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Woodpusher mascot

a chess program developed in 1989 by John Hamlen as part of a university project looking into null-move search techniques. Woodpusher played various World Computer-, World Microcomputer Chess Championships and Computer Olympiads. Woodpusher 1997 played the WCCC 2004 in Ramat-Gan and the WCCC 2011 in Tilburg as an experiment to play with a seven respectively fourteen years old program.


Description given in 1995 from the ICGA tournament site [1] :

Woodpusher is a small chess program (< 64K) of conventional design. It uses an iterative deepening alpha-beta search with PVS and aspiration window enhancements. The first version of Woodpusher was born in 1989 as part of a university project looking into null-move search techniques. True to it's origins, this new version of the program still uses the null-move throughout the search to recognize threats and to forward prune branches of the search tree. A database of attacks from and to all the squares on the board is maintained by using CHESS 4.5's bit-board implementation. These data structures are used for both generating moves and making positional evaluations. Woodpusher's position evaluation is maintained almost entirely incrementally while making and un-making moves during the search, with very little work done at the terminal nodes. The evaluation is therefore necessarily simple, but does include true measures of mobility rather than relying on piece-square evaluations. 



WCCC 2011, Woodpusher 1997 by John Hamlen vs. Pandix by Gyula Horváth (left) [2]


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