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Is this seki?
http://www.lifein19x19.com/viewtopic.php?f=12&t=9126
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Author:  shunoshi [ Sat Sep 28, 2013 9:08 am ]
Post subject:  Is this seki?

Nice to see this place found a new home. I was a member of godiscussions.com years ago and thought the site was gone for good. I just have a quick question for those in the know.

Sometimes the concept of seki confuses me a bit. Is this seki? Part of me says it is, but part says it isn't.

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . . |
$$ . . X X X X X X |
$$ . X O O O O X O |
$$ . X X O . O O O |
$$ . X O O X X X . |
$$ ----------------[/go]


Thanks for the help.

Author:  xed_over [ Sat Sep 28, 2013 9:39 am ]
Post subject:  Re: Is this seki?

yes -- there are only two places either player can play. If white plays in either spot first, he will be in atari and be captured. White loses. If black plays in either spot first, he will be in atari and be captured and no longer able to cpture white at all. Black loses.

Since neither side can play first without losing, what you have then is a Mexican Standoff -- or seki.

Author:  Bill Spight [ Sat Sep 28, 2013 9:40 am ]
Post subject:  Re: Is this seki?

I take it that you understand why White cannot play atari. :)

Click Here To Show Diagram Code
[go]$$Bc Variation 1
$$ . . . . . . . . |
$$ . X X X X X X X |
$$ . X O O O O X O |
$$ . X X O 1 O O O |
$$ . X O O X X X 2 |
$$ ----------------[/go]


Click Here To Show Diagram Code
[go]$$Bc 2 eyes for White
$$ . . . . . . . . |
$$ . X X X X X X X |
$$ . X O O O O X O |
$$ . X X O . O O O |
$$ . X O O 3 4 . O |
$$ ----------------[/go]


If :b3: at 4, :w4: at 3.

Click Here To Show Diagram Code
[go]$$Bc Variation 2
$$ . . . . . . . . |
$$ . X X X X X X X |
$$ . X O O O O X O |
$$ . X X O 2 O O O |
$$ . X O O X X X 1 |
$$ ----------------[/go]


Click Here To Show Diagram Code
[go]$$Bc 2 eyes for White
$$ . . . . . . . . |
$$ . X X X X X X X |
$$ . X O O O O X O |
$$ . X X O O O O O |
$$ . X O O . 3 4 . |
$$ ----------------[/go]


If :b3: at 4, :w4: at 3.

¿Es claro? :)

Author:  shunoshi [ Sat Sep 28, 2013 10:13 am ]
Post subject:  Re: Is this seki?

Thanks guys. That pretty much confirmed what I had thought.

Author:  HermanHiddema [ Sat Sep 28, 2013 10:20 am ]
Post subject:  Re: Is this seki?

Note that this is seki even if white has outside liberties.

E.g if we change the position to this one:

Click Here To Show Diagram Code
[go]$$
$$ . . . . . . . . . . |
$$ . . . . . . . . X . |
$$ . . . . . . . . . . |
$$ . . . . X X X X X . |
$$ . . . X O O O O X O |
$$ . X . X X O . O O O |
$$ . . . . O O X X X . |
$$ ----------------[/go]


Now white could capture black if he wanted. But he would be left with a dead shape (see: http://senseis.xmp.net/?Nakade)

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