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 more than 100k local KNPK games, there is no discernible difference between master and master with this endgame removed: master:42971, patch:42973, draws: 3969. Removal does not seem to regress in normal games.
STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 46390 W: 8998 L: 8884 D: 28508
Ptnml(0-2): 707, 5274, 11163, 5300, 751
https://tests.stockfishchess.org/tests/view/5e83b18ee42a5c3b3ca2ef02
LTC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 44768 W: 5863 L: 5814 D: 33091
Ptnml(0-2): 251, 3918, 14028, 3905, 282
https://tests.stockfishchess.org/tests/view/5e84a82a4411759d9d0984f4
In tests with a book of endgames that can convert into KNPK, no significant difference can be seen either
```
TC 1.0+0.01
Score of patch vs master: 6131 - 6188 - 27681 [0.499] 40000
Elo difference: -0.5 +/- 1.9, LOS: 30.4 %, DrawRatio: 69.2 %
TC 2.0+0.02
Score of patch vs master: 5740 - 5741 - 28519 [0.500] 40000
Elo difference: -0.0 +/- 1.8, LOS: 49.6 %, DrawRatio: 71.3 %
``
closes https://github.com/official-stockfish/Stockfish/pull/2611
Bench 4512059
Replace calls to count(key) + operator[key] with a single call to find(key).
Replace the std::map with std::unordered_map which provide O(1) access,
although the map has a really small number of objects.
Test with [0..4] failed yellow:
TC 10+0.1
SPRT elo0: 0.00 alpha: 0.05 elo1: 4.00 beta: 0.05
LLR -2.96 [-2.94,2.94] (rejected)
Elo 1.01 [-0.87,3.08] (95%)
LOS 85.3%
Games 71860 [w:22.3%, l:22.2%, d:55.5%]
http://tests.stockfishchess.org/tests/view/5d5432210ebc5925cf109d61
Closes https://github.com/official-stockfish/Stockfish/pull/2269
No functional change
Similar to PSQT we only need one instance of the Endgames resource. The current per thread copies are identical and read only(after initialization) so from a design point of view it doesn't make sense to have them.
Tested for no slowdown.
http://tests.stockfishchess.org/tests/view/5c94377a0ebc5925cfff43ca
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 17320 W: 3487 L: 3359 D: 10474
No functional change.
This is a somewhat different patch. It fixes blindspots for
two knights vs pawn endgame.
With local testing starting from random KNNvKP positions where the
pawn has not advanced beyond the 4th rank (thanks @protonspring !)
at 15+0.15 (4 cores), this went +105=868-27 against master. All except
two losses were won in reverse.
The heuristic is simple but effective - the strategy in these endgames
is to push the opposing king to the corner, then move the knight that's
blocking the pawn in for the checkmate while the pawn is free to move
and prevents stalemate. This patch gives SF the little boost it needs
to search the relevant king-cornering mating lines.
See the discussion in pull request 1939 for some more good results for
this test in independant tests:
https://github.com/official-stockfish/Stockfish/pull/1939
Bench: 3310239
Preparation commit for the upcoming Stockfish 10 version, giving a chance to catch last minute feature bugs and evaluation regression during the one-week code freeze period. Also changing the copyright dates to include 2019.
No functional change
Some warnings after a run of:
$ clang-tidy-3.8 -checks='modernize-*' *.cpp syzygy/*.cpp -header-filter=.* -- -std=c++11
I have not fixed all suggestions, for instance I still prefer
to declare the type instead of a spread use of 'auto'. I also
perfer good old 'typedef' to the new 'using' form.
I have not fixed some warnings in the last functions of
syzygy code because those are still the original functions
and need to be completely rewritten anyhow.
Thanks to erbsenzaehler for the original idea.
No functional change.
Warning is C4512 (assignment operator could not be generated)
Now, apart the foreign syzygy code, everything compiles
without warnings at warning level 4.
No functional change.
Coverity scan warns about uninitialized 'sf' argument when
calling probe(). Actually it is a false positive because
argument is passed by reference and assigned inside
probe(). Nevertheless it is a hint that fucntion signature
is a bit tricky, so rewrite it in a more conventional way,
assigning 'sf' from probe() return value.
No functional change.
Import C++11 branch from:
https://github.com/mcostalba/Stockfish/tree/c++11
The version imported is teh last one as of today:
6670e93e50
Branch is fully equivalent with master but syzygy
tablebases that are missing (but will be added with
next commit).
bench: 8080602
It is up to material (and pawn) table look up
code to know where the per-thread tables are,
so change API to reflect this.
Also some comment fixing while there
No functional change.
Retire KmmKm evaluation function. Instead give a very drawish
scale factor when the material advantage is small and not much
material remains.
Retire NoPawnsSF array. Pawnless endgames without a bishop will
now be scored higher. Pawnless endgames with a bishop pair will
be scored lower. The effect of this is hopefully small.
Consistent results both at short TC (fixed games):
ELO: -0.00 +-2.1 (95%) LOS: 50.0%
Total: 40000 W: 7405 L: 7405 D: 25190
And long TC (fixed games):
ELO: 0.77 +-1.9 (95%) LOS: 78.7%
Total: 39690 W: 6179 L: 6091 D: 27420
bench: 7213723
As pointed out by Joona, Lucas and otehr people in
the forum, this endgame is not a known, there are many
positions where it takes more than 50 moves to claim the
win and becasue exact rules is not possible better to
retire and allow the search to workout the endgame for us.
bench: 8502826
Dumb down a bit the code and trade some possible
speed (but this is far from hot path anyhow) for
some added readability for the layman.
No functional change.
The case of two lone kings on the board is already considered
by the "No pawns" scaling factor rules in material.cpp as is
KBK and KNK.
Moreover we had a small leak in endgames map because for
KK endgame it happens white and black material keys are the
same (both equal to zero), so when adding the black endgame in
Endgames::add() we were overwriting the already exsisting
white one, leading to a memory leak found by Valgrind.
So remove the endgames althogheter and rely on scaling
to correctly set the endgames value to a draw.
No functional change.
The endgame king + minor vs king is erroneusly
detected as king + minor vs king + minor
Here the fix is to detect king + minor earlier,
in particular to add these trivial cases to
endgame evaluation functions.
Spotted by Reuven Peleg
bench: 4727133
And #ifdef instead of #if defined
This is more standard form (see for example iostream file).
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
The 2 overload functions map() accept a pointer to
EndgameBase<Value> or a pointer to EndgameBase<ScaleFactor>.
Because Endgame<E> is derived from one of them we can
directly use a pointer to this class to resolve the
overload as is needed in Endgames::add().
Also made class Endgames fully parametrized and no more
hardcoded to the types (Value or ScaleFactor) of endgames
stored.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Allows some code semplification and avoids directly
allocation and managing heap memory.
Also the usual renaming while there.
No functional change and no speed regression.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This leads to a further and unexpected simplification
of this already very size optimized code.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is more idiomatic for a functor (a function object) as are
the endgames.
Suggested by Rein Halbersma.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
