Korean Go guru Lee-Se-dol beat supercomputer AlphaGo in the fourth round of the best-of-five match series on Sunday in one of the most closely watched competitions between the human mind and artificial intelligence after three consecutive defeats. Although the contest already has been determined, Sunday’s match was not only a face-saving victory for the 33-year-old world champion dubbed as the best living player of the ancient 19-by-19 grid board game but also for Korea, the traditional Go powerhouse whose reputation has recently been threatened by Chinese players. Lee himself called the experience “priceless” to the crowd of roaring reporters and fans after the computer flashed “AlphaGo resigns” with one minute left in the match that lasted for nearly five hours as he was largely expected to be overwhelmed by the rapidly self-evolving AI in a landslide.

Demis Hassabis, the head of AlphaGo developer Google DeepMind, lauded Lee’s “fantastic” play who rewarded the developer’s mission for the match in Seoul - to find out the weaknesses of its AI through mastering the game of Go that has been considered as the “Mount Everest” for AI scientists.

“Actually we are very happy because this is why we came here, to test AlphaGo and its limit and find out what its weaknesses were.”

Lee, who had been under enormous public pressure, said “Compared to human beings, its moves are different and at times superior. But I do think there are weaknesses for AlphaGo” including its difficulty of responding to certain unexpected plays and weakness against the movements of black stones in the game where two players take turn to place black or white pieces called stones to encircle as much empty space as possible as territory.

AlphaGo stunned the world through its capacity to learn and mimic human mind by digging into the “deep neural networks” running on a vast network spanning over 170 graphic processing units and 1,200 standard processors to make it move more human-like fashion.

The last of the five-series game takes place on Tuesday in the Four Seasons Hotel in Seoul which would deliver Lee $20,000 for a single win on top of $150,000 for participating in the series.

By Lee Gyung-jin, Cho Hee-young

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