♟️ Chessboard Engine

A chess engine written in C, using bitboards and tested with Criterion.
It can load FEN positions, generate all legal moves, and run perft tests to validate move generation.

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📂 Project Structure

├── assets/           # Resources (images, ...)
├── lib/
│   └── chessboard/   # Engine headers
├── src/
│   └── chessboard/   # Engine source code
├── tests/            # Unit tests (Criterion)
├── Makefile          # Build system
└── README.md         # This file

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⚡ Installation & Build

Requirements

• gcc or clang
• make
• Criterion for tests

  sudo apt-get install libcriterion-dev

Build with GUI

  make ui

Run the engine

  make run

Run tests

  make test

Features

• Load positions via FEN ✅

• Generate all legal moves ✅

• Play a game through a GUI ✅

• Validate move generation using perft tests ✅

• Position evaluation (WIP)

• Search engine (minimax / alpha-beta, WIP)

🧪 CI/CD

This project is automatically tested with GitHub Actions. Unit tests are executed on every push and pull request.

Move generation is validated using perft tests. 👉 Perft results reference

🚀 Optimizations

To improve performance and speed up perft tests, several optimizations have been implemented:

• Bitboards: 64-bit masks to represent the board, enabling fast operations with bitwise logic.

• Precomputed tables: cached attacks for "normal" pieces (knight, pawn, king) and magic bitboards for sliding pieces (rook, bishop, queen).

• Multi-threaded perft: parallelized tree exploration to take advantage of multi-core CPUs.

• Reduced dynamic allocations: use of preallocated arrays (Move move_list[MAX_MOVES]) to avoid unnecessary memory overhead.

⚡ Performance:

Single-thread speed: 8–10 million moves/s

Multi-thread speed: 40–90 million moves/s (⚠️ Multi-threading is less efficient when the root position has fewer legal moves)

Future Work

Planned improvements and features to make the engine stronger and more complete:

Search improvements

• Implement iterative deepening

• Add alpha-beta pruning

• Introduce move ordering (killer moves, history heuristic)

Position evaluation

• Material and piece-square tables

• King safety and pawn structure evaluation

• Mobility and control of the center

Transposition tables

• Store already-evaluated positions using Zobrist hashing

• Reduce redundant calculations in search

UCI Protocol support

• Allow communication with GUIs such as Arena, Cute Chess, or lichess-bot

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📸 Screenshots

🧵 Multi-threaded Perft Test

Exemple d’un perft test lancé en multi-threading :

🎨 Graphical User Interface

Interface graphique permettant de jouer une partie :