0ad9b51dea
Based on vondele's deletepsqt branch: https://github.com/vondele/Stockfish/commit/369f5b051 This huge simplification uses a weighted material differences instead of the positional piece square tables (psqt) in the semi-classical complexity calculation. Tuned weights using spsa at 45+0.45 with: int pawnMult = 100; int knightMult = 325; int bishopMult = 350; int rookMult = 500; int queenMult = 900; TUNE(SetRange(0, 200), pawnMult); TUNE(SetRange(0, 650), knightMult); TUNE(SetRange(0, 700), bishopMult); TUNE(SetRange(200, 800), rookMult); TUNE(SetRange(600, 1200), queenMult); The values obtained via this tuning session were for a model where the psqt replacement formula was always from the point of view of White, even if the side to move was Black. We re-used the same values for an implementation with a psqt replacement from the point of view of the side to move, testing the result both on our standard book on positions with a strong White bias, and an alternate book with positions with a strong Black bias. We note that with the patch the last use of the venerable "Score" type disappears in Stockfish codebase (the Score type was used in classical evaluation to get a tampered eval interpolating values smoothly from the early midgame stage to the endgame stage). We leave it to another commit to clean all occurrences of Score in the code and the comments. ------- Passed non-regression LTC: LLR: 2.94 (-2.94,2.94) <-1.75,0.25> Total: 142542 W: 36264 L: 36168 D: 70110 Ptnml(0-2): 76, 15578, 39856, 15696, 65 https://tests.stockfishchess.org/tests/view/64c8cb495b17f7c21c0cf9f8 Passed non-regression LTC (with a book with Black bias): https://tests.stockfishchess.org/tests/view/64c8f9295b17f7c21c0cfdaf LLR: 2.94 (-2.94,2.94) <-1.75,0.25> Total: 494814 W: 125565 L: 125827 D: 243422 Ptnml(0-2): 244, 53926, 139346, 53630, 261 ------ closes https://github.com/official-stockfish/Stockfish/pull/4713 Bench: 1655985 |
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| src | ||
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| CITATION.cff | ||
| Copying.txt | ||
| README.md | ||
| Top CPU Contributors.txt | ||
Stockfish
A free and strong UCI chess engine.
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Overview
Stockfish is a free and strong UCI chess engine derived from Glaurung 2.1 that analyzes chess positions and computes the optimal moves.
Stockfish does not include a graphical user interface (GUI) that is required to display a chessboard and to make it easy to input moves. These GUIs are developed independently from Stockfish and are available online. Read the documentation for your GUI of choice for information about how to use Stockfish with it.
See also the Stockfish documentation for further usage help.
Files
This distribution of Stockfish consists of the following files:
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README.md, the file you are currently reading.
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Copying.txt, a text file containing the GNU General Public License version 3.
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AUTHORS, a text file with the list of authors for the project.
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src, a subdirectory containing the full source code, including a Makefile that can be used to compile Stockfish on Unix-like systems.
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a file with the .nnue extension, storing the neural network for the NNUE evaluation. Binary distributions will have this file embedded.
The UCI protocol
The Universal Chess Interface (UCI) is a standard text-based protocol used to communicate with a chess engine and is the recommended way to do so for typical graphical user interfaces (GUI) or chess tools. Stockfish implements the majority of its options.
Developers can see the default values for the UCI options available in Stockfish
by typing ./stockfish uci in a terminal, but most users should typically use a
chess GUI to interact with Stockfish.
For more information on UCI or debug commands, see our documentation.
Compiling Stockfish
Stockfish has support for 32 or 64-bit CPUs, certain hardware instructions, big-endian machines such as Power PC, and other platforms.
On Unix-like systems, it should be easy to compile Stockfish directly from the
source code with the included Makefile in the folder src. In general, it is
recommended to run make help to see a list of make targets with corresponding
descriptions. An example suitable for most Intel and AMD chips:
cd src
make -j profile-build ARCH=x86-64-avx2
Detailed compilation instructions for all platforms can be found in our documentation.
Contributing
Donating hardware
Improving Stockfish requires a massive amount of testing. You can donate your hardware resources by installing the Fishtest Worker and viewing the current tests on Fishtest.
Improving the code
In the chessprogramming wiki, many techniques used in Stockfish are explained with a lot of background information. The section on Stockfish describes many features and techniques used by Stockfish. However, it is generic rather than focused on Stockfish's precise implementation.
The engine testing is done on Fishtest. If you want to help improve Stockfish, please read this guideline first, where the basics of Stockfish development are explained.
Discussions about Stockfish take place these days mainly in the Stockfish Discord server. This is also the best place to ask questions about the codebase and how to improve it.
Terms of use
Stockfish is free and distributed under the GNU General Public License version 3 (GPL v3). Essentially, this means you are free to do almost exactly what you want with the program, including distributing it among your friends, making it available for download from your website, selling it (either by itself or as part of some bigger software package), or using it as the starting point for a software project of your own.
The only real limitation is that whenever you distribute Stockfish in some way, you MUST always include the license and the full source code (or a pointer to where the source code can be found) to generate the exact binary you are distributing. If you make any changes to the source code, these changes must also be made available under GPL v3.