Boomchess

WIP Atomic chess engine written in C++

Reaches depths of around 10 in under 5s.

Supports UCI and NNUE

Around 1.1M (18M for perft) Nodes per second on i7-8750H. (Compiled with -O3)

Features

Board:

• 0x88 representation
• Optimized with piece lists
• Incremental move make and unmake
• Incremental Zobrist hashing

Search:

• Negamax with alpha beta pruning
• Transposition table
• Iterative deepening
• Principal variation search
• Quiescence search
• Null move heuristic
• Move ordering:
  • Best move from transposition table
  • MVV-LVA
  • Killer heuristic
  • History heuristic

NNUE:

• (768 -> 128) * 2 -> 32 -> 32 -> 1 network
• Close to 300 elo stronger than HCE
• Trained on self-made dataset of 3.6M D8 positions
• Networks and and training code can be found here (D8_FULL.nnue is the strongest)
• Enabled by UCI option NNUEPath

Hand crafted evaluation:

• Material
• Piece-square tables
• Mobility
• Protected pieces (capturing would loose opponent material from explosion)
• King safety
  • penalty for pieces attacking kings radius
  • small penalty for friendly pieces touching king
  • touching kings

P.S. The code neeeds heavy refactoring