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Comment by jdoliner | Hacker News Reader

Hi guys, author here. I'll be monitoring this thread for the rest of the evening. Happy to answer any questions.

Hi! Did you consider modeling the fact that a blunder in the first ten move-pairs seems far less likely in expert play, given that they're usually playing from book and there are fewer pieces in motion to consider?

(I'm wondering if blunders after move 15 are in fact far more common than your model suggests, and they're just being extremely diluted in your stats by correct opening play almost every game.)

You're totally right about this. In general the efficacy of engines is different for different parts of the game. In the beginning players (and engines) are mostly playing from books so there's a lot fewer mistakes and what the engine thinks of as a mistake is just someone going outside its pre defined book. Mid game the analysis is very effective. In end game the engine can actually completely solve the game, so it really just judges moves as winning or losing.

Spoiler: We're planning to address a lot of this in an upcoming followup I'm working on right now. We're going to take this in to account in our analysis as well as giving people the raw dataset with info about when the blunders occurred so that can learn from it themselves.

« Assuming Anand and Carlsen’s blunders were independent events, what we saw was a 1 in 10,000 occurrence. »

Are they independent events though? In a game between mediocre players, if there is only one move to take advantage of a blunder, the computer analysis will repeatedly cry "blunder!" each turn until either that move is played or the initial blunderer defuses the opportunity. As for grandmaster play, I have no clue.

My hypothesis would be that GMs are much less likely to blunder when there's a winning move on the board. They're generally very good at finding such moves.

What time controls were you looking at? I'm half-jokingly wondering if the big dip of correct moves in the upper 2800 range is Nakamura's crazy opening style :) (He's rated upper 2800's in blitz and rapid)

My guess: the only one that has been rated in that bucket in the last year was Caruana, post-Saint Louis. At that point, he suffered (and is still going through) a big decline with several bad blunders.

This was the leading hypothesis on r/chess. I'm pretty sure it's right Naka didn't hit this rating in 2014 as far as I know.

The only other candidate would be Carlsen when he dipped to the high 2850s.

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