Deep Blue’s 44th move

This is a quote from Nate Silver’s book “The Signal and the Noise: Why So Many Predictions Fail — but Some Don’t”. He talks about a strange move (move 44) made by the chess robot “Deep Blue” against Chess Champion Garry Kasparov.

Deep Blue did something very strange, at least to Kasparov’s eyes. On its forty-fourth turn, Deep Blue moved one of its rooks into white’s first row rather into a more conventional position that would have placed Kasparov’s king into check. The computer’s move seemed completely pointless. At a moment when it was under assault from every direction, it had essentially passed its turn, allowing Kasparov to advance one of his pawns into black’s second row, where it threatened to be promoted to a queen. Even more strangely, Deep Blue resigned the game just one turn later.

What had the computer been thinking? Kasparov wondered. He was used to seeing Deep Blue commit strategic blunders–for example, accepting the bishop-rook exchange–in complex positions where it simply couldn’t think deeply enough to recognize the implications. But this had been something different: a tactical error in a relatively simple position–exactly the sort of mistake that computers don’t make.

“How can a computer commit suicide like that?” Kasparov asked Fredric Friedel, a computer chess journalist who doubled as his friend and computer expert, when they studied the match back at the Plaza Hotel that night. There were some plausible explanations, none of which especially pleased Kasparov. Perhaps Deep Blue had indeed committed “suicide,” figuring that since it was bound to lose anyway, it would rather not reveal any more to Kasparov about how it played. Or perhaps, Kasparov wondered, it was part of some kind of elaborate hustle? Maybe the programmers were sandbagging, hoping to make the hubristic Kasparov overconfident by throwing the first game.

Kasparov did what came most naturally to him when he got anxious and began to pore through the data. With the assistance of Friedel and the computer program Fritz, he found that the conventional play–black moving its rook into the sixth column and checking white’s king–wasn’t such a good move for Deep Blue after all: it would ultimately lead to a checkmate for Kasparov, although it would still take more than twenty moves for him to complete it.

… As Friedel recalled:
‘Deep Blue had actually worked it all out, down to the very end and simply chosen the least obnoxious losing line. “It probably saw mates in 20 and more,” said Garry, thankful that he had been on the right side of these awesome calculations.’

To see twenty moves ahead in a game as complex as chess was once thought to be impossible for both human beings and computers. Kasparov’s proudest moment, he once claimed, had come in a match in the Netherlands in 1999, when he had visualized a winning position some fifteen moves in advance. Deep Blue was thought to be limited to a range of six to eight moves ahead in most cases. Kasparov and Friedel were not exactly sure what was going on, but what had seemed to casual observers like a random and inexplicable blunder instead seemed to them to reveal great wisdom.

Kasparov would never defeat Deep Blue again.”

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