AlphaGo responded "calmly" to the anomaly, playing aggressively to Lee who in turn took counterattacks against the algorithm, the commentator said.
Lee's slight domination by the middle of the match was reversed as AlphaGo infiltrated into the right areas of black put by the human champion. He tried to change the situations in his favor, but he finally admitted his defeat after his 186th placing.
As Lee got the black which allows his faster starter than AlphaGo, Lee had to win 7.5 areas more than AlphaGo as a handicap for victory, according to Chinese Go rules adopted in the match.
Go originated from China more than 2,500 years ago. It involves two players who take turns putting markers on a grid -shaped board to gain more areas on it. One can occupy the markers of the opponent by surrounding the pieces of the other.
To cover the human versus AI fight, hundreds of journalists gathered at the venue from around the world. The match was broadcast live through TVs in South Korea, China and Japan, with Google's YouTube showing it through an Internet live-stream.
Kim Hyun-jin, wife of Lee Sedol, and their daughter Lee Hye-lim who came to the venue to watch Lee's match, were surrounded by lots of local and foreign journalists at the corner of the hotel for interviews while the match was going on.
At the VIP room, South Korean politicians and senior government officials watched the landmark game, including floor leader of ruling Saenuri Party, head of the main opposition Minju Party, Seoul Mayor Park Won-soon and other government officials.
After the announcement of Lee's defeat, people watching the match in and around the venue voiced a sigh over the unexpected loss of the human champion.
Lee has won world Go champions 18 times in the past 11 years, recording a winning rate of about 70 percent with 47 victories in professional matches. AlphaGo has recorded a 99.8 percent winning rate with 504 victories and only one defeat.
With the victory, Google is expected to enjoy great promotional effects from the match of the century, which is also forecast to help Go, known as Weiqi in China and Baduk in South Korea, gain popularity in Western countries as well as in Asia.
The promotion effect is estimated to reach at least 100 million U.S. dollars in consideration of worldwide attention and news media reports from Western countries as well as Asian nations. Google allegedly has invested about 2 million dollars, including 1 million dollars in prize, for the landmark event.
The match drew great attention from news organizations, Go fans and even the general public around the world. With the victory, AlphaGo developer DeepMind could gain reputation as one of the world's leading AI companies.
AlphaGo boasts of its deep learning, a capability of learning to discover new strategies for itself by playing thousands of games between its neural networks and adjusting connections by use of a trial-and-error process known as reinforcement learning.
The world AI market is forecast to grow to nearly 2 trillion dollars by 2025, expanding its application to various fields such as healthcare, disease analysis and even legal advices.
The match between Lee and AlphaGo is also projected to help the Chinese board game gain popularity in Western countries as well as in Asia.
