The Poker Playing AI

As we know that the game of Poker involves dealing with imperfect information, which makes the game very complex, and more like many real-world situations. At the Rivers Casino in Pittsburgh this week, a computer program called Libratus (A latin word meaning balanced), an AI system that may finally prove that computers can do this better than any human card player. Libratus was created by Tuomas Sandholm, a professor in the computer science department at CMU, and his graduate student Noam Brown.

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The AI Poker play against the world’s best poker players. Kim is a high-stakes poker player who specializes in no-limit Texas Hold ‘Em. Jason Les and Daniel McAulay, two of the other top poker players challenging the machine, describe its play in much the same way. It does a little bit of everything,” Kim says. It doesn’t always play the same type of hand in the same way. It may bluff with a bad hand or not. It may bet high with a good hand—or not. That means Kim has trouble finding holes in its game. And if he does find a hole, it disappears the next day.

“The bot gets better and better every day. It’s like a tougher version of us,” said Jimmy Chou, one of the four pros battling Libratus. “The first couple of days, we had high hopes. But every time we find a weakness, it learns from us and the weakness disappears the next day.”

Libratus is playing thousands of games of heads-up, or two-player, no-limit Texas hold’em against several expert professional poker players. Now a little more than halfway through the 20-day contest, Libratus is up by almost $800,000 against its human opponents. So a victory, while far from guaranteed, may well be in the cards.

Regardless of the pure ability of the humans and the AI, it seems clear that the pros will be less effective as the tournament goes on. Ten hours of poker a day for 20 days straight against an emotionless computer was exhausting and demoralizing, even for pros like Doug Polk. And while the humans sleep at night, Libratus takes the supercomputer powering its in-game decision making and applies it to refining its overall strategy.

A win for Libratus would be a huge achievement in artificial intelligence. Poker requires reasoning and intelligence that has proven difficult for machines to imitate. It is fundamentally different from checkers, chess, or Go because an opponent’s hand remains hidden from view during play. In games of “imperfect information,” it is enormously complicated to figure out the ideal strategy given every possible approach your opponent may be taking. And no-limit Texas hold’em is especially challenging because an opponent could essentially bet any amount.

“Poker has been one of the hardest games for AI to crack,” says Andrew Ng, chief scientist at Baidu. “There is no single optimal move, but instead an AI player has to randomize its actions so as to make opponents uncertain when it is bluffing.”

(Sources: MitTechReview, The Verge, Wired)

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