Twelve days into the strangest poker tournament of their lives, Jason Les and his companions returned to their hotel, browbeaten and exhausted. Huddled over a pile of tacos, they strategized, as they had done every night. With about 60,000 hands played -- and 60,000 to go -- they were losing badly to an unusual opponent: a computer program called Libratus, which was up nearly $800,000 in chips. That wasn't supposed to happen. In 2015, Les and a crew of poker pros had beaten a similar computer program, winning about $700,000.
Carnegie Mellon's No-Limit Texas Hold'em software made short work of four of the world's best professional poker players in Pittsburgh at the grueling "Brains vs. Artificial Intelligence" poker tournament. Poker now joins chess, Jeopardy, go, and many other games at which programs outplay people. But poker is different from all the others in one big way: players have to guess based on partial, or "imperfect" information. "Chess and Go are games of perfect information," explains Libratus co-creator Noam Brown, a Ph.D. candidate at Carnegie Mellon. "All the information in the game is available for both sides to see.
Don't simply "all in" if there's a bot at your Texas hold'em poker table, because Facebook and Carnegie Mellon University's new Pluribus AI system just beat five human pros at the same time -- including a couple of World Series of Poker Champs. AI models had already bettered human poker pros one-on-one, but Pluribus's success in a six-player game signals a huge leap in ability. Texas hold'em is one of the most popular poker variants that involves game theory, gambling, and strategy. To win the game, each play must assemble the best five cards from any combination of two "hole cards" dealt face down to each player and five community cards dealt face up. Players can choose to check, bet, call, raise, and fold.
The four of them had spent the last 20 days playing 120,000 hands of heads-up, no-limit Texas Hold'em against an artificial intelligence called Libratus created by researchers at Carnegie Mellon University. A similar scene had unfolded two years prior when Les, Kim and two other players decisively laid the smackdown on another AI called Claudico. The players hoped to put on a repeat performance, finish up the event January 30th, and ride the rush of endorphins until they got home and resumed their usual games of online poker. The fight wasn't even close. All told, Libratus won by more than 1.7 million (virtual) dollars, and -- just like that -- the second Brains vs. AI competition came to a close.