Dahl worked on this problem for many years. The obstacle was that he had almost no idea how his poker bot actually worked. The structure of its neural net was no easier to interpret than the nervous system of an invertebrate, and trying to tease out game-playing strategies by examining the individual weights of the grid was like trying to unravel consciousness
by looking at brain cells through a microscope. This was the criticism of neural nets and the thing that so biased the academic community against them. Once a neural net hit a training plateauâand they almost always didâthere was rarely an obvious way to make it better. Classical programming was orderly and logical, but tinkering with neural nets required a different cast of mind. Dahl compared it to running a biology experiment: outcomes were unpredictable, and altering seemingly minor variables could have all manner of unanticipated results. Dahl tried everything he could think of to improve his no-limit poker bot. He fiddled with its evaluation function, he futzed with his computerâs memory, he replaced the activation trigger for the neurons, he even synthesized a simpler data universe for the bot to exploreâbut he never got it to play at an expert level.