- remove the blank line between the declaration of the function and it's
comment, leads to better IDE support when hovering over a function to see it's
description
- remove the unnecessary duplication of the function name in the functions
description
- slightly refactored code for lsb, msb in bitboard.h There are still a few
things we can be improved later on, move the description of a function where
it was declared (instead of implemented) and add descriptions to functions
which are behind macros ifdefs
closes https://github.com/official-stockfish/Stockfish/pull/4840
No functional change
This introduces clang-format to enforce a consistent code style for Stockfish.
Having a documented and consistent style across the code will make contributing easier
for new developers, and will make larger changes to the codebase easier to make.
To facilitate formatting, this PR includes a Makefile target (`make format`) to format the code,
this requires clang-format (version 17 currently) to be installed locally.
Installing clang-format is straightforward on most OS and distros
(e.g. with https://apt.llvm.org/, brew install clang-format, etc), as this is part of quite commonly
used suite of tools and compilers (llvm / clang).
Additionally, a CI action is present that will verify if the code requires formatting,
and comment on the PR as needed. Initially, correct formatting is not required, it will be
done by maintainers as part of the merge or in later commits, but obviously this is encouraged.
fixes https://github.com/official-stockfish/Stockfish/issues/3608
closes https://github.com/official-stockfish/Stockfish/pull/4790
Co-Authored-By: Joost VandeVondele <Joost.VandeVondele@gmail.com>
The original idea is the reverse of a previous patch [1] which added bonuses
in our move picker to moves escaping threats. In this patch, in addition to
bonuses for evading threats, we apply penalties to moves moving to threatened
squares.
Further tweaks of that basic idea resulted in this specific version which
further increases the penalty of moves moving to squares threatend depending
on the piece threatening it. So for example a queen moving to a square attacked
by a pawn would receive a larger penalty than a queen moving to square attacked
by a rook.
[1]: 08e0f52b77
--------
Passed STC:
https://tests.stockfishchess.org/tests/live_elo/64c11269dc56e1650abb935d
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 95552 W: 24654 L: 24250 D: 46648
Ptnml(0-2): 322, 11098, 24562, 11442, 352
Passed LTC:
https://tests.stockfishchess.org/tests/live_elo/64c2004ddc56e1650abba8b3
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 190230 W: 48806 L: 48178 D: 93246
Ptnml(0-2): 90, 20439, 53453, 21019, 114
-------
closes https://github.com/official-stockfish/Stockfish/pull/4711
Bench: 1350831
Patch analyzes field after SEE exchanges concluded with a recapture by
the opponent:
if opponent Queen/Rook/King results under attack after the exchanges, we
consider the move sharp and don't prune it.
Important note:
By accident I forgot to adjust 'occupied' when the king takes part in
the exchanges.
As result of this a move is considered sharp too, when opponent king
apparently can evade check by recapturing.
Surprisingly this seems contribute to patch's strength.
STC:
https://tests.stockfishchess.org/tests/view/640b16132644b62c33947397
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 116400 W: 31239 L: 30817 D: 54344
Ptnml(0-2): 350, 12742, 31618, 13116, 374
LTC:
https://tests.stockfishchess.org/tests/view/640c88092644b62c3394c1c5
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 177600 W: 47988 L: 47421 D: 82191
Ptnml(0-2): 62, 16905, 54317, 17436, 80
closes https://github.com/official-stockfish/Stockfish/pull/4453
bench: 5012145
in a some of cases movepicker returned some moves more than once which lead
to them being searched more than once. This bug was possible because of how
we use queen promotions - they are generated as a captures but are not
included in position function which checks if move is a capture. Thus if
any refutation (killer or countermove) was a queen promotion it was
searched twice - once as a capture and one as a refutation.
This patch affects various things, namely stats assignments for queen promotions
and other moves if best move is queen promotion,
also some heuristics in search and qsearch.
With this patch every queen promotion is now considered a capture.
After this patch number of found duplicated moves is 0 during normal 13 depth bench run.
Passed STC:
https://tests.stockfishchess.org/tests/view/63f77e01e74a12625bcd87d7
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 80920 W: 21455 L: 21289 D: 38176
Ptnml(0-2): 198, 8839, 22241, 8963, 219
Passed LTC:
https://tests.stockfishchess.org/tests/view/63f7e020e74a12625bcd9a76
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 89712 W: 23674 L: 23533 D: 42505
Ptnml(0-2): 24, 8737, 27202, 8860, 33
closes https://github.com/official-stockfish/Stockfish/pull/4405
bench 4681731
This idea is a mix of koivisto idea of threat history and heuristic that
was simplified some time ago in LMR - decreasing reduction for moves that evade a capture.
Instead of doing so in LMR this patch does it in movepicker - to do this it
calculates squares that are attacked by different piece types and pieces that are located
on this squares and boosts up weight of moves that make this pieces land on a square that is not under threat.
Boost is greater for pieces with bigger material values.
Special thanks to koivisto and seer authors for explaining me ideas behind threat history.
Passed STC:
https://tests.stockfishchess.org/tests/view/62406e473b32264b9aa1478b
LLR: 2.94 (-2.94,2.94) <0.00,2.50>
Total: 19816 W: 5320 L: 5072 D: 9424
Ptnml(0-2): 86, 2165, 5172, 2385, 100
Passed LTC:
https://tests.stockfishchess.org/tests/view/62407f2e3b32264b9aa149c8
LLR: 2.94 (-2.94,2.94) <0.50,3.00>
Total: 51200 W: 13805 L: 13500 D: 23895
Ptnml(0-2): 44, 5023, 15164, 5322, 47
closes https://github.com/official-stockfish/Stockfish/pull/3970
bench 7736491
- "discovered check" (instead of "discovery check")
- "en passant" (instead of "en-passant")
- "pseudo-legal" before a noun (instead of "pseudo legal")
- "3-fold" (instead of "3fold")
closes https://github.com/official-stockfish/Stockfish/pull/3294
No functional change.
The idea of this patch can be described as following: we update static
history stats based on comparison of the static evaluations of the
position before and after the move. If the move increases static evaluation
it's assigned positive bonus, if it decreases static evaluation
it's assigned negative bonus. These stats are used in movepicker
to sort quiet moves.
passed STC
https://tests.stockfishchess.org/tests/view/5fca4c0842a050a89f02cd66
LLR: 3.00 (-2.94,2.94) {-0.25,1.25}
Total: 78152 W: 7409 L: 7171 D: 63572
Ptnml(0-2): 303, 5695, 26873, 5871, 334
passed LTC
https://tests.stockfishchess.org/tests/view/5fca6be442a050a89f02cd75
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 40240 W: 1602 L: 1441 D: 37197
Ptnml(0-2): 19, 1306, 17305, 1475, 15
closes https://github.com/official-stockfish/Stockfish/pull/3253
bench 3845156
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
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
In master, if the received ttMove meets the prescribed conditions in the various MovePicker constructors, it is returned as the first move, otherwise we set it to MOVE_NONE. If set to MOVE_NONE, we no longer track what the ttMove was, and it will might be returned later in a list of generated moves. This may be a waste. With this patch, if the ttMove fails to meet the prescribed conditions, we simply skip the TT stages, but still store the move and make sure it's never returned.
STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 66424 W: 12903 L: 12806 D: 40715
Ptnml(0-2): 1195, 7730, 15230, 7897, 1160
LTC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 45682 W: 5989 L: 5926 D: 33767
Ptnml(0-2): 329, 4361, 13443, 4334, 374
closes https://github.com/official-stockfish/Stockfish/pull/2616
Bench 4928928
Current move histories are known to work well near the leaves, whilst at
higher depths they aren't very helpful. To address this problem this
patch introduces a table dedicated for what's happening at plies 0-3.
It's structured like mainHistory with ply index instead of color.
It get cleared with each new search and is filled during iterative
deepening at higher depths when recording successful quiet moves near
the root or traversing nodes which were in the principal variation
(ttPv).
Medium TC (20+0.2):
https://tests.stockfishchess.org/tests/view/5e4d358790a0a02810d096dc
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 100910 W: 16682 L: 16376 D: 67852
Ptnml(0-2): 1177, 10983, 25883, 11181, 1231
LTC:
https://tests.stockfishchess.org/tests/view/5e4e2cb790a0a02810d09714
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 80444 W: 10495 L: 10095 D: 59854
Ptnml(0-2): 551, 7479, 23803, 7797, 592
closes https://github.com/official-stockfish/Stockfish/pull/2557
Bench: 4705960
Simplification that eliminates ONE_PLY, based on a suggestion in the forum that
support for fractional plies has never been used, and @mcostalba's openness to
the idea of eliminating it. We lose a little bit of type safety by making Depth
an integer, but in return we simplify the code in search.cpp quite significantly.
No functional change
------------------------------------------
The argument favoring eliminating ONE_PLY:
* The term “ONE_PLY” comes up in a lot of forum posts (474 to date)
https://groups.google.com/forum/?fromgroups=#!searchin/fishcooking/ONE_PLY%7Csort:relevance
* There is occasionally a commit that breaks invariance of the code
with respect to ONE_PLY
https://groups.google.com/forum/?fromgroups=#!searchin/fishcooking/ONE_PLY%7Csort:date/fishcooking/ZIPdYj6k0fk/KdNGcPWeBgAJ
* To prevent such commits, there is a Travis CI hack that doubles ONE_PLY
and rechecks bench
* Sustaining ONE_PLY has, alas, not resulted in any improvements to the
engine, despite many individuals testing many experiments over 5 years.
The strongest argument in favor of preserving ONE_PLY comes from @locutus:
“If we use par example ONE_PLY=256 the parameter space is increases by the
factor 256. So it seems very unlikely that the optimal setting is in the
subspace of ONE_PLY=1.”
There is a strong theoretical impediment to fractional depth systems: the
transposition table uses depth to determine when a stored result is good
enough to supply an answer for a current search. If you have fractional
depths, then different pathways to the position can be at fractionally
different depths.
In the end, there are three separate times when a proposal to remove ONE_PLY
was defeated by the suggestion to “give it a few more months.” So… it seems
like time to remove this distraction from the community.
See the pull request here:
https://github.com/official-stockfish/Stockfish/pull/2289
