Lee Sedol says AlphaGo has weak points after 1st win in Go match

South Korean Go grandmaster Lee Sedol said on Sunday that Google's computer program AlphaGo has weak points after his first victory over the Go-playing artificial intelligence (AI) in the fourth of the best-of-five series at the ancient Chinese board game.

"There are two weak points AlphaGo revealed," Lee told a press conference after the game, which is seen as a representative match between humans and AI.

Lee said AlphaGo seemed to feel difficult to play when it grabs black stones. He also noted that AlphaGo made some moves of a "bug" type when he made unexpected moves, saying AlphaGo's capability of dealing with unexpected moves.

Playing black, AlphaGo displayed questionable moves, which commentators said must be mistakes and algorithm errors, when Lee attacked at the center of the board set up by the supercomputer around the middle of the game.

About three hours into the game, Lee began to dominate the match and maintained the winning mood until the end.

Go originated from China thousands of years ago. It involves two players who take turns putting black and white stones on a grid of 19 lines by 19 lines. One can win an opponent when securing more areas by surrounding vacant territory with stones.

Lee expressed his hope for another victory in the final match with black stones, with which AlphaGo looked difficult to play, saying that it would be more worthy.

Regarding asymmetric information between Lee and AlphaGo, Lee told reporters that it was not a great issue, saying he lost the previous three games due to his lack of capability though he admitted that he would have played more easily if he had some information on AlphaGo before the match.

Lee expressed gratitude for cheers and congratulations from the public, saying it was a priceless victory which he will not replace with anything.