mirror of
https://github.com/sockspls/badfish
synced 2025-05-01 17:19:36 +00:00
166bf90e41
There is no need to make this as large as 65536 just for the sake of the single 7-man tablebase that happens to have the key 0xf9247fff. Idea for the fix by Ronald de Man, who suggested simply to allow more buckets past the end. We also implement Robin Hood hashing for the hash table, which takes the worst -case search for full 7-man tablebases down from 68 to 11 probes (Also takes the average probe length from 2.06 to 2.05). For a table with 8K entries, the corresponding numbers would be worst-case from 9 to 4, with average from 1.30 to 1.29. https://github.com/official-stockfish/Stockfish/pull/1747 No functional change
123 lines
5.8 KiB
Markdown
123 lines
5.8 KiB
Markdown
### Overview
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[](https://travis-ci.org/official-stockfish/Stockfish)
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[](https://ci.appveyor.com/project/mcostalba/stockfish)
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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 512 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 8 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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### Resource For Understanding the Code Base
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* [Chess Programming Wiki](https://chessprogramming.wikispaces.com) has good overall chess engines explanations
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(techniques used here are well explained like hash maps etc), it was
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also recommended by the [support team at stockfish.](http://support.stockfishchess.org/discussions/questions/1132-how-to-understand-stockfish-sources)
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* [Here](https://chessprogramming.wikispaces.com/Stockfish) you can find a set of features and techniques used by stockfish and each of them is explained at the wiki, however, it's a generic way rather than focusing on stockfish's own implementation, but it will still help you.
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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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