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[go]$$Bcm15 Textbook play
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . . . . . . . . . . . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . . . 3 . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O , . . . . . , . . . . . , X . . |
$$ | . . . O . O . . . . . . . . X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

As my discussion of the first problem suggests, the textbook play is the two space extension at , with the threat of .

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[go]$$Bcm15 Elf's top choice
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . . . . . . . . . . . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . a . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . b . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O , . . . . . , . . . . . , X . . |
$$ | . . . O . O . . . . . . . . X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

In its commentary, Elf preferred the 3d line attachment against the keima enclosure over the textbook play by 10½%. Elf has strong opinions, so I do not expect any other bot to have that large a preference, but I do think it will probably be substantial for that bot. It would not surprise me if another bot preferred to approach the White stone on the right side at or around a or b.

I don't think of the 3d line attachment as a non-human play. It was played in various contexts during the 19th century, and the bots may be bringing it back.

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[go]$$Bc Black to play
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O . . . . . . . . 3 . . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 2 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . a . . |
$$ | . . . , . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 1 . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . . O , . . . . . , . . . . . , X . . |
$$ | . . . O . O . . . . . . . . X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Speculatively:
Current position:
X. I thought it was white to move, and thought about the two space checking extension in the upper left at C13, aiming at C8. In the upper right, Q14 leaves a better connection but seems slack, so R14 seems more greedy. Perhaps R13 is proper. R5 seems premature to me but locally good. I also considered N17 to induce a response. Overall, C13 remains my favourite.
1. If B to play, the right is big but the groups are all fairly safe with no thinness to exploit. W has miai. On the left, B and W are close enough together that a W response in the upper left is big, while leaving B without a good move to defend.
2. I think the main static difference between C14 and C15 is the effect on the B15 area. Exchanging C14 for D15 is very good for B due to overconcentration with E17, apparently enough to offset the C15 for B16 (or D16) exchange.
3. In response to B[C15]W[B15] B has D16 with aji of B14 with a good two space extension to C11. As usual, white's main options to C15 are D16 and D15. This helps prevent W playing C13 in sente.
4. After B gets sente on the left, my instinct is to play on the upper side to reduce W's thickness but it depends. For example C15 D15 C14 B16 D14 E15 F13 instead comes to mind.

Past:
1. The lower left joseki is getting rare these days as the solid connection at D6 is preferred to the hanging connection at D7.
2. The white move wedging on the right seems a little strange, but probably a good move in the context of the right side.
3. The lower right shimari seems good when W is solid in the lower left. I marginally prefer it to a high enclosure or an enclosure pointing in the other direction.
3. Overall I feel black gains marginally on the left while the right side is even.

Check KG:
1. I don't think about F16 so much here since it seems split shape with left, but actually, I suppose it works when B has development on left and upper side.
2. On the right, extension from the 3-3 is preferred to from the shimari. I suppose W's lower left is too solid to develop a moyo from the lower right, while extension from the 3-3 defends a lonely stone.