC4Qn-PMlS4.

STC:
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 84872 W: 16688 L: 16370 D: 51814
Ptnml(0-2): 1507, 9940, 19274, 10158, 1557
https://tests.stockfishchess.org/tests/view/5ec65bd955202b947dc5d4ac

LTC:
LLR: 2.93 (-2.94,2.94) {0.25,1.75}
Total: 58104 W: 7614 L: 7278 D: 43212
Ptnml(0-2): 411, 5369, 17196, 5625, 451
https://tests.stockfishchess.org/tests/view/5ec6e9f2c23f5b0710632b19

Closes https://github.com/official-stockfish/Stockfish/pull/2694

Bench: 5148950
src/pawns.cpp