Texas hold'em poker has become an increasingly popular game over the last 10 years, and represents a significant challenge to tackle from a computational perspective. The minimax algorithms which successfully spawned nearly unbeatable chess players break down when applied to poker. In 2007 and 2008 two programs were created (building on the prior work of many other researchers) that attempt to tackle the game of limit heads-up texas hold'em.
The strategy for Fell Omen 2 and INOT were generated in a similar manner. A Co-evolutionary process called fictitious play was used to create a near optimal solution to the game. Fictitious play is an iterative algorithm that works roughly as follows.
The result is that the strategies of INOT and Fell Omen 2 do not pop out of thin air, but are rather grown by a process of self examination. This may be similar to the way a human might learn a game. Like these bots a human starts off playing poorly, not really getting how good a given poker hand is, and how often to bluff. he/she then examines the way their strategy is exploited, and makes adjustments.
After the learning process is completed, we are left with a robust strategy set that gives raise call and fold probabilities for any given situation. Thus, after the initial learning of the game, no further adjustments are made no matter what type of opponent the program is facing.
Using the term artificial intelligence with these bots is really a misnomer. There is no 'thinking' going on. When playing, they are simply looking up in a table what the appropriate action for a given situation is. So how can something that has no capability for reason know when to bluff?
The answer is that there is nothing inherently human about bluffing. Bluffing isn't reading into the soul of your opponent and knowing when you can run them over. Rather, it is a necessary strategic move, just like raising a good hand. Bluffing is advantageous for two reasons.
Though not perfect, INOT and Fell Omen play at a very advanced level. They were very successful in eradicating weaknesses, and what is left are robust bots whose play exhibits all of the advanced strategic tools necessary to beat expert humans.
Follow the links below for information about my poker research:
I'm very happy to see all of the interest that has been expressed over these bots (welcome stumblers). I would like to clarify two points which have caused some confusion.
An article about my work, and the work of the CPRG at the University of Alberta appeared in the Union tribune today
One nit picky point: Fell Omen 2 does not "have no weaknesses," as it was clearly beaten by Hyperborean. What I said was that it attempts to make its self unbeatable by leaving no room for exploitation.