stockfish_chess_engine

Use Stockfish chess engine in your Flutter project.

This project is based on sources for Stockfish 17.

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);
});

// Create a subscribtion on stderr : subscription that you'll have to cancel before disposing Stockfish.
final stockfishErrorsSubscription = stockfish.stderr.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.
stockfishErrorsSubscription.cancel();
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 ! For that, you can use the chess package.

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

• If testing on IPhone simulator, consider disabling Impeller if the program fails to show UI : flutter run --no-enable-impeller

For stockfish chess engine developpers

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

Changing Stockfish source files

Please, see instructions in file UPGRADING_STOCKFISH.md

Changing the downloaded NNUE file (big or small NNUE)

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(Big or Small), 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.
• Using source code from Flutter Stockfish Plugin