Stef Keetman

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Stef Keetman [1]

Stef Keetman,
a Dutch computer scientist, Draughts programmer and software developer in the systematic trading field, where he applies techniques of AI. He holds a M.Sc. in computer science from the University of Amsterdam [2].


During the late 80s and early 90s, while affiliated with the University of Limburg and its upcoming Games and AI Group headed by Jaap van den Herik, also as Draughts player [3], he wrote the Draughts program Truus [4] [5], winner of the Silver medal at the 1st Computer Olympiad, London 1989, and the Gold medal at the 3rd Computer Olympiad, Maastricht 1991. Along with Ard van Bergen, he developed the Draughts engine for Oxford Softworks' Intelligent Strategy Games 10 [6].

Improving Chinook

During his half year sabbatical in Maastricht in early 1994 with the aim to prepare and improve his Checkers player Chinook for the 2nd upcoming Tinsley match, Jonathan Schaeffer worked along with Stef Keetman to profit from some of his ideas implemented in Truus. One of Truus' novel features was the extensive use of tactical patterns in the evaluation function, and its ability to learn Draughts tactics. When Truus found a forced sequence of moves that won a checker, the program would remember the conditions necessary for the sequence to work. The so called two-for-one pattern, where a sacrifice of a checker due to the mandatory capture allows recapturing two or more checkers by successive jumps, was adapted to Chinook. Many conditions and exceptions had to be considered which was quite error prone - therefore the possible inexact pattern match was not used in evaluation, but to trigger an extension, improving Chinook's strength considerably [7].

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