Introduce midgame initiative #2304
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snicolet
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Approved, congrats! You write:
I have measured the two probabilities P(A|B) and P(B|A) for using the following pieces of code: So indeed complexity is inferior to -50 in 99% of the one-flank endgames, but one-flank endgames are only 10% of the cases where complexity is inferior to -50 (and the patch applies). |
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Merged via 843a6c4, thanks! |
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well I mean that it's the most obvious case to my imagination. |
snicolet
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Sep 14, 2019
snicolet
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Sep 15, 2019
This patch decreases the endgame scale factor using the 50 moves counter. Looking at some games with this patch, this seems to have two effects on the playing style: 1) when no progress can be made in late endgames (for instance in fortresses or opposite bishops endgames) the evaluation will be largely tamed down toward a draw value. 2) more interestingly, there is also a small effect in the midgame play because Stockfish will panic a little bit if there are more than four consecutive shuffling moves with an advantage: the engine will try to move a pawn or to exchange a piece to keep the advantage, so the follow-ups of the position will be discovered earlier by the alpha-beta search. passed STC: LLR: 2.95 (-2.94,2.94) [0.50,4.50] Total: 23017 W: 5080 L: 4805 D: 13132 http://tests.stockfishchess.org/tests/view/5d7e4aef0ebc59069c36fc74 passed LTC: LLR: 2.95 (-2.94,2.94) [0.00,3.50] Total: 30746 W: 5171 L: 4911 D: 20664 http://tests.stockfishchess.org/tests/view/5d7e513d0ebc59069c36ff26 Pull request: official-stockfish/Stockfish#2304 Bench: 4272173
snicolet
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Sep 15, 2019
This patch decreases the endgame scale factor using the 50 moves counter. Looking at some games with this patch, it seems to have two effects on the playing style: 1) when no progress can be made in late endgames (for instance in fortresses or opposite bishops endgames) the evaluation will be largely tamed down towards a draw value. 2) more interestingly, there is also a small effect in the midgame play because Stockfish will panic a little bit if there are more than four consecutive shuffling moves with an advantage: the engine will try to move a pawn or to exchange a piece to keep the advantage, so the follow-ups of the position will be discovered earlier by the alpha-beta search. passed STC: LLR: 2.95 (-2.94,2.94) [0.50,4.50] Total: 23017 W: 5080 L: 4805 D: 13132 http://tests.stockfishchess.org/tests/view/5d7e4aef0ebc59069c36fc74 passed LTC: LLR: 2.95 (-2.94,2.94) [0.00,3.50] Total: 30746 W: 5171 L: 4911 D: 20664 http://tests.stockfishchess.org/tests/view/5d7e513d0ebc59069c36ff26 Pull request: #2304 Bench: 4272173
MichaelB7
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Sep 16, 2019
This patch decreases the endgame scale factor using the 50 moves counter. Looking at some games with this patch, this seems to have two effects on the playing style: 1) when no progress can be made in late endgames (for instance in fortresses or opposite bishops endgames) the evaluation will be largely tamed down toward a draw value. 2) more interestingly, there is also a small effect in the midgame play because Stockfish will panic a little bit if there are more than four consecutive shuffling moves with an advantage: the engine will try to move a pawn or to exchange a piece to keep the advantage, so the follow-ups of the position will be discovered earlier by the alpha-beta search. passed STC: LLR: 2.95 (-2.94,2.94) [0.50,4.50] Total: 23017 W: 5080 L: 4805 D: 13132 http://tests.stockfishchess.org/tests/view/5d7e4aef0ebc59069c36fc74 passed LTC: LLR: 2.95 (-2.94,2.94) [0.00,3.50] Total: 30746 W: 5171 L: 4911 D: 20664 http://tests.stockfishchess.org/tests/view/5d7e513d0ebc59069c36ff26 Pull request: official-stockfish#2304 Bench: 4272173
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Use fraction of negative complexity also in midgame evaluation
STC run was stopped after 200k games (and not converging):
http://tests.stockfishchess.org/tests/view/5d7cfdb10ebc5902d386572c
LLR: -1.75 (-2.94,2.94) [0.50,4.50]
Total: 200319 W: 44197 L: 43310 D: 112812
passed speculative LTC
http://tests.stockfishchess.org/tests/view/5d7d14680ebc5902d3866196
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 41051 W: 6858 L: 6570 D: 27623
This patch finally introduces something that was tried for years - midgame score dependance on complexity of position.
The most obvious field of play of this patch will be (again!) 4 vs 3 etc same flank endgames where sides have a lot of non-pawn material (4 vs 3 draw mostly remains the same draw even if we add a lot of equal material to both sides but eval will be much higher because we are further from endgame).
This is the first and not really precise version, a lot of other stuff can be tried on top of it (separate complexity for middlegame, some more terms, even simple retuning of values).
bench 4248476