The game is GoGoD 2003-02-19g, the 4th game of the Kisei final between O Rissei (W) and Yamashita Keigo.
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[go]$$Bcm15 Thick and slow
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . a . . . . . . . . . . . . . |
$$ | . . 2 , O . . . . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X W W . . . . . . . . . . . . |
$$ | . . X . X 1 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Yamashita's
![black 15 :b15:](./images/smilies/b15.gif)
was new to me. When I was learning go,
a was the tesuji to know, played as a sacrifice to weaken or even capture the
![white with circle :wc:](./images/smilies/wc.gif)
stones. Elf reckons that
![black 15 :b15:](./images/smilies/b15.gif)
loses 15½% to par, while
a loses only 15%.
![Shocked :shock:](./images/smilies/icon_eek.gif)
The correct answer is none of the above. O replied with
![white 16 :w16:](./images/smilies/w16.gif)
securing the corner and threatening the Black group. Elf reckons that
![white 16 :w16:](./images/smilies/w16.gif)
loses 18½% to par!
- Click Here To Show Diagram Code
[go]$$Wcm16 Mainline for ![white 16 :w16:](./images/smilies/w16.gif)
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , O . . . . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X O O . . . . . . . . . . . . |
$$ | . . X . X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . W . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . b a . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 9 . . . . . . . . . . . . . . . . |
$$ | . . 1 6 . . . . . . . . . . . . . . . |
$$ | . 5 4 7 3 . . . . , . . . . . O . . . |
$$ | . . 8 X . 0 . . . . . . . 2 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
![white 16 :w16:](./images/smilies/w16.gif)
approaches the bottom left corner, with
![white with circle :wc:](./images/smilies/wc.gif)
as backup.
![black 17 :b17:](./images/smilies/b17.gif)
approaches the bottom right corner. (
a and
b are also playable, in order of preference.)
![white 18 :w18:](./images/smilies/w18.gif)
plays the press.
![black 19 :b19:](./images/smilies/b19.gif)
does not crawl on the 3d line, but resists. An AI joseki follows.
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[go]$$Wcm26 Mainline for
, continued
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , O . . . . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X O O . . . . . . . . . . . . |
$$ | . . X . X X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . 5 7 . . . . . . . . . . |
$$ | . O X O O 1 3 4 6 8 . . . . . O . . . |
$$ | . . X X . X 2 . . . . . . 2 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
White pushes to build a wall in exchange for territory.
Better play for
![black 15 :b15:](./images/smilies/b15.gif)
. Enclose the bottom left corner.
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[go]$$Bcm15 The Black group is OK.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . b . . . . . |
$$ | . . . , O . . . . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X O O . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 a . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Elf's top choice is to play the large knight's enclosure of the bottom left corner, with
a in second place, and certainly playable. No other play is on Elf's radar, i.e., gets more than 1.5k rollouts. I would not be too surprised if another top bot chose
b. In any event, it is not urgent to do anything about the Black group in the top left corner.
- Click Here To Show Diagram Code
[go]$$Bcm15 Mainline for ![black 15 :b15:](./images/smilies/b15.gif)
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . 3 . . 2 . . . . . |
$$ | . . . , O . . 4 . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X O O . . . . . . . . . a . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
This same position occurs in GoGoD 2000-01-29b, between Cho Chikun (W) and Kataoka Satoshi. I chose to use its variations, as they have many more rollouts (26.4k) than those in the O vs. Yamashita game.
After
![black 15 :b15:](./images/smilies/b15.gif)
encloses the bottom left corner, the top right corner becomes important. (White could also approach at
a.)
![white 16 :w16:](./images/smilies/w16.gif)
approaches from the top side,
![black 17 :b17:](./images/smilies/b17.gif)
pincers, and
![white 18 :w18:](./images/smilies/w18.gif)
bolsters White's position there, in a nice flow of the stones.
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[go]$$Bcm15 Variation 2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 6 8 . . . . . . . . . . . . . . . . |
$$ | . 3 7 O . . . 9 . . . . . . . . . . . |
$$ | . . . , O . 0 . . , . . . . . X . . . |
$$ | . . X . O X . . . . . . . . . . . . . |
$$ | . . . . X O O . . . . . . . . . . . . |
$$ | . 5 X . X . . . . . . . . . . . . . . |
$$ | . . 4 . . 2 . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Starting with
![white 16 :w16:](./images/smilies/w16.gif)
White boxes Black in, but then
![black 23 :b23:](./images/smilies/b23.gif)
gets to play on the top side with sente. Not that getting boxed in is good, but in exchange Black gets
![black 15 :b15:](./images/smilies/b15.gif)
and takes sente.