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This tsumego problem
http://www.lifein19x19.com/viewtopic.php?f=11&t=10125
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Author:  cherryhill [ Sun Apr 06, 2014 6:05 pm ]
Post subject:  This tsumego problem

This is from the problems within the WBaduk client. Specifically this is question 190 from the 19k-15k set.

The problem asks for black life but I am confused how this isn't a dual life problem?

The answer is black S4 then white goes to R1 and black makes life by playing S2. I don't understand why white doesn't play S2 instead.



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tsumego.sgf [132 Bytes]
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Author:  moyoaji [ Sun Apr 06, 2014 6:17 pm ]
Post subject:  Re: This tsumego problem

You are correct that white S2 does lead to seki. In life and death problems, seki is usually seen as "good enough" for life. There are some problems that ask you to avoid seki, but in this case it seems fine. Black can't do better.

I don't see why white doesn't play that way. Either way white gets sente and this way black has the possibility of a half point ko for later.

Perhaps white fears that black will use the threat of ending the seki at R3 as a ko threat in some larger fight? But that would be a strange ko threat - you basically never want to do that.

Or maybe white wants the extra liberty at the 1-1 point for his outside wall?

It could also just be the variation the problem writers wanted to include. Maybe they thought seki wouldn't be a good answer for 19-15k players?

Author:  oca [ Sun Apr 06, 2014 11:02 pm ]
Post subject:  Re: This tsumego problem

:b1: at S4 is fine for me but I don't understand how :w2: at S2 would lead to seki ?
I would then play :b3: and that all over for white isn'it ...


Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X X |
$$ . . . O X 1 . |
$$ . . . O X . X |
$$ . . . O X 2 O |
$$ . . . O 3 O . |
$$ --------------[/go]

Author:  moyoaji [ Sun Apr 06, 2014 11:04 pm ]
Post subject:  Re: This tsumego problem

oca wrote:
:b1: at S4 is fine for me but I don't understand how :w2: at S2 would lead to seki ?
I would then play :b3: and that all over for white isn't it ...
Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X X |
$$ . . . O X 1 . |
$$ . . . O X . X |
$$ . . . O X 2 O |
$$ . . . O 3 O . |
$$ --------------[/go]

Can black put white in atari to capture him?

Author:  oca [ Sun Apr 06, 2014 11:20 pm ]
Post subject:  Re: This tsumego problem

moyoaji wrote:
oca wrote:
:b1: at S4 is fine for me but I don't understand how :w2: at S2 would lead to seki ?
I would then play :b3: and that all over for white isn't it ...
Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . . . . |
$$ . . . . O O O |
$$ . . . . O X X |
$$ . . . O X 1 . |
$$ . . . O X . X |
$$ . . . O X 2 O |
$$ . . . O 3 O . |
$$ --------------[/go]

Can black put white in atari to capture him?


:blackeye: of course he can't :oops: ... seky... or maybe...
Click Here To Show Diagram Code
[go]$$Bc
$$ . . . . 5 7 9 |
$$ . . . 3 O O O |
$$ . . . 1 O X X |
$$ . . 8 O X X . |
$$ . . 6 O X . X |
$$ . . 4 O X O O |
$$ . . 2 O X O . |
$$ --------------[/go]


but that would happend only if I'm white :D

Author:  Hushfield [ Mon Apr 07, 2014 5:23 am ]
Post subject:  Re: This tsumego problem

This problem is also featured in Lee Changho's Life and Death series, vol.1, problem 37 on pp.75-76. The solution given there is the same as the one proposed by the WBaduk client. If anyone can read Chinese, you might find more on this in the book.

The variation leading to seki is one point better for white, and white retains sente in both variations, so I don't understand why the authors would choose this variation.

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