sunfish/sunfish.py at master · thomasahle/sunfish

Abstraction: Minimalist 500-line Python chess engine using MTD-bi search

Key points:

• Board represented as 120-character padded string; padding enables fast out-of-bounds detection
• Piece-square tables (PST) encode positional value for all 6 piece types; Pawn=100, Queen=929, King=60000
• Search uses iterative deepening MTD-bi (binary search on score) with transposition table
• Implements null-move pruning, quiescent search, internal iterative deepening (IID), and futility pruning
• Stochastic gradient descent-style stalemate handling: checks if king is capturable at depth 0
• UCI protocol compatible; designed to run under PyPy for performance

Connections: Sunfish · Github · Game Tree Search · Minimax · Iterative Deepening

Source: https://github.com/thomasahle/sunfish/blob/master/sunfish.py