South Korean Go master Lee Se-dol said Wednesday he was impressed by the machine-like behavior of a Google programmer who was placing stones for the artificial intelligence program AlphaGo during the historic man-versus-computer tournament.

Lee left for a vacation on Jeju Island with his wife and daughter earlier in the day after playing the five-round Go event against AlphaGo, the AI developed by Google's London-based firm DeepMind. The tournament, named the Google DeepMind Challenge Match, ended on Tuesday with a final score of 4-1 in AlphaGo's favor.

Lee, a professional ninth-dan player with 18 international titles, collected his only victory against the human-like algorithm Sunday.

For the landmark showdown played at a Seoul hotel, Lee said Aja Huang, a Google DeepMind programmer and amateur 6-dan Go player who was placing stones on the board after watching AlphaGo's moves on the monitor, was one of the top contributors to making the matches interesting.

"I think he was one of the most hard-worked people in the tournament," Lee told Yonhap News Agency at Gimpo International Airport in Seoul before departing to Jeju Island. "Throughout the tournament, he had no change of facial expression and never went to the restroom."

Lee, however, said that Huang's emotionless behavior didn't affect his game. The 33-year-old said the Google researcher is a "good guy," trying not to distract him from the game.

"I think he was just trying to keep his manners," Lee said. "He not only did not go to the restroom, but also didn't drink water."

Lee, who brought a cup of coffee and went to the restroom on several occasions during the tournament, said he at one point felt that Huang could be AlphaGo itself.

"I did have a feeling that he could be the main body of AlphaGo," Lee said with a laugh. "This tournament was a matchup between the AlphaGo-Aja Huang team and Lee Se-dol, a two versus one game."

According to Lee's wife Kim Hyun-jin, her husband even mentioned the Google researcher's name in his sleep.

"I tried to wake him (Lee) up for breakfast, but he said he will eat with Aja Huang," she said. 

Lee, who said he can't remember what he dreamed last night, said he will stay in Jeju Island for about a week with his family. Lee's wife and daughter have been living in Canada, but came to South Korea on March 6 to support their breadwinner. Last Saturday was Lee and his wife's 10th wedding anniversary, but the Go master had to hold off on celebrating because of the match with AlphaGo. (Yonhap)