Inside the 20-Year Quest to Build Computers That Play Poker

Four of the best professional poker players in the world spent most of January holed up at the Rivers Casino in Pittsburgh, losing. They’d show up before 11 am, wearing sweatpants and stylish sneakers, and sit down in front of computer screens. Each of them was supposed to play 1,500 hands of heads-up no limit Texas Hold ‘Em online before they could go back to the hotel for the night. This often meant working past 10 p.m. Over the course of the day, Starbucks cups and water bottles piled up next to the players's keyboards. Chipotle bags lay at their feet.

Every time one of the players made a move, the action was transmitted to a computer server sitting five miles away at Carnegie Mellon University. From there, a signal would travel another 12 miles to their opponent, a piece of software called Libratus running at the Pittsburgh Supercomputing Center in Monroeville, a nearby suburb. Libratus played eight hands at once — two against each opponent. It moved at a deliberate pace, slow enough to drive Jason Les, one of its human opponents, a bit mad. “It makes the days longer,” said Les, an earnest, athletic-looking man who seemed eager to take a few minutes off one afternoon last week. “Waiting should not affect me whatsoever, but sometimes you’re just like, 'OK, is this going to be over yet?'”