AlphaGo, the Go playing program developed by Google’s DeepMind, scored its first victory in the match against Lee Sedol.
This win comes in the heels of AlphaGo victory over Fan Hui, the reigning 3-times European Champion, but it has a deeper meaning, since Lee Sedol is one of the two top Go players in the world, together with Lee Changho. Go is viewed as one of the more difficult games to be mastered by computer, given the high branching factor and the inherent difficulty of position evaluation. It has been believed that computers would not master this game for many decades to come.
AlphaGo used deep neural networks trained by a combination of supervised learning from professional games and reinforcement learning from games it played with itself. Two different networks are used, one to evaluate board positions and another one to select moves. These networks are then used inside a special purpose search algorithm.
The image shows the final position in the game, courtesy of Google’s DeepMind.