A toy chess playing program using minimax with bitmaps, alpha-beta pruning and transpositions detection.

prawn understands FEN game notation, moves in long algebraic notation, and it's own format of simple opening books. It has a text interface, with which it supports self-play and playing versus human players, plus it supports external graphical user intrfaces via the UCI chess protocol.

For regression testing, playing against other versions of itself, a separate tool called bait is available:

./bait "./prawn-test"  "./prawn-baseline"

bait is tailored specifically for prawn, and prawn is currently deterministic, meaning two versions playing against each other, repeatedly, will always arrive at the same result. The only exception is when using the opening book. This means that when regression testing with the opening book enabled, it is never necessary to run it for longer than the leaf variety of the opening book.

Because of this, prawn can be asked to convert the opening book into a list of positions in FEN format, and bait can then be asked to cycle through all positions, two games for each (alternating colors), instead of randomly picking new openings every time.

To do this run

./prawn --convert-ob-at=4 > bait.input

./bait "./prawn-test" "./prawn-baseline" --collection=bait.input

Regression testing from a given collection automatically disables the openings book.