Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is not a complete chess program and requires some UCI-compatible GUI (e.g. XBoard with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess Partner or Fritz) in order to be used comfortably. Read the documentation for your GUI of choice for information about how to use Stockfish with it.
This version of Stockfish supports up to 64 CPUs, but has not been tested thoroughly with more than 4. The program tries to detect the number of CPUs on your computer and sets the number of search threads accordingly, but please be aware that the detection is not always correct. It is therefore recommended to inspect the value of the Threads UCI parameter, and to make sure it equals the number of CPU cores on your computer. If you are using more than eight threads, it is recommended to raise the value of the Min Split Depth UCI parameter to 7.
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.
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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. For further information about how to compile Stockfish yourself read section below.
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polyglot.ini, for using Stockfish with Fabien Letouzey's PolyGlot adapter.
This version of Stockfish has support for PolyGlot opening books. For information about how to create such books, consult the PolyGlot documentation. The book file can be selected by setting the Book File UCI parameter.
On Unix-like systems, it should be possible to compile Stockfish directly from the source code with the included Makefile.
Stockfish has support for 32 or 64-bit CPUs, the hardware POPCNT instruction, big-endian machines such as Power PC, and other platforms.
In general it is recommended to run make help to see a list of make
targets with corresponding descriptions. When not using Makefile to
compile (for instance with Microsoft MSVC) you need to manually
set/unset some switches in the compiler command line; see file types.h
for a quick reference.
Stockfish is free, and distributed under the GNU General Public License (GPL). Essentially, this means that 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 web site, 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 full source code, or a pointer to where the source code can be found. If you make any changes to the source code, these changes must also be made available under the GPL.
For full details, read the copy of the GPL found in the file named Copying.txt