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https://github.com/sockspls/badfish
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7caa6cd338
Adds support for Syzygy tablebases to Stockfish. See the Readme for information on using the tablebases. Tablebase support can be enabled/disabled at the Makefile level as well, by setting syzygy=yes or syzygy=no. Big/little endian are both supported. No functional change (if Tablebases are not used). Resolves #6
112 lines
4.8 KiB
Markdown
112 lines
4.8 KiB
Markdown
### Overview
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Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is
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not a complete chess program and requires some UCI-compatible GUI
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(e.g. XBoard with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess
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Partner or Fritz) in order to be used comfortably. Read the
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documentation for your GUI of choice for information about how to use
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Stockfish with it.
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This version of Stockfish supports up to 128 cores. The engine defaults
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to one search thread, so it is therefore recommended to inspect the value of
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the *Threads* UCI parameter, and to make sure it equals the number of CPU
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cores on your computer.
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This version of Stockfish has support for Syzygybases.
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### Files
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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
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that can be used to compile Stockfish on Unix-like systems.
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### Syzygybases
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**Configuration**
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Syzygybases are configured using the UCI options "SyzygyPath",
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"SyzygyProbeDepth", "Syzygy50MoveRule" and "SyzygyProbeLimit".
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The option "SyzygyPath" should be set to the directory or directories that
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contain the .rtbw and .rtbz files. Multiple directories should be
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separated by ";" on Windows and by ":" on Unix-based operating systems.
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**Do not use spaces around the ";" or ":".**
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Example: `C:\tablebases\wdl345;C:\tablebases\wdl6;D:\tablebases\dtz345;D:\tablebases\dtz6`
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It is recommended to store .rtbw files on an SSD. There is no loss in
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storing the .rtbz files on a regular HD.
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Increasing the "SyzygyProbeDepth" option lets the engine probe less
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aggressively. Set this option to a higher value if you experience too much
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slowdown (in terms of nps) due to TB probing.
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Set the "Syzygy50MoveRule" option to false if you want tablebase positions
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that are drawn by the 50-move rule to count as win or loss. This may be useful
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for correspondence games (because of tablebase adjudication).
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The "SyzygyProbeLimit" option should normally be left at its default value.
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**What to expect**
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If the engine is searching a position that is not in the tablebases (e.g.
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a position with 7 pieces), it will access the tablebases during the search.
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If the engine reports a very large score (typically 123.xx), this means
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that it has found a winning line into a tablebase position.
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If the engine is given a position to search that is in the tablebases, it
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will use the tablebases at the beginning of the search to preselect all
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good moves, i.e. all moves that preserve the win or preserve the draw while
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taking into account the 50-move rule.
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It will then perform a search only on those moves. **The engine will not move
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immediately**, unless there is only a single good move. **The engine likely
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will not report a mate score even if the position is known to be won.**
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It is therefore clear that behaviour is not identical to what one might
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be used to with Nalimov tablebases. There are technical reasons for this
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difference, the main technical reason being that Nalimov tablebases use the
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DTM metric (distance-to-mate), while Syzygybases use a variation of the
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DTZ metric (distance-to-zero, zero meaning any move that resets the 50-move
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counter). This special metric is one of the reasons that Syzygybases are
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more compact than Nalimov tablebases, while still storing all information
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needed for optimal play and in addition being able to take into account
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the 50-move rule.
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### Compiling it yourself
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On Unix-like systems, it should be possible to compile Stockfish
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directly from the source code with the included Makefile.
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Stockfish has support for 32 or 64-bit CPUs, the hardware POPCNT
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instruction, big-endian machines such as Power PC, and other platforms.
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In general it is recommended to run `make help` to see a list of make
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targets with corresponding descriptions. When not using the Makefile to
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compile (for instance with Microsoft MSVC) you need to manually
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set/unset some switches in the compiler command line; see file *types.h*
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for a quick reference.
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### Terms of use
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Stockfish is free, and distributed under the **GNU General Public License**
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(GPL). Essentially, this means that you are free to do almost exactly
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what you want with the program, including distributing it among your
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friends, making it available for download from your web site, selling
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it (either by itself or as part of some bigger software package), or
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using it as the starting point for a software project of your own.
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The only real limitation is that whenever you distribute Stockfish in
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some way, you must always include the full source code, or a pointer
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to where the source code can be found. If you make any changes to the
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source code, these changes must also be made available under the GPL.
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For full details, read the copy of the GPL found in the file named
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*Copying.txt*
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