AlphaGo Beats Lee Sedol 4-1.

Back in January AlphaGo’s 5-0 defeat of Fan Hui, the reigning European champion, was a shot out of left field. Go players and AI developers alike believed that we were still some 10 years away from that feat ever occurring and the resounding defeat of a champion was rather unexpected. However many still expected the current long time champion, Lee Sedol, to come out on top given his much higher ranking. The battle was set to be decided in the same game format, 5 games with 2 hours of time for each side. Over the last week AlphaGo and Lee Sedol have been facing off in match after match and AlphaGo has emerged victorious, winning 4 out of the 5 games.

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Just like when Kasparov lost to Deep Blue AlphaGo’s victory has sent ripples through both the computing and Go communities. For technologists like me it’s a signal that we’ve made another leap forward in our quest for strong AI as we’ve developed better methods for training neural networks. The Go community is less enthusiastic about it however, coming to terms with the fact that not even their game of choice is beyond AI’s capabilities. What is interesting to see however is the conversation around AlphaGo’s style of play and the near universal idea that it has some fundamental weaknesses that top Go players will look to exploit.

Indeed Lee Sedol’s one win against AlphaGo shows that it’s no where near being the perfect player and its play style needs refinement. It seems that AlphaGo tends to calculate the most advantageous moves for both itself and for its opponent, using this as the basis for judging its future moves. However unexpected moves, ones that were pruned out of its search tree due to them being sub-optimal for its opponent, seem to throw it for a loop. This is similar to how Kasparov initially beat Deep Blue, playing moves that sent it down a non-optimal search path before making his own, far more optimal, moves. Whether or not this can be developed into a viable strategy is something I’ll leave up to the reader, but suffice to say I don’t think it’d remain a weakness for too long.

For some though Lee Sedol’s loss is merely a symbolic one as the real current champion is Ke Jie, who has a 8-2 record against AlphaGo’s last opponent. Whilst I can’t really comment on how much better of a player he is (I don’t follow Go at all) AlphaGo’s almost 5-0’d Lee Sedol and I’m sure it’d give Ke Jie a solid run for his money. I’m sure AlphaGo will continue to make appearances around the world and I’m eager to see if it can still come out on top.

One interesting thing to note is that AlphaGo did receive a little boost in computing power when facing off against Lee Sedol, getting another 700 CPUs and 30 GPUs to handle the additional calculations. However that extra hardware might not have been strictly required as the AlphaGo team has said that a single laptop version can beat their distributed one about 30% of the time. Regardless it seems the AlphaGo team thought Lee Sedol was going to be a much tougher challenge than Fan Hui and gave their AI a little boost just to be sure.

The AlphaGo team won’t be resting on their laurels after this however as they’ve got their sites set on bigger challenges, like StarCraft. I’m very much looking forward to seeing them attempt the not-so-traditional games as I think they’re a far more interesting challenge with many more potential applications.

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