Boychesser

A very small C# chess engine written for Sebastian Lague's Tiny Chess Bots Challenge. Estimated to be around 2750 Elo on the CCRL Blitz list.

Features

Board representation

• Based entirely on Sebastian Lague's framework

Search

• Principal variation search
• Quiescence search (integrated with main search)
• Transposition table
• Aspiration windows
• Pruning
  • Null move pruning
  • Reverse futility pruning
  • Delta pruning
  • Futility pruning
  • Late move pruning
• Reductions
  • Late move reduction
  • History reduction
  • Internal iterative reduction
• Extensions
  • Check extension
• Move ordering
  • TT move
  • MVV-LVA
  • History heuristic (with gravity)

Evaluation

• Phased evaluation
• Material
• Mirrored piece square tables
• King-relative pawn
• Slider mobility
• Virtual queen mobility
• Friendly pawns in front of a piece
• Tempo
• Tuned on an evenly-mixed combination of Frozenight NNUE data and lichess-big3-resolved

Time management

• Based on a fixed percentage of remaining time
• Aborts after an iteration if a "soft" limit is exceeded
• Aborts during an iteration if a "hard" limit is exceeded