stockfish_chess_engine 0.1.0

Use Stockfish chess engine in your Flutter project.

stockfish_chess_engine

Use Stockfish chess engine in your Flutter project.

This project is based on sources for Stockfish 15.

Usage

final stockfish = new Stockfish()

// Create a subscribtion on stdout : subscription that you'll have to cancel before disposing Stockfish.
final stockfishSubscription = stockfish.stdout.listen((message) {
    print(message);
});

// Get Stockfish ready
stockfish.stdin = 'isready'

// Send you commands to Stockfish stdin
stockfish.stdin = 'position startpos' // set up start position
stockfish.stdin = 'position fen rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2' // set up custom position
stockfish.stdin = 'go movetime 1500' // search move for at most 1500ms

// Don't remember to dispose Stockfish when you're done.
stockfishSubscription.cancel();
stockfish.dispose();

You can see an example usage in example folder.

Important notes

• You must check the position validity before sending it to stdin, otherwise program will crash on illegal position ! And using chess.js is not enough, as it does not check for kings count validity or kings not touching each other, nor the fact that no pawn can be on first/last rank. (As a temporary solution, you can use package chess_loloof64).

• As the library creates two isolates, you must dispose Stockfish before perfoming an hot reload / hot restart, and then creating a new Stockfish instance.

Limitation

• You should not use Stockfish package if you're also using a logger package. Logging messages to the console may break the Stockfish package functionality.

For stockfish chess engine developpers

1. Run flutter pub get.
2. Uncomment line #define _ffigen on top of src/stockfish.h (for the ffi generation to pass).
3. Run command flutter pub run ffigen --config ffigen.yaml. More on https://pub.dev/packages/ffigen for the prerequesites per OS.
4. Comment line #define _ffigen in src/stockfish.h (otherwise Stockfish engine compilation will pass but be incorrect).

Changing the downloaded NNUE file

1. Go to Stockfish NNUE files page and select a reference from the list.
2. Modify CMakeLists.txt, by replacing lines starting by set (NNUE_NAME ) by setting your reference name, without any quote.
3. Modify the reference name in evaluate.h in the line containing #define EvalFileDefaultName , by setting your nnue file name, with the quotes of course.
4. Don't forget to clean project before building again (flutter clean then flutter pub get).

Credits

• Using source code from Stockfish.
• Using source code from Flutter Stockfish.