Poker-playing AIs typically perform well against human opponents when the play is limited to just two players. Now Carnegie Mellon University and Facebook AI research scientists have raised the bar even further with an AI dubbed Pluribus, which took on 15 professional human players in six-player no-limit Texas Hold ’em and won. The researchers describe how they achieved this feat in a new paper in Science.
Playing more than 5,000 hands each time, five copies of the AI took on two top professional players: Chris “Jesus” Ferguson, six-time winner of World Series of Poker events, and Darren Elias, who currently holds the record for most World Poker Tour titles. Pluribus defeated them both. It did the same in a second experiment, in which Pluribus played five pros at a time, from a pool of 13 human players, for 10,000 hands.
Co-author Tuomas Sandholm of Carnegie Mellon University has been grappling with the unique challenges poker poses for AI for the last 16 years. No-Limit Texas Hold ’em is a so-called “imperfect information” game, since there are hidden cards (held by one’s opponents in the hand) and no restrictions on the size of the bet one can make. By contrast, with chess and Go, the status of the playing board and all the pieces are known by all the players. Poker players can (and do) bluff on occasion, so it’s also a game of misleading information.