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Stone-throwing machine 1 Stone-throwing machine ¹

Dabbaba,
a chess playing program by Jens Bæk Nielsen, written from May 1995 to November 1998 in Turbo C to run on PC's under DOS in graphics mode ¹, also able to play chess variants like Knightmate Chess ², Shatranj and many others ³. During its iterative search ⁴ ⁵, maintaining a ply stack of irreversible aspects of the position, that is castling rights, en passant target, halfmove clock, and hash-keys, it updates its mailbox board and piece-lists incrementally during make and unmake move. A feature of Dabbaba is that it starts its search by using up to 20% of the allotted time for a move using a mate search at depth zero, following long sequences of checks to see if it results in a mate, material gain or perhaps a saving draw. To avoid a search explosion, Dabbaba considers ply-distance to the root and number of replies so that shallow lines are searched deeper than wide lines ⁶. In May 2008, Jim Ablett released a WinBoard version of Dabbaba ⁷, and in August 2012, Jens Bæk Nielsen as well ⁸.

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Etymology

The Dabbaba (or dabaaba, dabbabah) is a Fairy chess piece that jumps two squares orthogonally, leaping over intermediate pieces like a knight, also called (2,0)-leaper. The Arabic word dabbāba formerly meant a type of medieval siege engine, and nowadays an army tank.

Dabbaba Screen ⁹