Improve play for closed positions
authorStéphane Nicolet <cassio@free.fr>
Thu, 21 Jan 2021 17:53:29 +0000 (18:53 +0100)
committerJoost VandeVondele <Joost.VandeVondele@gmail.com>
Sat, 30 Jan 2021 12:20:56 +0000 (13:20 +0100)
commit1188141aa78d01c361582daaa73de5154b6d09b1
tree201171302fab12b02ce6afa3e8b9c2f1b2329917
parentb7f643fe391d00fd9088587e8ef0ca520fa1480f
Improve play for closed positions

This patch give a small bonus to incite the attacking side to keep more
pawns on the board.

A consequence of this bonus is that Stockfish will tend to play positions
slightly more closed on average than master, especially when it believes
that it has an advantage.

To lower the risk of blockades where Stockfish start shuffling without
progress, we also implement a progressive decrease of the evaluation
value with the 50 moves counter (along with the necessary aging of the
transposition table to reduce the impact of the Graph History Interaction
problem): since the evaluation decreases during shuffling phases, the
engine will tend to examine the consequences of pawn breaks faster during
the search.

Passed STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 26184 W: 2406 L: 2252 D: 21526
Ptnml(0-2): 85, 1784, 9223, 1892, 108
https://tests.stockfishchess.org/tests/view/600cc08b735dd7f0f0352c06

Passed LCT:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 199768 W: 7695 L: 7191 D: 184882
Ptnml(0-2): 85, 6478, 86269, 6952, 100
https://tests.stockfishchess.org/tests/view/600ccd28735dd7f0f0352c10

Closes https://github.com/official-stockfish/Stockfish/pull/3321

Bench: 3988915
src/evaluate.cpp
src/position.cpp
src/position.h