14 - Game Playing

Summary

I have already mentioned attempts to program computers to play borad games, such as chess and checkers. The most successful of these was Arthur Samuel's checker-playing program. In 1967, Samuel published a paper describing an improved version of his program. He had refined the program's search procedure and incorporated better “book-learning” capabilities, and instead of calculating the estimated value of a position by adding up weighted feature values, he used hierarchically organized tables. According to Richard Sutton, “This version learned to play much better than the 1959 program, though still not at a master level.”

Between 1959 and 1962, a group of MIT students, advised by John McCarthy, developed a chess-playing program. It was based on earlier programs for the IBM 704 written by McCarthy. One of the group members, Alan Kotok (1941–2006) described the program in his MIT bachelor's thesis. The program was written in a combination of FORTRAN and machine (assembly) code and ran on the IBM 7090 computer at MIT. It used the alpha–beta procedure (as discussed earlier) to avoid generating branches of the search tree that could be eliminated without altering the final result. Kotok claimed that his program did not complete any games but “played four long game fragments in which it played chess comparable to an amateur with about 100 games experience…. Most of the machine's moves are neither brilliant nor stupid. It must be admitted that it occasionally blunders.” When McCarthy moved to Stanford, he took the program along with him and continued to work on it.