GoChessEval

A chess position evaluation backend built with Go and C++, powered by the Stockfish engine. Designed for high-level chess analysis — evaluate any position or compare candidate moves simultaneously using goroutines.

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Tech Stack

• Go — HTTP server and concurrency logic
• Gin — HTTP web framework
• CGo — bridges Go with the C++ Stockfish wrapper
• C++ — native wrapper that communicates with Stockfish via pipes
• Stockfish 17 — the underlying chess engine

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Endpoints

POST /evaluate

Evaluates a single chess position.

Request

{
  "fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
}

Response

{
  "evaluation": "cp 28",
  "bestMove": "e2e4"
}

• evaluation — centipawn score (e.g. cp 28) or forced mate (e.g. mate 3)
• bestMove — best move in UCI notation (e.g. e2e4)

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POST /compare-moves

Evaluates multiple candidate moves from a given position simultaneously using goroutines. Useful for opening preparation and critical position analysis — compare several ideas at once and see which holds up best against Stockfish's response.

Request

{
  "fen": "r1bqkb1r/pp3ppp/2nppn2/8/3NP3/2N1B3/PPP2PPP/R2QKB1R w KQkq - 0 1",
  "moves": ["d4f5", "d4b5", "e4e5"]
}

Response

{
  "results": [
    { "move": "d4f5", "evaluation": "cp 62", "bestResponse": "d6d5" },
    { "move": "d4b5", "evaluation": "cp 45", "bestResponse": "a7a6" },
    { "move": "e4e5", "evaluation": "cp 31", "bestResponse": "f6d5" }
  ]
}

• moves — candidate moves in UCI notation (e.g. e2e4)
• bestResponse — Stockfish's best reply to each candidate move

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Project Structure

chess-backend/
├── main.go                  # Server entry point, route registration
├── analyze.go               # /compare-moves handler and goroutine logic
├── stockfish_wrapper.cpp    # C++ wrapper that communicates with Stockfish via pipes
├── stockfish_wrapper.h      # Header for the C++ wrapper
├── stockfish_wrapper.dll    # Compiled C++ wrapper (Windows)
└── stockfish.exe            # Stockfish 17 binary

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Prerequisites

• Go 1.23+
• MinGW-W64 (GCC/G++ for Windows)
• Stockfish 17 binary placed as stockfish.exe in the project root

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Getting Started

1. Clone the repository

git clone https://github.com/Tristesse02/GoChessEval
cd GoChessEval

2. Install dependencies

go mod tidy

3. Compile the C++ wrapper

g++ -shared -o stockfish_wrapper.dll stockfish_wrapper.cpp -std=c++11 -lws2_32

4. Run the server

go run .

The server starts on http://localhost:8080.

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How Concurrency Works

The /compare-moves endpoint launches one goroutine per candidate move. Each goroutine:

1. Applies the candidate move to the FEN to produce the resulting position
2. Calls Stockfish to evaluate that position

Since the C++ wrapper uses a shared static buffer, a sync.Mutex serializes the Stockfish calls while goroutines handle everything else concurrently. A sync.WaitGroup ensures the handler waits for all evaluations before returning the response.