Lee Sedol has overcome some formidable players over his professional Go career, but now he has been taken down a peg by a new type of opponent. Google's AlphaGo computer program has taken out the first in a five-match series against the South Korean, marking a major milestone in the advancement of artificial intelligence.
The AlphaGo program was actually built by artificial intelligence company DeepMind, which Google acquired in early 2014. Just as IBM's Watson became famous for beating the world's best Jeopardy players, AlphaGo is looking to demonstrate its problem-solving prowess by overcoming human opponents at the top of their game.
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But where computers have mastered other games like chess and checkers, the ancient Chinese game of Go presents a different challenge entirely. Players take turns placing black or white stones on a grid-patterned board, trying to surround and trap the opponent's pieces. But the stupendous amount of possible positions, which amount to more atoms than are in the universe, partnered with the human intuition required to play the game at a high level has made it a hugely difficult, yet irresistible challenge for AI researchers.
In designing AlphaGo with the goal of becoming the best Go player in the world, the team built an advanced search tree to comb through all the possible positions and combined it with deep neural networks, which were trained on 30 million moves from games played by human experts. They then enabled AlphaGo to conceive its own strategies by playing thousands of games among these neural networks and making adjustments through trial and error.
In its bout with Lee Sedol, AlphaGo weathered some aggressive play from the 9-dan-ranked player, but managed to keep pace and ultimately prevail. Commentator Michael Redmond said that Sedol held a promising position up until a certain point late in the game, but one mistake was all AlphaGo needed to go on and seize victory.
The four remaining matches will take place over the coming days and finish up on Tuesday March 15. There is US$1 million in prize money at stake, though if AlphaGo does win this will be donated to charity.
You can see watch a quick roundup of the historic first match below.