--- /dev/null
+## Overview
+
+[](https://travis-ci.org/official-stockfish/Stockfish)
+[](https://ci.appveyor.com/project/mcostalba/stockfish/branch/master)
+
+[Stockfish](https://stockfishchess.org) is a free, powerful UCI chess engine
+derived from Glaurung 2.1. It features two evaluation functions, the classical
+evaluation based on handcrafted terms, and the NNUE evaluation based on
+efficiently updateable neural networks. The classical evaluation runs efficiently
+on most 64bit CPU architectures, while the NNUE evaluation benefits strongly from the
+vector intrinsics available on modern CPUs (avx2 or similar).
+
+Stockfish is not a complete chess program and requires a
+UCI-compatible GUI (e.g. XBoard with PolyGlot, Scid, Cute Chess, 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.
+
+
+## Files
+
+This distribution of Stockfish consists of the following files:
+
+ * Readme.md, the file you are currently reading.
+
+ * Copying.txt, a text file containing the GNU General Public License version 3.
+
+ * src, a subdirectory containing the full source code, including a Makefile
+ that can be used to compile Stockfish on Unix-like systems.
+
+To use the NNUE evaluation an additional data file with neural network parameters
+needs to be downloaded. The filename for the default set can be found as the default
+value of the `EvalFile` UCI option, with the format
+`nn-[SHA256 first 12 digits].nnue` (e.g. nn-c157e0a5755b.nnue). This file can be downloaded from
+```
+https://tests.stockfishchess.org/api/nn/[filename]
+```
+replacing `[filename]` as needed.
+
+
+## UCI options
+
+Currently, Stockfish has the following UCI options:
+
+ * #### Threads
+ The number of CPU threads used for searching a position. For best performance, set
+ this equal to the number of CPU cores available.
+
+ * #### Hash
+ The size of the hash table in MB. It is recommended to set Hash after setting Threads.
+
+ * #### Ponder
+ Let Stockfish ponder its next move while the opponent is thinking.
+
+ * #### MultiPV
+ Output the N best lines (principal variations, PVs) when searching.
+ Leave at 1 for best performance.
+
+ * #### Use NNUE
+ Toggle between the NNUE and classical evaluation functions. If set to "true",
+ the network parameters must be availabe to load from file (see also EvalFile).
+
+ * #### EvalFile
+ The name of the file of the NNUE evaluation parameters. Depending on the GUI the
+ filename should include the full path to the folder/directory that contains the file.
+
+ * #### Contempt
+ A positive value for contempt favors middle game positions and avoids draws,
+ effective for the classical evaluation only.
+
+ * #### Analysis Contempt
+ By default, contempt is set to prefer the side to move. Set this option to "White"
+ or "Black" to analyse with contempt for that side, or "Off" to disable contempt.
+
+ * #### UCI_AnalyseMode
+ An option handled by your GUI.
+
+ * #### UCI_Chess960
+ An option handled by your GUI. If true, Stockfish will play Chess960.
+
+ * #### UCI_ShowWDL
+ If enabled, show approximate WDL statistics as part of the engine output.
+ These WDL numbers model expected game outcomes for a given evaluation and
+ game ply for engine self-play at fishtest LTC conditions (60+0.6s per game).
+
+ * #### UCI_LimitStrength
+ Enable weaker play aiming for an Elo rating as set by UCI_Elo. This option overrides Skill Level.
+
+ * #### UCI_Elo
+ If enabled by UCI_LimitStrength, aim for an engine strength of the given Elo.
+ This Elo rating has been calibrated at a time control of 60s+0.6s and anchored to CCRL 40/4.
+
+ * #### Skill Level
+ Lower the Skill Level in order to make Stockfish play weaker (see also UCI_LimitStrength).
+ Internally, MultiPV is enabled, and with a certain probability depending on the Skill Level a
+ weaker move will be played.
+
+ * #### SyzygyPath
+ Path to the folders/directories storing the Syzygy tablebase files. Multiple
+ directories are to be separated by ";" on Windows and by ":" on Unix-based
+ operating systems. Do not use spaces around the ";" or ":".
+
+ Example: `C:\tablebases\wdl345;C:\tablebases\wdl6;D:\tablebases\dtz345;D:\tablebases\dtz6`
+
+ It is recommended to store .rtbw files on an SSD. There is no loss in storing
+ the .rtbz files on a regular HD. It is recommended to verify all md5 checksums
+ of the downloaded tablebase files (`md5sum -c checksum.md5`) as corruption will
+ lead to engine crashes.
+
+ * #### SyzygyProbeDepth
+ Minimum remaining search depth for which a position is probed. Set this option
+ to a higher value to probe less agressively if you experience too much slowdown
+ (in terms of nps) due to TB probing.
+
+ * #### Syzygy50MoveRule
+ Disable to let fifty-move rule draws detected by Syzygy tablebase probes count
+ as wins or losses. This is useful for ICCF correspondence games.
+
+ * #### SyzygyProbeLimit
+ Limit Syzygy tablebase probing to positions with at most this many pieces left
+ (including kings and pawns).
+
+ * #### Move Overhead
+ Assume a time delay of x ms due to network and GUI overheads. This is useful to
+ avoid losses on time in those cases.
+
+ * #### Slow Mover
+ Lower values will make Stockfish take less time in games, higher values will
+ make it think longer.
+
+ * #### nodestime
+ Tells the engine to use nodes searched instead of wall time to account for
+ elapsed time. Useful for engine testing.
+
+ * #### Clear Hash
+ Clear the hash table.
+
+ * #### Debug Log File
+ Write all communication to and from the engine into a text file.
+
+## classical and NNUE evaluation
+
+Both approaches assign a value to a position that is used in alpha-beta (PVS) search
+to find the best move. The classical evaluation computes this value as a function
+of various chess concepts, handcrafted by experts, tested and tuned using fishtest.
+The NNUE evaluation computes this value with a neural network based on basic
+inputs (e.g. piece positions only). The network is optimized and trained
+on the evalutions of millions of positions at moderate search depth.
+
+The NNUE evaluation was first introduced in shogi, and ported to Stockfish afterward.
+It can be evaluated efficiently on CPUs, and exploits the fact that only parts
+of the neural network need to be updated after a typical chess move.
+[The nodchip repository](https://github.com/nodchip/Stockfish) provides additional
+tools to train and develop the NNUE networks.
+
+On CPUs supporting modern vector instructions (avx2 and similar), the NNUE evaluation
+results in stronger playing strength, even if the nodes per second computed by the engine
+is somewhat lower (roughly 60% of nps is typical).
+
+Note that the NNUE evaluation depends on the Stockfish binary and the network parameter
+file (see EvalFile). Not every parameter file is compatible with a given Stockfish binary.
+The default value of the EvalFile UCI option is the name of a network that is guaranteed
+to be compatible with that binary.
+
+## What to expect from Syzygybases?
+
+If the engine is searching a position that is not in the tablebases (e.g.
+a position with 8 pieces), it will access the tablebases during the search.
+If the engine reports a very large score (typically 153.xx), this means
+that it has found a winning line into a tablebase position.
+
+If the engine is given a position to search that is in the tablebases, it
+will use the tablebases at the beginning of the search to preselect all
+good moves, i.e. all moves that preserve the win or preserve the draw while
+taking into account the 50-move rule.
+It will then perform a search only on those moves. **The engine will not move
+immediately**, unless there is only a single good move. **The engine likely
+will not report a mate score even if the position is known to be won.**
+
+It is therefore clear that this behaviour is not identical to what one might
+be used to with Nalimov tablebases. There are technical reasons for this
+difference, the main technical reason being that Nalimov tablebases use the
+DTM metric (distance-to-mate), while Syzygybases use a variation of the
+DTZ metric (distance-to-zero, zero meaning any move that resets the 50-move
+counter). This special metric is one of the reasons that Syzygybases are
+more compact than Nalimov tablebases, while still storing all information
+needed for optimal play and in addition being able to take into account
+the 50-move rule.
+
+## Large Pages
+
+Stockfish supports large pages on Linux and Windows. Large pages make
+the hash access more efficient, improving the engine speed, especially
+on large hash sizes. Typical increases are 5..10% in terms of nps, but
+speed increases up to 30% have been measured. The support is
+automatic. Stockfish attempts to use large pages when available and
+will fall back to regular memory allocation when this is not the case.
+
+### Support on Linux
+
+Large page support on Linux is obtained by the Linux kernel
+transparent huge pages functionality. Typically, transparent huge pages
+are already enabled and no configuration is needed.
+
+### Support on Windows
+
+The use of large pages requires "Lock Pages in Memory" privilege. See
+[Enable the Lock Pages in Memory Option (Windows)](https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/enable-the-lock-pages-in-memory-option-windows)
+on how to enable this privilege. Logout/login may be needed
+afterwards. Due to memory fragmentation, it may not always be
+possible to allocate large pages even when enabled. A reboot
+might alleviate this problem. To determine whether large pages
+are in use, see the engine log.
+
+## Compiling Stockfish yourself from the sources
+
+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.
+
+```
+ cd src
+ make help
+ make build ARCH=x86-64-modern
+```
+
+When not using the 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.
+
+When reporting an issue or a bug, please tell us which version and
+compiler you used to create your executable. These informations can
+be found by typing the following commands in a console:
+
+```
+ ./stockfish
+ compiler
+```
+
+## Understanding the code base and participating in the project
+
+Stockfish's improvement over the last couple of years has been a great
+community effort. There are a few ways to help contribute to its growth.
+
+### Donating hardware
+
+Improving Stockfish requires a massive amount of testing. You can donate
+your hardware resources by installing the [Fishtest Worker](https://github.com/glinscott/fishtest/wiki/Running-the-worker:-overview)
+and view the current tests on [Fishtest](https://tests.stockfishchess.org/tests).
+
+### Improving the code
+
+If you want to help improve the code, there are several valuable resources:
+
+* [In this wiki,](https://www.chessprogramming.org) many techniques used in
+Stockfish are explained with a lot of background information.
+
+* [The section on Stockfish](https://www.chessprogramming.org/Stockfish)
+describes many features and techniques used by Stockfish. However, it is
+generic rather than being focused on Stockfish's precise implementation.
+Nevertheless, a helpful resource.
+
+* The latest source can always be found on [GitHub](https://github.com/official-stockfish/Stockfish).
+Discussions about Stockfish take place in the [FishCooking](https://groups.google.com/forum/#!forum/fishcooking)
+group and engine testing is done on [Fishtest](https://tests.stockfishchess.org/tests).
+If you want to help improve Stockfish, please read this [guideline](https://github.com/glinscott/fishtest/wiki/Creating-my-first-test)
+first, where the basics of Stockfish development are explained.
+
+
+## Terms of use
+
+Stockfish is free, and distributed under the **GNU General Public License version 3**
+(GPL v3). 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 v3 found in the file named
+*Copying.txt*.
projects / stockfish / blobdiff