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  [![Build][build-badge]][build-link]
  [![License][license-badge]][license-link]
  <br>
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  [![Commits][commits-badge]][commits-link]
  <br>
  [![Website][website-badge]][website-link]
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## Overview

[Pikafish][website-link] is a free, powerful UCI xiangqi engine derived from
Stockfish. Pikafish is not a complete xiangqi program and requires a UCI-compatible
graphical user interface (GUI) (e.g. VinXiangQi or BHGUI) in order to be used comfortably.
Read the documentation for your GUI of choice for information about how to use
Pikafish with it.

The Pikafish engine features the efficiently updatable neural network (NNUE) based
evaluation for xiangqi, which is by far the strongest. The strongest network can be 
downloaded from our official website. The NNUE evaluation benefits from the vector 
intrinsics available on most CPUs (sse2, avx2, neon, or similar).

## Files

This distribution of Pikafish consists of the following files:

  * [README.md][readme-link], the file you are currently reading.

  * [Copying.txt][license-link], a text file containing the GNU General Public License
    version 3.

  * [AUTHORS][authors-link], a text file with the list of authors for the official Pikafish project.

  * [src][src-link], a subdirectory containing the full source code, including a Makefile
    that can be used to compile Pikafish on Unix-like systems.

## 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. Pikafish implements the majority of its options as described
in [the UCI protocol][uci-link].

Developers can see the default values for UCI options available in Pikafish by typing
`./pikafish 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 Pikafish:

  * #### 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.

  * #### Clear Hash
    Clear the hash table.

  * #### Ponder
    Let Pikafish 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.

  * #### EvalFile
    The name of the file of the NNUE evaluation parameters. Depending on the GUI the
    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.

  * #### 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).

  * #### 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 Pikafish 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.

  * #### Debug Log File
    Write all communication to and from the engine into a text file.

For developers the following non-standard commands might be of interest, mainly useful for debugging:

  * #### bench *ttSize threads limit fenFile limitType*
    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`.

  * #### compiler
    Give information about the compiler and environment used for building a binary.

  * #### d
    Display the current position, with ascii art and fen.

  * #### eval
    Return the evaluation of the current position.

  * #### export_net [filename]
    Exports the currently loaded network to a file.
    If the currently loaded network is the embedded network and the filename
    is not specified then the network is saved to the file matching the name
    of the embedded network, as defined in evaluate.h.
    The filename parameter is required and the network is saved into that file.

  * #### flip
    Flips the side to move.


## A note on NNUE evaluation

This approach assigns a value to a position that is used in alpha-beta (PVS) search
to find the best move. 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 evaluations 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][nodchip-link] 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][pytorch-link], while data generation tools
are available in [a dedicated branch][tools-link].

We change the feature sets and port the HalfKAv2_hm structure to xiangqi 
and rename it as HalfKAv2_xq.

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).

Notes:

1) the NNUE evaluation depends on the Pikafish binary and the network parameter file 
(see the EvalFile UCI option). Not every parameter file is compatible with a given
Pikafish binary, but the default value of the EvalFile UCI option is the name of a 
network that is guaranteed to be compatible with that binary.

2) to use the NNUE evaluation, the additional data file with neural network parameters
needs to be available. The filename for the default (recommended) net can be found as 
the default value of the `EvalFile` UCI option, with the format `pikafish.nnue`. 
This file can be downloaded from `http://test.pikafish.org`.

## Large Pages

Pikafish 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 nodes per
second, but speed increases up to 30% have been measured. The support is
automatic. Pikafish 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)][lockpages-link]
on how to enable this privilege, then run [RAMMap][rammap-link]
to double-check that large pages are used. We suggest that you reboot
your computer after you have enabled large pages, because long Windows
sessions suffer from memory fragmentation, which may prevent Stockfish
from getting large pages: a fresh session is better in this regard.

## Compiling Pikafish yourself from the sources

Pikafish 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 Pikafish
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 Pikafish version
and which compiler you used to create your executable. This information
can be found by typing the following command in a console:

```
    ./pikafish compiler
```

## Understanding the code base and participating in the project

Pikafish's improvement over the last decade has been a great community
effort. There are a few ways to help contribute to its growth.

### Donating hardware

Improving Pikafish requires a massive amount of testing. You can donate
your hardware resources by installing the [Fishtest Worker][worker-link]
and view the current tests on [Fishtest][fishtest-link].

### Improving the code

If you want to help improve the code, there are several valuable resources:

* [In this wiki,][programming-link] many techniques used in
Pikafish are explained with a lot of background information.

* [The section on Stockfish][programmingsf-link]
describes many features and techniques used by Pikafish. 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][github-link].
Discussions about Pikafish take place these days mainly in the 
[Pikafish 分布式训练 / Vin象棋连线][qqgroup-link] QQ group.
The engine testing is done on [Fishtest][fishtest-link].
If you want to help improve Pikafish, please read this [guideline][guideline-link]
first, where the basics of Pikafish development are explained.


## Terms of use

Pikafish is free, and distributed under the **GNU General Public License version 3**
(GPL v3). Essentially, this means 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 website, 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 Pikafish in
some way, you MUST always include the license and the full source code
(or a pointer to where the source code can be found) to generate the 
exact binary you are distributing. If you make any changes to the
source code, these changes must also be made available under the GPL v3.

For full details, read the copy of the GPL v3 found in the file named
[*Copying.txt*][license-link].


## Goal of the project
The current goal of the project is to make Pikafish suppress all commercial engines and become the top 1. Terminating the domination of those commercial engines like AlphaCat, BugChess, and Cyclone in xiangqi. Making the strongest xiangqi engine free and open source to everyone.

I believe if Stockfish can do that for chess, Pikafish can do that for xiangqi.


## Hall of shame

The following individuals and organizations are prohibited from using the nnue 
weights file derived from this program due to their unfriendly actions, activities, and 
license violations（鉴于近期出现的种种不友好的行为，以下个人和组织将被禁止使用由本程序引申出的所有 nnue 权重文件）：
+ AlanThinker (鹏飞象棋)
+ 国圣
+ 飞风追云

[authors-link]:https://github.com/PikaCat-OuO/Pikafish/blob/master/AUTHORS
[build-badge]:https://img.shields.io/github/workflow/status/PikaCat-OuO/Pikafish/Pikafish?style=for-the-badge&label=pikafish&logo=github
[build-link]:https://github.com/PikaCat-OuO/Pikafish/actions/workflows/pikafish.yml
[commits-badge]:https://img.shields.io/github/commits-since/PikaCat-OuO/Pikafish/latest?style=for-the-badge
[commits-link]:https://github.com/PikaCat-OuO/Pikafish/commits/master
[discord-badge]:https://img.shields.io/discord/1013130558089478144?style=for-the-badge&label=discord&logo=Discord
[discord-link]:https://discord.com/invite/uSb3RXb7cY
[qqgroup-link]:https://jq.qq.com/?_wv=1027&k=FORWUh4W
[fishtest-badge]:https://img.shields.io/website?style=for-the-badge&down_color=red&down_message=Offline&label=Fishtest&up_color=success&up_message=Online&url=https://test.pikafish.org
[fishtest-link]:https://test.pikafish.org
[github-link]:https://github.com/PikaCat-OuO/Pikafish
[guideline-link]:https://github.com/glinscott/fishtest/wiki/Creating-my-first-test
[license-badge]:https://img.shields.io/github/license/PikaCat-OuO/Pikafish?style=for-the-badge&label=license&color=success
[license-link]:https://github.com/PikaCat-OuO/Pikafish/blob/master/Copying.txt
[lockpages-link]:https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/enable-the-lock-pages-in-memory-option-windows
[nodchip-link]:https://github.com/nodchip/Stockfish
[programming-link]:https://www.chessprogramming.org/Main_Page
[programmingsf-link]:https://www.chessprogramming.org/Stockfish
[pytorch-link]:https://github.com/glinscott/nnue-pytorch
[rammap-link]:https://docs.microsoft.com/en-us/sysinternals/downloads/rammap
[readme-link]:https://github.com/PikaCat-OuO/Pikafish/blob/master/README.md
[release-badge]:https://img.shields.io/github/v/release/PikaCat-OuO/Pikafish?style=for-the-badge&label=official%20release
[release-link]:https://github.com/PikaCat-OuO/Pikafish/releases/latest
[src-link]:https://github.com/PikaCat-OuO/Pikafish/tree/master/src
[tools-link]:https://github.com/PikaCat-OuO/Pikafish/tree/tools
[uci-link]:https://www.shredderchess.com/download/div/uci.zip
[website-badge]:https://img.shields.io/website?style=for-the-badge&down_color=red&down_message=Offline&label=website&up_color=success&up_message=Online&url=https://pikafish.org
[website-link]:https://pikafish.org
[worker-link]:https://github.com/xyztnecniV/yolo