## Overview
-[](https://travis-ci.org/official-stockfish/Stockfish)
+[](https://github.com/official-stockfish/Stockfish/actions)
[](https://ci.appveyor.com/project/mcostalba/stockfish/branch/master)
[Stockfish](https://stockfishchess.org) is a free, powerful UCI chess engine
This distribution of Stockfish consists of the following files:
- * Readme.md, the file you are currently reading.
+ * [Readme.md](https://github.com/official-stockfish/Stockfish/blob/master/README.md), the file you are currently reading.
- * Copying.txt, a text file containing the GNU General Public License version 3.
+ * [Copying.txt](https://github.com/official-stockfish/Stockfish/blob/master/Copying.txt), a text file containing the GNU General Public License version 3.
- * AUTHORS, a text file with the list of authors for the project
+ * [AUTHORS](https://github.com/official-stockfish/Stockfish/blob/master/AUTHORS), a text file with the list of authors for the project
- * src, a subdirectory containing the full source code, including a Makefile
+ * [src](https://github.com/official-stockfish/Stockfish/tree/master/src), a subdirectory containing the full source code, including a Makefile
that can be used to compile Stockfish on Unix-like systems.
* a file with the .nnue extension, storing the neural network for the NNUE
## The UCI protocol and available options
-The Universal Chess Interface (UCI) is a standard protocol used to communicate with a chess engine,
-and is the recommended way to do so for typical graphical user interfaces (GUI) or chess tools.
+The Universal Chess Interface (UCI) is a standard protocol used to communicate with
+a chess engine, and is the recommended way to do so for typical graphical user interfaces
+(GUI) or chess tools. Stockfish implements the majority of it options as described
+in [the UCI protocol](https://www.shredderchess.com/download/div/uci.zip).
-Stockfish implements most commands as described in [the UCI protocol](https://www.shredderchess.com/download/div/uci.zip)
-
-For users, the following UCI options, which can typically be set via a GUI, are available in Stockfish:
+Developers can see the default values for UCI options available in Stockfish by typing
+`./stockfish uci` in a terminal, but the majority of users will typically see them and
+change them via a chess GUI. This is a list of available UCI options in Stockfish:
* #### Threads
The number of CPU threads used for searching a position. For best performance, set
Limit Syzygy tablebase probing to positions with at most this many pieces left
(including kings and pawns).
- * #### 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.
-
* #### 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.
For developers the following non-standard commands might be of interest, mainly useful for debugging:
- * #### bench ttSize threads limit fenFile limitType evalType
- Performs a standard benchmark using various options. The signature or standard node
- count is obtained using all defaults. `bench` is currently `bench 16 1 13 default depth mixed`.
+ * #### bench *ttSize threads limit fenFile limitType evalType*
+ Performs a standard benchmark using various options. The signature of a version (standard node
+ count) is obtained using all defaults. `bench` is currently `bench 16 1 13 default depth mixed`.
* #### compiler
Give information about the compiler and environment used for building a binary.
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
+[The nodchip repository](https://github.com/nodchip/Stockfish) provided the first version of
+the needed tools to train and develop the NNUE networks. Today, more advanced training tools are available
+in [the nnue-pytorch repository](https://github.com/glinscott/nnue-pytorch/), while data generation tools
+are available in [a dedicated branch](https://github.com/official-stockfish/Stockfish/tree/tools).
+
+On CPUs supporting modern vector instructions
(avx2 and similar), the NNUE evaluation results in much stronger playing strength, even
if the nodes per second computed by the engine is somewhat lower (roughly 80% of nps
is typical).
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*.
+[*Copying.txt*](https://github.com/official-stockfish/Stockfish/blob/master/Copying.txt).
projects / stockfish / blobdiff