Don't copy NNUE parts of StateInfo when not needed in do_null_move().
Measurement vs master at STC shows only ~3 Elo regression when NNUE
is not used, was ~5 Elo before.
https://tests.stockfishchess.org/tests/view/5f23a9052f7e63962b99f51b
ELO: -3.02 +-1.7 (95%) LOS: 0.0%
Total: 60000 W: 11145 L: 11666 D: 37189
Ptnml(0-2): 1018, 6945, 14494, 6626, 917
No functional change.
This is a non-functional simplification. Instead of passing the piece type
for remove_piece, we can rely on the board. The only exception is en-passant
which must be explicitly set because the destination square for the capture
is not the same as the piece to remove.
Verified also in the Chess960 castling case by running a couple of perft, see
the pull request discussion: https://github.com/official-stockfish/Stockfish/pull/2460
STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 18624 W: 4147 L: 4070 D: 10407
Ptnml(0-2): 223, 1933, 4945, 1938, 260
http://tests.stockfishchess.org/tests/view/5dfeaa93e70446e17e451163
No functional change
SEE (Static Exchange Evaluation) is a critical component, so we might
indulge some tricks to make it faster. Another pull request #2469 showed
some speedup by removing templates, this version uses Ronald de Man
(@syzygy1) SEE implementation which also unrolls the for loop by
suppressing the min_attacker() helper function and exits as soon as
the last swap is conclusive.
See Ronald de Man version there:
https://github.com/syzygy1/Cfish/blob/master/src/position.c
Patch testes against pull request #2469:
LLR: 2.95 (-2.94,2.94) {-1.00,3.00}
Total: 19365 W: 3771 L: 3634 D: 11960
Ptnml(0-2): 241, 1984, 5099, 2092, 255
http://tests.stockfishchess.org/tests/view/5e10eb135e5436dd91b27ba3
And since we are using new SPRT statistics, and that both pull requests
finished with less than 20000 games I also tested against master as
a speed-up:
LLR: 2.99 (-2.94,2.94) {-1.00,3.00}
Total: 18878 W: 3674 L: 3539 D: 11665
Ptnml(0-2): 193, 1999, 4966, 2019, 250
http://tests.stockfishchess.org/tests/view/5e10febf12ef906c8b388745
Non functional change
Store repetition info in StateInfo instead of recomputing it in
three different places. This saves some work in has_game_cycle()
where this info is needed for positions before the root.
Tested for non-regression at STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 34104 W: 7586 L: 7489 D: 19029
http://tests.stockfishchess.org/tests/view/5cd0676e0ebc5925cf044b56
No functional change.
In master search() may incorrectly return a draw score in the following
corner case: there was a 2-fold repetition during the game, and the
current position can be reached by a move from a repeated one. This case
is treated as an upcoming 3-fold repetition, which it is not.
Here is a testcase demonstrating the issue (note that the moves
after FEN are required). The input:
position fen 8/8/8/8/8/8/p7/2k4K b - - 0 1 moves c1b1 h1g1 b1c1 g1h1 c1b1 h1g1 b1a1 g1h1
go movetime 1000
produces the output:
[...]
info depth 127 seldepth 2 multipv 1 score cp 0 [...]
bestmove a1b1
saying that the game will be drawn by repetion. However the other possible
move for black, Kb2, avoids repetitions and wins. The patch fixes this behavior.
In particular it finds mate in 10 in the above position.
STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 10604 W: 2390 L: 2247 D: 5967
http://tests.stockfishchess.org/tests/view/5cb373e00ebc5925cf0167bf
LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 19620 W: 3308 L: 3185 D: 13127
http://tests.stockfishchess.org/tests/view/5cb3822f0ebc5925cf016b2d
Bench is not changed since it does not test positions with history of moves.
Bench: 3184182
Instead of looping through kfrom,kto, rfrom, rto, we can use BetweenBB. This is less lines of code and it is more clear what castlingPath actually is. Personal benchmarks are all over the place. However, this code is only executed when loading a position, so performance doesn't seem that relevant.
No functional change.
Adding a clamp function makes some of these range limitations a bit prettier and removes some #include's.
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 28117 W: 6300 L: 6191 D: 15626
http://tests.stockfishchess.org/tests/view/5c9aa1df0ebc5925cfff8fcc
Non functional change.
This changes 2 parts with regards to static exchange evaluation.
Currently, we do not allow pinned pieces to recapture if *all* opponent
pinners are still in their starting squares. This changes that to having
a less strict requirement, checking if *any* pinners are still in their
starting square. This makes our SEE give more respect to the pinning
side with regards to exchanges, which makes sense because it helps our
search explore more tactical options.
Furthermore, we change the logic for saving pinners into our state
variable when computing slider_blockers. We will include double pinners,
where two sliders may be looking at the same blocker, a similar concept
to our mobility calculation for sliders in our evaluation section.
Interestingly, I think SEE is the only place where the pinners bitboard
is actually used, so as far as I know there are no other side effects
to this change.
An example and some insights:
White Bf2, Kg1
Black Qe3, Bc5
The move Qg3 will be given the correct value of 0. (Previously < 0)
The move Qd4 will be incorrectly given a value of 0. (Previously < 0)
It seems the tradeoff in search is worth it. Qd4 will likely be pruned
soon by something like probcut anyway, while Qg3 could help us spot
tactics at an earlier depth.
STC:
LLR: 2.96 (-2.94,2.94) [0.50,4.50]
Total: 62162 W: 13879 L: 13408 D: 34875
http://tests.stockfishchess.org/tests/view/5c4ba1a70ebc593af5d49c55
LTC: (Thanks to @alayant)
LLR: 3.40 (-2.94,2.94) [0.00,3.50]
Total: 140285 W: 23416 L: 22825 D: 94044
http://tests.stockfishchess.org/tests/view/5c4bcfba0ebc593af5d49ea8
Bench: 3937213
Delay legality check of castling moves at search time,
just before making the move, as is the standard with all
the other move types.
This should avoid an useless and not trivial legality check
when the castling is then not tried later. For instance due
to a previous cut-off.
The patch is also a big simplification and allows to entirely
remove generate_castling()
Bench changes due to a different move sequence out of MovePicker.
STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 45073 W: 9918 L: 9843 D: 25312
http://tests.stockfishchess.org/tests/view/5c2f176f0ebc596a450bdfb3
LTC:
LLR: 3.15 (-2.94,2.94) [-3.00,1.00]
Total: 10156 W: 1707 L: 1560 D: 6889
http://tests.stockfishchess.org/tests/view/5c2e7dfd0ebc596a450bcdf4
Verified with perft both in standard and Chess960 cases.
Closes https://github.com/official-stockfish/Stockfish/pull/1929
Bench: 3559104
Joost VandeVondele