Allow any pawn in front of a minor piece to replace the pawn protection
requirement for outposts.
+-------+ +-------+
| . . o | | o . . | o Their pawns
| . o x | | o . . | x Our pawns
| o N . | | x o B | N,B New (reachable) outpost
| . . . | | . _ . | _ Reachable square behind a pawn
+-------+ +-------+
N outpost B reaches
outpost
We want outposts to be secured by pawns against major pieces. If
a minor is shielded by any pawn from above, it is rarely at the same
time protected by our pawn attacks from below. However, the pawn shield
in itself offers some degree of protection.
A pawn shield will now suffice to replace the pawn protection for the
outpost (and reachable outpost) bonus.
This effect stacks with the existing "minor behind pawn" bonus.
STC
https://tests.stockfishchess.org/tests/view/5f2bcd14b3ebe5cbfee85b2c
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 27248 W: 5353 L: 5119 D: 16776
Ptnml(0-2): 462, 3174, 6185, 3274, 529
LTC
https://tests.stockfishchess.org/tests/view/5f2bfef5b3ebe5cbfee85b5a
LLR: 2.96 (-2.94,2.94) {0.25,1.75}
Total: 99432 W: 12580 L: 12130 D: 74722
Ptnml(0-2): 696, 8903, 30049, 9391, 677
Closes#2935
Bench: 4143673
This patch ports the efficiently updatable neural network (NNUE) evaluation to Stockfish.
Both the NNUE and the classical evaluations are available, and can be used to
assign a value to a position that is later used in alpha-beta (PVS) search to find the
best move. The classical evaluation computes this value as a function of various chess
concepts, handcrafted by experts, tested and tuned using fishtest. The NNUE evaluation
computes this value with a neural network based on basic inputs. The network is optimized
and trained on the evalutions of millions of positions at moderate search depth.
The NNUE evaluation was first introduced in shogi, and ported to Stockfish afterward.
It can be evaluated efficiently on CPUs, and exploits the fact that only parts
of the neural network need to be updated after a typical chess move.
[The nodchip repository](https://github.com/nodchip/Stockfish) provides additional
tools to train and develop the NNUE networks.
This patch is the result of contributions of various authors, from various communities,
including: nodchip, ynasu87, yaneurao (initial port and NNUE authors), domschl, FireFather,
rqs, xXH4CKST3RXx, tttak, zz4032, joergoster, mstembera, nguyenpham, erbsenzaehler,
dorzechowski, and vondele.
This new evaluation needed various changes to fishtest and the corresponding infrastructure,
for which tomtor, ppigazzini, noobpwnftw, daylen, and vondele are gratefully acknowledged.
The first networks have been provided by gekkehenker and sergiovieri, with the latter
net (nn-97f742aaefcd.nnue) being the current default.
The evaluation function can be selected at run time with the `Use NNUE` (true/false) UCI option,
provided the `EvalFile` option points the the network file (depending on the GUI, with full path).
The performance of the NNUE evaluation relative to the classical evaluation depends somewhat on
the hardware, and is expected to improve quickly, but is currently on > 80 Elo on fishtest:
60000 @ 10+0.1 th 1
https://tests.stockfishchess.org/tests/view/5f28fe6ea5abc164f05e4c4c
ELO: 92.77 +-2.1 (95%) LOS: 100.0%
Total: 60000 W: 24193 L: 8543 D: 27264
Ptnml(0-2): 609, 3850, 9708, 10948, 4885
40000 @ 20+0.2 th 8
https://tests.stockfishchess.org/tests/view/5f290229a5abc164f05e4c58
ELO: 89.47 +-2.0 (95%) LOS: 100.0%
Total: 40000 W: 12756 L: 2677 D: 24567
Ptnml(0-2): 74, 1583, 8550, 7776, 2017
At the same time, the impact on the classical evaluation remains minimal, causing no significant
regression:
sprt @ 10+0.1 th 1
https://tests.stockfishchess.org/tests/view/5f2906a2a5abc164f05e4c5b
LLR: 2.94 (-2.94,2.94) {-6.00,-4.00}
Total: 34936 W: 6502 L: 6825 D: 21609
Ptnml(0-2): 571, 4082, 8434, 3861, 520
sprt @ 60+0.6 th 1
https://tests.stockfishchess.org/tests/view/5f2906cfa5abc164f05e4c5d
LLR: 2.93 (-2.94,2.94) {-6.00,-4.00}
Total: 10088 W: 1232 L: 1265 D: 7591
Ptnml(0-2): 49, 914, 3170, 843, 68
The needed networks can be found at https://tests.stockfishchess.org/nns
It is recommended to use the default one as indicated by the `EvalFile` UCI option.
Guidelines for testing new nets can be found at
https://github.com/glinscott/fishtest/wiki/Creating-my-first-test#nnue-net-tests
Integration has been discussed in various issues:
https://github.com/official-stockfish/Stockfish/issues/2823https://github.com/official-stockfish/Stockfish/issues/2728
The integration branch will be closed after the merge:
https://github.com/official-stockfish/Stockfish/pull/2825https://github.com/official-stockfish/Stockfish/tree/nnue-player-wip
closes https://github.com/official-stockfish/Stockfish/pull/2912
This will be an exciting time for computer chess, looking forward to seeing the evolution of
this approach.
Bench: 4746616
In some French games, Stockfish likes to bring the Knight to a bad outpost spot. This is evident in TCEC S18 Superfinal Game 63, where there is a Knight outpost on the queenside but is actually useless. Stockfish is effectively playing a piece down while holding ground against Leela's break on the kingside.
This patch turns the +56 mg bonus for a Knight outpost into a -7 mg penalty if it satisfies the following conditions:
* The outpost square is not on the CenterFiles (i.e. not on files C,D,E and F)
* The knight is not attacking non pawn enemies.
* The side where the outpost is located contains only few enemies, with a particular conditional_more_than_two() implementation
Thank you to apospa...@gmail.com for bringing this to our attention and for providing insights.
See https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/dEXNzSIBgZU
Reference game: https://tcec-chess.com/#div=sf&game=63&season=18
Passed STC:
LLR: 2.93 (-2.94,2.94) {-0.50,1.50}
Total: 6960 W: 1454 L: 1247 D: 4259
Ptnml(0-2): 115, 739, 1610, 856, 160
https://tests.stockfishchess.org/tests/view/5f08221059f6f0353289477e
Passed LTC:
LLR: 2.98 (-2.94,2.94) {0.25,1.75}
Total: 21440 W: 2767 L: 2543 D: 16130
Ptnml(0-2): 122, 1904, 6462, 2092, 140
https://tests.stockfishchess.org/tests/view/5f0838ed59f6f035328947a2
various related tests show strong test results, but so far no generalizations or simplifications of conditional_more_than_two() are found. See PR for details.
closes https://github.com/official-stockfish/Stockfish/pull/2803
Bench: 4366686
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
We replace the current decrease of the complexity term in initiative
when shuffling by a direct damping of the evaluation. This scheme may
have two benefits over the initiative approach:
a) the damping effect is more brutal for fortresses with heavy pieces
on the board, because the initiative term is almost an endgame term;
b) the initiative implementation had a funny side effect, almost a bug,
in the rare positions where mg > 0, eg < 0 and the tampered eval
returned a positive value (ie with heavy pieces still on the board):
sending eg to zero via shuffling would **increase** the tampered
eval instead of decreasing it, which is somewhat illogical. This
patch avoids this phenomenon.
STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 43072 W: 8373 L: 8121 D: 26578
Ptnml(0-2): 729, 4954, 9940, 5162, 751
https://tests.stockfishchess.org/tests/view/5ee008ebf29b40b0fc95ade2
LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 37376 W: 4816 L: 4543 D: 28017
Ptnml(0-2): 259, 3329, 11286, 3508, 306
https://tests.stockfishchess.org/tests/view/5ee03b06f29b40b0fc95ae0c
Closes https://github.com/official-stockfish/Stockfish/pull/2727
Bench: 4757174
This is a non-functional code style change which provides a safe access handler for LineBB.
Also includes an assert in debug mode to verify square correctness.
closes https://github.com/official-stockfish/Stockfish/pull/2719
No functional change
Merging this code into one function `winnable()`.
Should allow common concepts used to adjust the eg value,
either by addition or scaling, to be combined more effectively.
Improve trace function.
closes https://github.com/official-stockfish/Stockfish/pull/2710
No functional change.
The idea of this patch is that if rooks are not directly attacking the opponent king,
they can support king attacks staying behind pawns or minor pieces and be really
deadly if position slightly opens up at enemy king ring ranks. Loosely based on
some stockfish games where it underestimated attacks on it king when enemy has one
or two rooks supporting pawn pushes towards it king.
passed STC
https://tests.stockfishchess.org/tests/view/5ecb093680f2c838b96550f9
LLR: 2.93 (-2.94,2.94) {-0.50,1.50}
Total: 53672 W: 10535 L: 10265 D: 32872
Ptnml(0-2): 952, 6210, 12258, 6448, 968
passed LTC
https://tests.stockfishchess.org/tests/view/5ecb639f80f2c838b9655117
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 62424 W: 8094 L: 7748 D: 46582
Ptnml(0-2): 426, 5734, 18565, 6042, 445
closes https://github.com/official-stockfish/Stockfish/pull/2700
Bench: 4663220
This patch is a combinaison of two recent parameters tweaks which had
failed narrowly (yellow) at long time control:
• improvement in move ordering during search by softening the distinction
between bad captures and good captures during move generation, leading
to improved awareness of Stockfish of potential piece sacrifices (idea
by Rahul Dsilva)
• increase in the weight of pawns in the "initiative" part of the evaluation
function. With this change Stockfish should have more incentive to exchange
pawns when losing, and to keep pawns when winning.
STC:
LLR: 2.93 (-2.94,2.94) {-0.50,1.50}
Total: 10704 W: 2178 L: 1974 D: 6552
Ptnml(0-2): 168, 1185, 2464, 1345, 190
https://tests.stockfishchess.org/tests/view/5ec5553b377121ac09e1023d
LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 60592 W: 7835 L: 7494 D: 45263
Ptnml(0-2): 430, 5514, 18086, 5817, 449
https://tests.stockfishchess.org/tests/view/5ec55ca2377121ac09e10249
Closes https://github.com/official-stockfish/Stockfish/pull/2691
Bench: 4519117
simplify the usage of the 50 moves counter,
moving it frome the scale factor to initiative.
This patch was inspired by recent games where a blocked or semi-blocked position
was 'blundered', by moving a pawn, into a lost endgame. This patch improves this situation,
finding a more robust move more often.
for example (1s searches with many threads):
```
FEN 8/p3kp2/Pp2p3/1n2PpP1/5P2/1Kp5/8/R7 b - - 68 143
master:
6 bestmove b5c7
6 bestmove e7e8
12 bestmove e7d8
176 bestmove e7d7
patch:
3 bestmove b5c7
5 bestmove e7d8
192 bestmove e7d7
```
fixes https://github.com/official-stockfish/Stockfish/issues/2620
the patch also tests well
passed STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 50168 W: 9508 L: 9392 D: 31268
Ptnml(0-2): 818, 5873, 11616, 5929, 848
https://tests.stockfishchess.org/tests/view/5ebb07287dd5693aad4e680b
passed LTC
LLR: 2.93 (-2.94,2.94) {-1.50,0.50}
Total: 7520 W: 981 L: 870 D: 5669
Ptnml(0-2): 49, 647, 2256, 760, 48
https://tests.stockfishchess.org/tests/view/5ebbff747dd5693aad4e6858
closes https://github.com/official-stockfish/Stockfish/pull/2666
Bench: 4395562
This patch refines the recently introduced interaction between
the space bonus and the number of blocked pawns in a position.
* pawns count as blocked also if their push square is attacked by 2 enemy pawns;
* overall dependence is stronger as well as offset;
* bonus increase is capped at 9 blocked pawns in position;
passed STC
https://tests.stockfishchess.org/tests/view/5e94560663d105aebbab243d
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 29500 W: 5842 L: 5603 D: 18055
Ptnml(0-2): 504, 3443, 6677, 3562, 564
passed LTC
https://tests.stockfishchess.org/tests/view/5e95b383c2aaa99f75d1a14d
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 63504 W: 8329 L: 7974 D: 47201
Ptnml(0-2): 492, 5848, 18720, 6197, 495
closes https://github.com/official-stockfish/Stockfish/pull/2631
bench 4956028
+-------+
| o . . | o their pawns
| x . . | x our pawns
| . x . | <- Can sacrifice to create passer?
+-------+
yes
1 2 3 4 5
+-------+ +-------+ +-------+ +-------+ +-------+
| o . . | | o r . | | o r . | | o . b | | o . b | lowercase: theirs
| x b . | | x . . | | x . R | | x . R | | x . . | uppercase: ours
| . x . | | . x . | | . x . | | . x . | | . x B |
+-------+ +-------+ +-------+ +-------+ +-------+
no no yes no yes
The value of our top pawn depends on our ability to advance our bottom
pawn, levering their blocker. Previously, this pawn configuration was
always scored as passer (although a blocked one).
Add requirements for the square s above our (possibly) sacrificed pawn:
- s must not be occupied by them (1).
- If they attack s (2), we must attack s (3).
- If they attack s with a minor (4), we must attack s with a minor (5).
The attack from their blocker is ignored because it is inherent in the
structure; we are ok with sacrificing our bottom pawn.
LTC
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 37030 W: 4962 L: 4682 D: 27386
Ptnml(0-2): 266, 3445, 10863, 3625, 316
https://tests.stockfishchess.org/tests/view/5e92a2b4be6ede5b954bf239
STC
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 40874 W: 8066 L: 7813 D: 24995
Ptnml(0-2): 706, 4753, 9324, 4890, 764
https://tests.stockfishchess.org/tests/view/5e922199af0a0143109dc90e
closes https://github.com/official-stockfish/Stockfish/pull/2624
Bench: 4828294
Before this commit, some pawns were considered "candidate" passed pawns and given half bonus. After this commit, all of these pawns are scored as passed pawns, and they do not receive less bonus.
STC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 21806 W: 4320 L: 4158 D: 13328
Ptnml(0-2): 367, 2526, 5001, 2596, 413
https://tests.stockfishchess.org/tests/view/5e86b4724411759d9d098639
LTC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 12590 W: 1734 L: 1617 D: 9239
Ptnml(0-2): 96, 1187, 3645, 1238, 129
https://tests.stockfishchess.org/tests/view/5e86d2874411759d9d098640
This PR and commit are dedicated to our colleague Stefan Geschwentner (@locutus2), one of the most respected and accomplished members of the Stockfish developer community. Stockfish is a volunteer project and has always thrived because of Stefan's talent, insight, generosity, and dedication. Welcome back, Stefan!
closes https://github.com/official-stockfish/Stockfish/pull/2613
Bench: 4831963
