Until recently, AI programs could only beat very low-level players, which made DeepMind's victory over Fan Hui such a surprise. Because of the nearly infinite moves possible in the game, DeepMind doesn't try to calculate ahead like chess computers do. Rather, programmers "taught" it the strategies used by Go masters, then had it play numerous virtual games to reinforce them.
DeepMind topped three time European champ Fan Hui, who is ranked as a "2 dan" player. However, Lee Sedol is ranked in the stratospheric "9 dan" category, so he'll provide a more formidable challenge. "I have heard that Google DeepMind's AI is surprisingly strong and getting stronger, but I am confident that I can win, at least this time," said Lee. By saying "this time," Lee is nodding to the rapid progress that Google has made in the complex game -- experts had predicted it would take another ten years for computers to beat master Go players. The match will take place between March 9-15, and Google's Hassabis will reveal more details about the livestream soon.