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https://github.com/sockspls/badfish
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This exploits the recent fractional Skill Level, and is a result from some discussion in #2221 and the older #758. Basically, if UCI_LimitStrength is set, it will internally convert UCI_Elo to a matching fractional Skill Level. The Elo estimate is based on games at TC 60+0.6, Hash 64Mb, 8moves_v3.pgn, rated with Ordo, anchored to goldfish1.13 (CCRL 40/4 ~2000). Note that this is mostly about internal consistency, the anchoring to CCRL is a bit weak, e.g. within this tournament, goldfish and sungorus only have a 200Elo difference, their rating difference on CCRL is 300Elo. I propose that we continue to expose 'Skill Level' as an UCI option, for backwards compatibility. The result of a tournament under those conditions are given by the following table, where the player name reflects the UCI_Elo. # PLAYER : RATING ERROR POINTS PLAYED (%) CFS(%) 1 Elo2837 : 2792.2 50.8 536.5 711 75 100 2 Elo2745 : 2739.0 49.0 487.5 711 69 100 3 Elo2654 : 2666.4 49.2 418.0 711 59 100 4 Elo2562 : 2604.5 38.5 894.5 1383 65 100 5 Elo2471 : 2515.2 38.1 651.5 924 71 100 6 Elo2380 : 2365.9 35.4 478.5 924 52 100 7 Elo2289 : 2290.0 28.0 864.0 1596 54 100 8 sungorus1.4 : 2204.9 27.8 680.5 1596 43 60 9 Elo2197 : 2201.1 30.1 523.5 924 57 100 10 Elo2106 : 2103.8 24.5 730.5 1428 51 100 11 Elo2014 : 2030.5 30.3 377.5 756 50 98 12 goldfish1.13 : 2000.0 ---- 511.0 1428 36 100 13 Elo1923 : 1928.5 30.9 641.5 1260 51 100 14 Elo1831 : 1829.0 42.1 370.5 756 49 100 15 Elo1740 : 1738.3 42.9 277.5 756 37 100 16 Elo1649 : 1625.0 42.1 525.5 1260 42 100 17 Elo1558 : 1521.5 49.9 298.0 756 39 100 18 Elo1467 : 1471.3 51.3 246.5 756 33 100 19 Elo1375 : 1407.1 51.9 183.0 756 24 --- It can be observed that all set Elos correspond within the error bars with the observed Ordo rating. No functional change
202 lines
8.6 KiB
Markdown
202 lines
8.6 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/branch/master)
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[Stockfish](https://stockfishchess.org) is a free, powerful UCI chess engine
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derived from Glaurung 2.1. It is not a complete chess program and requires a
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UCI-compatible GUI (e.g. XBoard with PolyGlot, Scid, Cute Chess, eboard, Arena,
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Sigma Chess, Shredder, Chess Partner or Fritz) in order to be used comfortably.
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Read the documentation for your GUI of choice for information about how to use
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Stockfish with it.
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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 version 3.
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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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## UCI parameters
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Currently, Stockfish has the following UCI options:
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* #### Debug Log File
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Write all communication to and from the engine into a text file.
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* #### Contempt
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A positive value for contempt favors middle game positions and avoids draws.
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* #### Analysis Contempt
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By default, contempt is set to prefer the side to move. Set this option to "White"
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or "Black" to analyse with contempt for that side, or "Off" to disable contempt.
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* #### Threads
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The number of CPU threads used for searching a position. For best performance, set
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this equal to the number of CPU cores available.
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* #### Hash
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The size of the hash table in MB.
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* #### Clear Hash
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Clear the hash table.
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* #### Ponder
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Let Stockfish ponder its next move while the opponent is thinking.
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* #### MultiPV
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Output the N best lines (principal variations, PVs) when searching.
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Leave at 1 for best performance.
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* #### Skill Level
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Lower the Skill Level in order to make Stockfish play weaker (see also UCI_LimitStrength).
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Internally, MultiPV is enabled, and with a certain probability depending on the Skill Level a
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weaker move will be played.
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* #### UCI_LimitStrength
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Enable weaker play aiming for an Elo rating as set by UCI_Elo. This option overrides Skill Level.
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* #### UCI_Elo
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If enabled by UCI_LimitStrength, aim for an engine strength of the given Elo.
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This Elo rating has been calibrated at a time control of 60s+0.6s and anchored to CCRL 40/4.
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* #### Move Overhead
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Assume a time delay of x ms due to network and GUI overheads. This is useful to
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avoid losses on time in those cases.
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* #### Minimum Thinking Time
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Search for at least x ms per move.
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* #### Slow Mover
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Lower values will make Stockfish take less time in games, higher values will
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make it think longer.
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* #### nodestime
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Tells the engine to use nodes searched instead of wall time to account for
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elapsed time. Useful for engine testing.
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* #### UCI_Chess960
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An option handled by your GUI. If true, Stockfish will play Chess960.
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* #### UCI_AnalyseMode
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An option handled by your GUI.
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* #### SyzygyPath
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Path to the folders/directories storing the Syzygy tablebase files. Multiple
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directories are to be separated by ";" on Windows and by ":" on Unix-based
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operating systems. 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 storing
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the .rtbz files on a regular HD. It is recommended to verify all md5 checksums
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of the downloaded tablebase files (`md5sum -c checksum.md5`) as corruption will
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lead to engine crashes.
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* #### SyzygyProbeDepth
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Minimum remaining search depth for which a position is probed. Set this option
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to a higher value to probe less agressively if you experience too much slowdown
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(in terms of nps) due to TB probing.
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* #### Syzygy50MoveRule
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Disable to let fifty-move rule draws detected by Syzygy tablebase probes count
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as wins or losses. This is useful for ICCF correspondence games.
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* #### SyzygyProbeLimit
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Limit Syzygy tablebase probing to positions with at most this many pieces left
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(including kings and pawns).
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## What to expect from Syzygybases?
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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 153.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 this 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 Stockfish yourself from the sources
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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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## Understanding the code base and participating in the project
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Stockfish's improvement over the last couple of years has been a great
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community effort. There are a few ways to help contribute to its growth.
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### Donating hardware
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Improving Stockfish requires a massive amount of testing. You can donate
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your hardware resources by installing the [Fishtest Worker](https://github.com/glinscott/fishtest/wiki/Running-the-worker)
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and view the current tests on [Fishtest](http://tests.stockfishchess.org/tests).
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### Improving the code
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If you want to help improve the code, there are several valuable ressources:
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* [In this wiki,](https://www.chessprogramming.org) many techniques used in
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Stockfish are explained with a lot of background information.
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* [The section on Stockfish](https://www.chessprogramming.org/Stockfish)
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describes many features and techniques used by Stockfish. However, it is
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generic rather than being focused on Stockfish's precise implementation.
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Nevertheless, a helpful resource.
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* The latest source can always be found on [GitHub](https://github.com/official-stockfish/Stockfish).
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Discussions about Stockfish take place in the [FishCooking](https://groups.google.com/forum/#!forum/fishcooking)
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group and engine testing is done on [Fishtest](http://tests.stockfishchess.org/tests).
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If you want to help improve Stockfish, please read this [guideline](https://github.com/glinscott/fishtest/wiki/Creating-my-first-test)
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first, where the basics of Stockfish development are explained.
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## Terms of use
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Stockfish is free, and distributed under the **GNU General Public License version 3**
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(GPL v3). 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 v3 found in the file named
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*Copying.txt*.
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