Sand

The first word it came to my mind and a chess engine

A UCI-compliant chess engine in the alpha-beta framework and a major source of pain to my life. I failed spectacularly did my best to keep the source code elegant and idiomatic while maintaining good performance on the critical paths (I wasn't coding drunk, I swear).

Features

Board representation

• Bitboards
• Fancy magic bitboards
• 8x8 board (for fast look-up)

Search

• PVS
• Iterative deepening
• Quiescence
• Transposition table
• Move ordering:
  • TT-move first
  • PV-move first
  • MVV/LVA
  • Killer heuristic
  • History heuristics
    • Gravity formula
    • History maluses
• Selectivity:
  • SEE pruning (quiescence only)
  • Mate distance pruning
  • Delta pruning

Evaluation

• Material
• Piece-Square tables (stolen borrowed from PesTO)
• Tapered evaluation

Build

cargo build --bin sand --release

Specify the --bin because it also has other binaries (like perft_test and find_magics).

Usage

• To run the engine, go to target/release and run ./sand.
• To run a perft test you compile with --bin perft_test and run ./target/release/perft_test <epd test suite> <depth> <hash table size in mb>
• To recompute the magics (if you dare) just run cargo r --bin find_magics -r and copy-paste to the file src/chess/attacks/magics.rs

UCI Compatibility

Supports

• All basic UCI commands (uci, isready, position, go wtime ..., etc).
• Pondering

Unsupported

• go mate and go nodes
• Options

Known issues

• Might lose to Stockfish in 0.5 seconds.
• Sometimes hallucinates illegal moves when sleep-deprived.

Performance

On my overpowered Intel Pentium Silver N5030 it achieves:

• 9M-24M N/s on perft depth 5 (depending on CPU usage and hash size).
• 1.5 M N/s on average during search.

ELO

Sand was tested against Maia 1500 at blitz time control (tc=60+0.5) over 400 games (200 as White, 200 as Black) using the Unbalanced Human Openings (UHO 2022).

• Observed draw rate: ~10.5% (anti-draw openings).
• Sand scored 1857 ± 33 ELO assuming Maia is exactly 1500 at this time control.

License

Sand is currently under the MIT license. However, I'm developing the "I don't fucking care" license, which allows you to do whatever you want with the source code.