Moonfish Engine (~2000 Elo Rating Lichess.org)

Moonfish is a didactic Python chess engine designed to showcase parallel search algorithms and modern chess programming techniques. Built with code readability as a priority, Moonfish makes advanced concepts easily accessible providing a more approachable alternative to cpp engines.

The engine achieves approximately ~2000 Elo when playing against Lichess Stockfish bots (beats level 5 and loses to level 6) and includes comprehensive test suites including the Bratko-Kopec tactical test positions.

Quickstart

Requirements

• Python 3.10

Installation and usage

Install the python library:

pip install moonfish

From python:

$ python
>>> import chess
>>> import moonfish
>>> board = chess.Board()
>>> moonfish.search_move(board)
Move.from_uci('g1f3')

You can also call the CLI, the CLI works as an UCI Compatible Engine:

$ moonfish --mode=uci
uci # <- user input
id name Moonfish
id author luccabb
uciok

You can also run it as an API:

moonfish --mode=api

Then send a request:

$ curl "http://localhost:5000/?fen=rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR%20w%20KQkq%20-%200%201&depth=4&quiescence_search_depth=3&null_move=True&null_move_r=2&algorithm=alpha_beta"
{
  "body": {
    "move": "e2e4"
  },
  "headers": {
    "Access-Control-Allow-Headers": "Content-Type",
    "Access-Control-Allow-Methods": "OPTIONS,GET",
    "Access-Control-Allow-Origin": "*"
  },
  "statusCode": 200
}

Features

Search Algorithms

• Alpha-Beta Pruning - Negamax with α-β cutoffs
• Lazy SMP - Shared memory parallel search utilizing all CPU cores
• Layer-based Parallelization - Distributing work at specific search depths
• Null Move Pruning - Skip moves to detect zugzwang positions
• Quiescence Search - Extended search for tactical positions

Evaluation & Optimization

• PeSTO Evaluation - Piece-square tables (PST) with tapered evaluation. Using Rofchade's PST.
• Transposition Tables - Caching to avoid redundant calculations
• Move Ordering - MVV-LVA (Most Valuable Victim - Least Valuable Attacker)
• Syzygy Tablebase support for perfect endgame play
• Opening Book integration (Cerebellum format)

Engine Interfaces

• UCI Protocol - Compatible with popular chess GUIs
• Web API - RESTful interface for online integration
• Lichess Bot - Ready for deployment on Lichess.org

Configuration Options

Contributing

We welcome contributions, feel free to open PRs/Issues! Areas of interest:

• New search algorithms
• Improved evaluation functions
• Time constrained search (e.g. find the best move in 40s)
• Additional test positions
• Github CI testing
• Different evaluation functions
• Neural Net integration
• Performance benchmarking on different hardware
• Improving caching

References

• Chess Programming Wiki
• python-chess library
• Lazy SMP Algorithm
• UCI Protocol Specification
• Rofchade
• THE BRATKO-KOPEC TEST RECALIBRATED

License

MIT License - see LICENSE file for details.