Computer program rivals top poker players in complex card game

The inaugural battle between human and machine in heads-up no-limit Texas Hold’em poker has ended in a statistical draw.

After playing 80,000 hands between April 24 and May 8, a computer program called Claudico amassed slightly fewer chips than its opponents, four top-10 poker professionals; however, the deficit was not large enough to determine conclusively that the computer was the weaker player. While researchers have created programs that are practically unbeatable at limit Hold’em, no-limit Hold’em is much more complicated because of all of the possible betting combinations.

Claudico’s skill comes from applying game theory to the rules of poker rather than studying human players’ moves, says Tuomas Sandholm, who leads the Claudico team at Carnegie Mellon University in Pittsburgh. As a result, the program employs an unpredictable strategy that often bucks conventional wisdom. It loves to use the frequently derided tactic of limping — calling the big blind bet instead of folding or raising. Claudico is Latin for “I limp.”