Yeah according to Redmond, it seemed that AlphaGo made a few "mistakes" whereas Sedol made none. And yet AlphaGo came out substantially ahead. So I'm not sure what that means. Perhaps we need to see more in-depth analysis of the moves, but it seems that AlphaGo just out-calculated Sedol.

I wonder if their move selection algorithm takes into account the "surprise" factor: given two moves that are almost equal in strength when analyzed to a depth of N, chose the one that looks worst at N-1. That is, if all else is equal, assume that you can search deeper than your human opponent, and lay traps accordingly.

Besides trap-laying, there's also a second useful "surprise" factor: your opponent is likely to have spent time on your clock to read out follow-ups to your most likely move. By throwing in an unlikely (but still good!) move you're forcing them to expend time on their clock to re-think their follow-ups.

That's interesting. And a sign of truly understanding what a human would think.

Btw. There's a concept in Go called "overplaying". That means selecting a move that isn't objectively the best you could come up with, but that is most confusing, considering the level of the opponent. It's generally thought of as a bad practice, and if you misestimated the level of your opponent, she can punish you by exploiting the fact you didn't play your best move.

If they do that, they didn't tell anyone at Google.

I don't know about surprise, the the AKA stream was pretty shocked when AlphaGo was playing aggressively from the 5th line/column from the right early in the game. Apparently going in on the 3rd is already very risky and the 4th is almost never done.

According to DAVID ORMEROD in his commentary at https://gogameguru.com/alphago-defeats-lee-sedol-game-1/, black (Lee Sedol) made plenty of mistakes from the start to the end, and they were seriously questioning his form. White (AlphaGo) made only a few mistakes in the middle, which allowed Black to catch up a bit, but he had no chance, esp. in the endgame.

maybe the mistakes were unrecognized brilliant moves (tesujis).

I would love to see an expert analysis of the game, but there were definitely a few moves where AlphaGo was "pushing from behind" that were probably not what an expert human would play.

I think that's the point of reacweb: alphago might already be beyond expert human level understanding.

TD-Gammon was at that point for a while in the early 90s, but the experts caught up, and this changed the generally accepted Backgammon strategies.

Lee had quite a bit of advantages in the middle then he made one bad mistake and that was it. Deepmind made some smaller mistakes too but not as bad.

I am really excited about the Deepmind though. Looking forward to tomorrow's game!

What was the mistake that Lee made?

EDIT: good postmortem here https://gogameguru.com/alphago-defeats-lee-sedol-game-1/

Yeah. It was the bottom right corner that I talked about. But some speculation says it was part of AlphaGo's plan so I am extremely looking forward to today's game now.

According to Myungwan Kim, 9p, commenting on the game in the AGA channel [1], Lee Sedol made a mistake right at the beginning and spent the rest of the game hoping to claw it back; he said he would resign about 15 min before he did.

EDIT: but this postmortem [2] of the game is far more nuanced and doesn't reach the same conclusion.

[1] https://www.youtube.com/watch?v=6ZugVil2v4w [2] https://gogameguru.com/alphago-defeats-lee-sedol-game-1/