Position D is problem 17 from the book. Black needs to defend the bottom left group--but exactly which move is best?

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[go]$$c Position D. Black to play.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . O . . . O . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . W . . . . . . . . . . . . . . . . |
$$ | . a b . . . . . . . . . . . . . . . . |
$$ | . c d X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X , O . . . . , . . . . . , X . . |
$$ | . . . X O . . O . . e . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Now I'm sure I've seen the bottom left position as a problem in a book, although I can't remember exactly where, and 'd' was promoted as an example of honte, leaving no weaknesses in the corner and getting ready to pincer . Indeed 'd' is the book move, but only AQ had it as first choice. All the other bots picked 'a', mostly as the only move examined, except that GX-47 had 'c' as second choice and AQ had 'b' as second choice. Regardless of which move is chosen, white wants to play 'e' pretty soon.

I also searched GoGoD (Spring 1998, with help from Kombilo) for this shape and found 23 hits. Black played 'b' and 'd' 11 times each and 'c' once, with no occurences of the bots' favourite move.

KataGo evaluations and followup moves:

Position E is problem 19 from the book. The key issue is how to deal with white's moyo at the top left -- or is it?

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[go]$$c Position E. Black to play.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . X . . . . |
$$ | . . . , . . O . . X . . . . . , X . . |
$$ | . . c b . . . . . . . . . . . . e . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . d . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . a . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . X . . . . . , . . . |
$$ | . . f . . X . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The book move is 'a'. The bots generally thought the top right was more interesting: black should play 'd', or if black plays elsewhere then white will play 'e' soon.

• 'a' was the book move.
• 'd' was first choice for LZ-242, GX47, KataGo and Ray.
• ELF chose 'b'.
• AQ chose 'c'.
• GX47 threw out 'f' as a close second choice.

KataGo evaluations and followup moves: