Computer Chess Champ Sees Moves Out Of The Blue
Three months ago, the computer scientists at IBM discovered a bug in their now-famous chess machine, Deep Blue. For some reason, as the computer searched way out along the lines of possibilities in examining certain moves, it began seeing a queen where there wasn’t one, a kind of computer hallucination.
“All over the place, Deep Blue was thinking there was an extra queen on the road,” said Joe Hoane, a scientist on the Deep Blue team.
The alarming discovery came during the home stretch in the preparation of the computer for its rematch with Garry Kasparov, the world chess champion, who had roundly defeated it in February 1996.
The culprit, it turned out, was a newly designed chip linking Deep Blue’s powerful multiprocessors with its chess software. It took two weeks to adjust the software and fix the bug.
The image of a magically appearing queen nicely represents the accomplishments of Deep Blue, which a week ago made history by whipping Kasparov in a six-game match. Deep Blue sees things, at least on occasion, that no other machine, or human, can see. Unlike the queen, most of them are really there.
The match ended in an atmosphere of hostility and suspicion, and Kasparov expressed his frustration again and again in terms that had to do with the machine’s magic. During the match, he attributed one move to “the hand of God.”
“It’s very difficult to analyze the results of the match,” Kasparov said. “I know what I did wrong. But I don’t know what the computer did wrong or right. It’s a mystery.”
What particularly irks Kasparov is his sense that it was not Deep Blue’s awesome calculating ability - it can examine 200 million moves per second - that defeated him. It was its ability to evaluate those positions. It seemed, he said, to understand complexities of chess that no other computer has come close to duplicating. The explanation lies, apparently, in the contributions of Joel Benjamin, a grandmaster who joined the Deep Blue team in August.
He played position after position against Deep Blue, filling up notebooks with observations.
He was trying to determine the occasions during which the computer’s sense of a chess position was incomplete or unsophisticated.
“For example,” Benjamin said, “I noticed that whenever Deep Blue had a pawn exchange that could open a file for a rook, it would always make the exchange earlier than was strategically correct. Deep Blue had to understand that the rook was already well-placed and that it didn’t have to make the exchange right away. It should award evaluation points for the rook being there even before the file is opened.”
This gets at Kasparov’s frustration. The so-called mystery is the computer’s ability, at least at some points, to play what is called positional chess, a concept that is difficult to define.
Positional chess involves a situation in which there are no clear objectives on the board, no obvious squares to be commandeered. It is a kind of jockeying, with the two sides maneuvering for position, from which to begin long-term plans. It is the kind of chess that grandmasters generally say they play better than machines, because the power of individual moves is subtle, deeply resonant, rather than calculable.