Developers

Windows Development Setup

1. https://www.msys2.org/
2. Download the installer

In the MSYS2 Installer change the installation folder to:
C:\tools\msys64

In the URTC64 Shell run:
pacman -S --needed base-devel mingw-w64-ucrt-x86_64-toolchain

Finally rename mingw32-make to make in C:\tools\msys64\ucrt64\bin

clang-format

From https://github.com/llvm/llvm-project/releases/tag/llvmorg-17.0.3 download LLVM-17.0.3-win64.exe

Run the executable and in the installer choose:
Add LLVM to the system PATH for current user

Participating in the project

Stockfish's improvement over the last decade has been a great community effort. Nowadays most development talk takes place on Discord.

There are many ways to contribute to Stockfish:

• Stockfish (C++)
• Fishtest (Python)
• nnue-pytorch (C++ and Python)
• Donating hardware

Stockfish

If you want to contribute to Stockfish directly, you can do so in a couple of ways. Follow the steps described in our Fishtest wiki, and enjoy creating your first test.

New commits to stockfish can mostly be categorised in 2 categories:

Non functional changes

These are changes that don't change the search behaviour and can be directly submitted as pull requests, for example:

• Code cleanups
• Comments
• New commands

Functional changes

These change the search behaviour and lead to a different search tree.
Every functional patch (commit) has to be verified by Fishtest, our testing framework.

NNUE Pytorch

NNUE Pytorch is the trainer for Stockfish's neural network. Usually changes here are tested by training a new network and testing it against the current network via Fishtest.

Donating hardware

Improving Stockfish requires a massive amount of testing. You can donate your hardware resources by installing the Fishtest Worker and view the current tests on Fishtest.

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Git Hooks

Place the following file into .git/hooks/pre-push and make it executable. chmod +x .git/hooks/pre-push. This will prevent you from pushing commits that do not contain a Bench or 'No functional change' in the commit message.

Only really useful for maintainers.

#!/bin/bash

while read local_ref local_sha remote_ref remote_sha; do
    if [[ "$remote_ref" == "refs/heads/master" ]]; then
        # Iterate through commits
        for commit in $(git rev-list --no-merges $remote_sha..$local_sha); do
            # Get the commit message
            commit_msg=$(git log --format=%B -n 1 $commit)

            # Check for the bench regex
            bench_regex='\b[Bb]ench[ :]+[1-9][0-9]{5,7}\b'
            if echo "$commit_msg" | grep -m 1 -o -x -E "$bench_regex" >/dev/null; then
                continue
            fi

            # Check for the "No functional change" regex
            no_functional_change_regex='\b[Nn]o[[:space:]][Ff]unctional[[:space:]][Cc]hange\b'
            if echo "$commit_msg" | grep -o -x -E "$no_functional_change_regex" >/dev/null; then
                continue
            fi

            echo "Commit $commit does not contain a Bench or 'No functional change'"
            exit 1
        done
    fi
done

exit 0

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Using Stockfish in your own project

First of all, you should read our Terms of Use and follow them carefully.

Stockfish is a UCI chess engine, but what does that mean? It means that Stockfish follows the UCI protocol, which you find explained here in great detail. This is the usual way of communicating with Stockfish, so you do not need to write any C++!

Your next step is probably gonna be researching how you can open an executable in your programming language. You will need to write to stdin and listen to stdout, that is where Stockfish's output will end up.

Examples

• Python: https://python-chess.readthedocs.io/en/latest/engine.html
• NodeJS: You can follow this guide on how to communicate with a program.
• C++: You can try out this wrapper for process communication.
• Rust: Examine the documentation on how to spawn a Command.

Limitations

I want Stockfish to comment on the move it made, what do I need to do?

That is not possible. You will have to write your own logic to create such a feature.

I want to get an evaluation of the current position.

While Stockfish has an eval command, it only statically evaluates positions without performing any search. A more precise evaluation is available after you use the go command together with a specified limit.

Other resources

• Commands
• Advanced topics
• Useful data

Terms of use

Stockfish 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. This also means that you can distribute Stockfish alongside your proprietary system, but to do this validly, you must make sure that Stockfish and your program communicate at arm's length, that they are not combined in a way that would make them effectively a single program.

The only real limitation is that whenever you distribute Stockfish 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 GPL v3.