woodpusher

(chess, informal, derogatory) A bad player; an amateur.

A more or less UCI-compatible chess engine. Plug it into your favourite GUI.

Features

• UCI-compatible
• PGN and FEN parsing
• Perft test
• Opening book
• Zobrist hashing
• Negamax search with alpha-beta pruning
  • NegaScout (or PVS?)
  • Quiescence
  • Iterative deepening
  • Null move pruning
  • Move ordering
    • MVV/LVA, history heuristic, killer heuristic, transposition table

UCI Commands

uci

Initializes the engine and provides engine information.

Arguments:

• None

Example:

uci
id name Woodpusher 1.6.0+eadfe77ee3e88bf7fbd97491bcdf15d3f09b07a5
id author Mikael Fredriksson <micke@sictransit.net>
option name OwnBook type check default true
option name Ponder type check default false
uciok

setoption

Sets an engine option.

Arguments:

• name <option_name>: The name of the option.
• value <option_value>: The value of the option.

Example:

setoption name OwnBook value false

The engine will ignore the ponder option. It is not implemented fully implemented yet.

isready

Checks if the engine is ready.

Arguments:

• None

ucinewgame

Initializes a new game.

Arguments:

• None

position

Sets up the board position using FEN and optional moves.

Arguments:

• fen <fen_string>: Sets the board position using the provided FEN string.
• moves <move1> <move2> ...: A list of moves in algebraic notation to be played from the given position or the starting position if no FEN is provided.

Example:

position fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 moves e2e4 e7e5

go

Starts the engine to find the best move or perform a perft test.

Arguments:

• wtime <milliseconds>: White's remaining time in milliseconds.
• btime <milliseconds>: Black's remaining time in milliseconds.
• movestogo <number>: Number of moves to the next time control.
• movetime <milliseconds>: Time to search in milliseconds.
• perft <depth>: Perform a perft test to the given depth.

Example:

go wtime 300000 btime 300000 movestogo 40
info string debug playing opening book g1f3
bestmove g1f3

stop

Stops the engine's current calculation.

Arguments:

• None

d

Displays the current board position.

Arguments:

• None

Example:

d
8 r n b q k b n r
7 p p p p · p p p
6 · · · · · · · ·
5 · · · · p · · ·
4 · · · · P · · ·
3 · · · · · · · ·
2 P P P P · P P P
1 R N B Q K B N R
  a b c d e f g h
Hash: 6805972066694293741
FEN: rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq e6 0 2

quit

Exits the engine.

Arguments:

• None

Strength of play (ELO)

On my machine it plays about even vs Stockfish 15 locked to ELO 2500. It is not a fair comparison since Stockfish seems to blunder to lower its strength, but it is a number.