[](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).
+derived from Glaurung 2.1. Stockfish is not a complete chess program and requires a
+UCI-compatible graphical user interface (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.
-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.
+The Stockfish engine features two evaluation functions for chess, the classical
+evaluation based on handcrafted terms, and the NNUE evaluation based on efficiently
+updateable neural networks. The classical evaluation runs efficiently on almost all
+CPU architectures, while the NNUE evaluation benefits from the vector
+intrinsics available on most CPUs (sse2, avx2, neon, or similar).
## Files
* 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
+ * a file with the .nnue extension, storing the neural network for the NNUE
+ evaluation. Binary distributions will have this file embedded.
+
+Note: to use the NNUE evaluation, the additional data file with neural network parameters
+needs to be available. Normally, this file is already embedded in the binary or it can be downloaded.
+The filename for the default (recommended) net can be found as the default
+value of the `EvalFile` UCI option, with the format `nn-[SHA256 first 12 digits].nnue`
+(for instance, `nn-c157e0a5755b.nnue`). This file can be downloaded from
```
https://tests.stockfishchess.org/api/nn/[filename]
```
* #### 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).
+ the network parameters must be available to load from file (see also EvalFile),
+ if they are not embedded in the binary.
* #### 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.
+ filename might have to include the full path to the folder/directory that contains the file.
+ Other locations, such as the directory that contains the binary and the working directory,
+ are also searched.
* #### UCI_AnalyseMode
An option handled by your GUI.
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.
* #### Debug Log File
Write all communication to and from the engine into a text file.
-## classical and NNUE evaluation
+## A note on 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
cd src
make help
make build ARCH=x86-64-modern
+ make net
```
When not using the Makefile to compile (for instance with Microsoft MSVC) you
be found by typing the following commands in a console:
```
- ./stockfish
- compiler
+ ./stockfish compiler
```
## Understanding the code base and participating in the project
projects / stockfish / blobdiff