bunnies

A fast chess library for chess engines. Currently in alpha.

Current Features

• Game state representation
• Legal move generation
• Forwards-backwards move application
• FEN parsing and generation
• UCI generation
• Full PGN parsing and generation
  • Support for NAGs and variations (comments are parsed, but not generated)
  • Support for nested variations
• Perft tests
• Game termination detection (and draw detection)

Optimizations

bunnies makes use of the following optimizations:

• Bitboard-based board representation
• Direct legal move generation that takes pins and checks into account (no pseudolegal step and validation)
• Make-unmake move application (eliminating the need to copy game state during search)
• Magic bitboards for sliding piece attack generation
• Precomputed attacks for knights and kings
• Zobrist hashing for board state hashing

bunnies is currently able to generate ~23M moves/thread/second (as measured on an M1 Macbook Pro), which is not nearly as fast as programs like Stockfish (which is able to generate ~120M moves/thread/sec under the same conditions).

Contribution

bunnies needs the following to make 1.0.0 happen:

• Multithreading
• Further performance improvement
  • Figure out bottlenecks
  • Solve inefficiencies
• More tests wouldn't hurt
• More benchmarks wouldn't hurt
• Support for PGN comments

Feedback and contributions welcome!