It built most of its decision model by playing itself over "trillions of hands", according to Prof. Sandholm. You could almost think of the nightly reviews as

It built most of its decision model by playing itself over "trillions of hands", according to Prof. Sandholm. You could almost think of the nightly reviews as a similar process to a human sleeping: we benefit from memory consolidation, pruning, time to reflect, etc. I don't see giving the computer 12 hours a night to do something close to reflection and self-analysis as "cheating," or even very different from what its opponents did over Mexican food each night.