I doubt pros are going to play any single moves that are as bad as passing (exclude blunders like Nakano's self atari!), though after 50 moves of a bad opening against AlphaGo I could well believe they are about a stone down. It's an interesting question what "win%" would it give for passing, but probably we can't know (unless I can persuade Aja or Lucas to ask!), though maybe we could ask another strong bot? I do wonder though how much confidence you can give to its answer though, as in its training it will have seem very few positions with one player passing! But pros are sensitive to tiny losses, for example in this very common opening when I was at BIBA On Sojin 7p said he considered the pincer of 6 a slight mistake (379 games in waltheri) and better to back off at
a (1174 games) and black just taking the corner is fine for him (he assumed the normal solid connect joseki which AG disapproves of). AG agrees pincer is worse, by 2%. He thought pincer was ok if black's bottom right was at
b because then if white gets sente after black takes the corner he has a good approach there, and you are trying to prevent black making nice mini-Chinese style formations whereas the 4-4 isn't threatening to make anything particularly good. With 3-4 AG thinks pincer is the same 2% worse, though now back off is not best move but wants to approach white immediately (as an aside this does seem to be a valuable general lesson from this tool, it often prefers to approach an open 3-4 over answering an approach to a 4-4, as was perhaps the thinking in older opening theory).
- Click Here To Show Diagram Code
[go]$$B
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Browsing the WeiqiTV videos I do find the biggest total win% drop I've seen; this position black is at 23%. I've always thought that joseki is pretty ugly for black, but do recall being taught (maybe on China trip from Peter Liu 2p) that it's definitely bad if black's lower stone is at k4 (because h3 gap), but with L4 instead it's better (though maybe still bad overall). (AG doesn't give this line with k4). AG does also say o4 extend is better than o5 atari, which I seem to recall Go Seigen suggesting in his 21st century opening book.
- Click Here To Show Diagram Code
[go]$$Bc
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$$ | . . . . . . . . . . . . . . O X . . . |
$$ | . . O . . . . . . . . . . X X O O . . |
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$$ | . . . O . . . . X , . . X . X X X O . |
$$ | . . . . . X . . . . . . . X O X O . . |
$$ | . . . . . . . . . . . . . . O O . O . |
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$$ +---------------------------------------+[/go]
P.S. I think a change in the underlying "win%" metric of half a percent is significant if a pro wants to play the best opening, but also the numbers we get in the tool have some noise of about half a percent.