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AI as Sport
Kasparov versus Deep Blue. Computer Chess Comes of Age. MONTY NEW-
BORN. Springer-Verlag, New York, 1996. xiv, 322 pp., illus. $29.95 or DM
49.90. ISBN 0-387-94820-1.
This review appeared in Science on 1997 June 6. The version here may be
improved from time to time.
Last month’s victory of the IBM computer Deep Blue over world chess
champion Garry Kasparov culminates a 22-year engineering eﬀort. It was
also a major sporting event.
Monty Newborn, who has been an active organizer of computer chess
tournaments and helped arrange the Kasparov-Deep Blue matches, here re-
counts the 50 years of computer chess that led to the preceding, 1996, match,
won by Kasparov.
Ideas about chess algorithms as well as advances in computer hardware
were involved. However, it is a measure of our limited understanding of the
principles of artiﬁcial intelligence (AI) that this level of play requires many
millions of times as much computing as a human chess player does. Moreover,
the ﬁxation of most computer chess work on success in tournament play has
come at scientiﬁc cost.
In 1965 the Russian mathematician Alexander Kronrod said, ”Chess is the
Drosophila of artiﬁcial intelligence.” However, computer chess has developed
much as genetics might have if the geneticists had concentrated their eﬀorts
starting in 1910 on breeding racing Drosophila. We would have some science,
but mainly we would have very fast fruit ﬂies.
Three features of human chess play are required by computer programs
when they face harder problems than chess. Two of them were used by
early chess programs but were abandoned in substituting computer power
1) Human chess players cannot examine all moves at every position they
think about and therefore must forward prune the move tree and select the
more promising moves for exploration; early chess programs also pruned.
About 1969 forward pruning was eliminated, and computer power was relied
upon to examine all moves. It made the programs work better, because early
programs sometimes pruned good moves. Eliminating pruning was possible,
because there are only about 40 moves in a position. In the game of Go,
there are up to 361 moves in a position, so even computers must forward
2) An early Soviet program could consider certain moves as analogous to
moves that had been found to be bad in a parallel position. It would prune
them unless something was observed that would rehabilitate them. This also
was abandoned. Present programs spend most of their time rejecting the
same moves millions of times apiece.
3) Human chess players often partition a position into subpositions, for
example the king’s side and queen’s side. We analyze the subpositions some-
what separately and then consider their interaction. Present chess programs
only consider the position as a whole, and computer power makes up for
the ineﬃciency. Computer Go programs are weak, because partitioning is
absolutely necessary for Go. We still don’t know how to make computers
partition eﬀectively. Imagine playing wide chess on an 8-by-32 board. Hu-
mans would play almost as well as on the normal board, because humans
use partitioning on all problems, but programs based on present principles
would be unable to search deeply.
Much would have been learned had these important intellectual mecha-
nisms not been rejected for tournament chess programs.
Newborn developed chess programs named Ostrich between the 1960s
and 1982, especially versions running on parallel processors. His book is an
accurate history of tournament-oriented computer chess and explains many
of the ideas present in today’s programs. Like other chess books, it includes
the scores of many of the important games. However, his conventional chess
commentary takes almost no advantage of the possibilities computers oﬀer
to determine which lines of play were actually examined and how much time
was spent on them.
Now that computers have reached world-champion level, it is time for
chess to become a Drosophila again. Champion-level play is possible with
enormously less computation than Deep Blue and its recent competitors use.
Tournaments should admit programs only with severe limits on computation.
This would concentrate attention on scientiﬁc advances. Perhaps a personal
computer manufacturer would sponsor a tournament with one second allowed
per move on a machine of a single design. Tournaments in which players use
1Newborn mentions the abandonment of forward pruning as an important advance
made by Slate and Atkin in 1969, and David Slate mentioned it in his talk at the AAAI
awards ceremony in 1997 July. However, I was informed that Deep Blue does some forward
pruning deep in the tree.
computers to check out lines of play would be man-machine collaboration
rather than just competition.
Besides AI work aimed at tournament play, particular aspects of the
game have illuminated the intellectual mechanisms involved. Barbara Liskov
[?] demonstrated that what chess books teach about how to win certain
endgames is not a program but more like a predicate comparing two positions
to see if one is an improvement on the other. Such qualitative comparisons
are an important feature of human intelligence and are needed for AI. Donald
Michie, Ivan Bratko, Alen Shapiro, David Wilkins, and others have also used
chess as a Drosophila to study intelligence. Newborn ignores this work,
because it is not oriented to tournament play.
Research support agencies have trouble with the idea of chess as a Drosophila.When I explained to a DARPA program manager in the 70s how a student’s
program that discovered mating combinations contributed to recognition of
complex patterns in general, he replied, ”Well all right, but when he publishes
his dissertation, would he kindly not acknowledge our support.” I suspect
that in big companies today, it may be easier to justify work on computer
chess as a means of getting publicity than as a research tool.
An extended commentary on making computer chess more scientiﬁc is
available at http://www-formal.stanford.edu/jmc/chess.html2.
Department of Computer Science,
Stanford, CA 94305-9120, USA
/@steam.stanford.edu:/u/ftp/jmc/newborn.tex: begun Fri Jun 13 17:24:28 1997, latexed August 25, 1997 at 5:57 p.m.