Scale down eval for queen imbalance
authorStéphane Nicolet <cassio@free.fr>
Sun, 28 Jun 2020 20:24:57 +0000 (22:24 +0200)
committerStéphane Nicolet <cassio@free.fr>
Sun, 28 Jun 2020 20:42:43 +0000 (22:42 +0200)
commitc7194bd924a606ab75d582d30cb41749312ea94e
treeb8441faa0c3925f93e8c1d628dad3e2a1a400e03
parent16836f39b295ec635c9883498400f7006ac2869f
Scale down eval for queen imbalance

We lower the endgame value of the evaluation when we detect that there
is only one queen left on the board (more precisely, we use a scale
factor of 37/64, or about 0.58, for the endgame part of the evaluation).
Hopefully this helps a little bit for the assessment of positions with
queen imbalance, which are one of the well-known Stockfish weaknesses.

STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 21600 W: 4176 L: 3955 D: 13469
Ptnml(0-2): 351, 2457, 5003, 2598, 391
https://tests.stockfishchess.org/tests/view/5ef871b6020eec13834a94e8

LTC:
LLR: 2.97 (-2.94,2.94) {0.25,1.75}
Total: 248328 W: 30596 L: 29720 D: 188012
Ptnml(0-2): 1544, 22345, 75665, 22911, 1699
https://tests.stockfishchess.org/tests/view/5ef87aec020eec13834a94fe

Closes https://github.com/official-stockfish/Stockfish/pull/2781

Bench: 4441323
src/evaluate.cpp