Four More Games

by Anders Kierulf


AlphaGo’s victory over Lee Sedol last night was stunning. I’m still gathering my thoughts and trying to figure out what happened.

The game analysis at Go Game Guru has been very helpful. But I have to wonder whether I can trust the commentary — maybe AlphaGo knew what it was doing?

Move 80 was described by Younggil An 8p as ‘slack’. I wonder whether AlphaGo at that point already calculated that it was winning, and that eliminating the aji (latent possibilities) in that area would be the best way to reduce the risk of losing. I would love to know more about AlphaGo’s evaluation of that move.

AlphaGo demonstrated that it’s good at fighting, and would not back down from a fight. It also showed excellent positional judgement and timing, managing to invade on the right side with 102, get just enough out of that fight, and end with sente to play the huge move of 116 to take the upper left corner. And it’s not letting up in the endgame once it sees a path to victory. We have not seen any ko fights yet, but there’s no reason to believe AlphaGo couldn’t handle those well.

For the remaining games, I think Lee Sedol must establish a lead by mid game at the latest to have a chance of winning. As the game gets closer to the end, there are fewer moves to consider, and there are fewer moves for the Monte Carlo playouts to reach the end of the game, so AlphaGo will just get stronger.

Move 7 was a new move. At least, it’s not in the GoGoD database of 85,000 professional game records. With SmartGo’s side-matching, only two games (both played in 2013) match that right-side position. He probably tried to make sure AlphaGo couldn’t just rely on known patterns, but that gambit didn’t pay off. I don’t think Lee Sedol will try a similar move tonight.

There are four more games; I would not count Lee Sedol out yet. He now knows what AlphaGo can do, and won’t underestimate it again. We have some very exciting games to look forward to.