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Problem 30 in "Life and Death: Intermediate Level Problems"
http://www.lifein19x19.com/viewtopic.php?f=15&t=4508		 Page 1 of 1
Author:  EricBackus [ Sat Aug 20, 2011 10:23 pm ]
Post subject:  Problem 30 in "Life and Death: Intermediate Level Problems"
Here is the problem:

Click Here To Show Diagram Code
[go]$$c Problem 30: Is White dead or alive?
$$ -------------------
$$ . . . . O . . . . |
$$ . . . X X O O 1 . |
$$ . . . . . X O . . |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


The book says:

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[go]$$c Problem 30: Alive
$$ -------------------
$$ . . . . O 6 . 3 . |
$$ . . . X X O O X 2 |
$$ . . . . . X O 5 . |
$$ . . . . X . O O 4 |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]
White can live in seki after this 2.


However, can't black do this?

Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . . 4 . |
$$ . . . X X O O X 2 |
$$ . . . . . X O . 3 |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


What am I missing?
Author:  Redundant [ Sat Aug 20, 2011 10:33 pm ]
Post subject:  Re: Problem 30 in "Life and Death: Intermediate Level Proble
Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . . 4 . |
$$ . . . X X O O X 2 |
$$ . . . . . X O . 3 |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . 7 4 5 |
$$ . . . X X O O X . |
$$ . . . . . X O 6 3 |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . 7 . 5 |
$$ . . . X X O O X . |
$$ . . . . . X O 6 3 |
$$ . . . . X . O O 8 |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


White lives in double ko.
Author:  Mef [ Sun Aug 21, 2011 4:11 am ]
Post subject:  Re: Problem 30 in "Life and Death: Intermediate Level Proble
Just for further study -- A related position
Author:  EricBackus [ Sun Aug 21, 2011 10:09 am ]
Post subject:  Re: Problem 30 in "Life and Death: Intermediate Level Proble
Redundant wrote:
Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . . 4 . |
$$ . . . X X O O X 2 |
$$ . . . . . X O . 3 |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . 7 4 5 |
$$ . . . X X O O X . |
$$ . . . . . X O 6 3 |
$$ . . . . X . O O . |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


Click Here To Show Diagram Code
[go]$$c Problem 30: Ko?
$$ -------------------
$$ . . . . O . 7 . 5 |
$$ . . . X X O O X . |
$$ . . . . . X O 6 3 |
$$ . . . . X . O O 8 |
$$ . . . . . X O X . |
$$ . . . . . X X X . |
$$ . . . . . . . . . |
$$ . . . . . . . . . |[/go]


White lives in double ko.

Thanks! This also answers my next question, which is how this differs from a similar position in Davies' "Life and Death", which is claimed to be a ko. The difference is that there is no extra liberty at Q16. Without that liberty, black could play 9 at T15 and white would not be able to make the double ko.

This all stems from my deciding that I want to understand the L+1 and L+2 groups better. As always seems to be the case in go, there is an awful lot going on if you look at it thoroughly. I keep thinking I should be able to get to where these shapes are like bulky five, where I just "know" the right answer and don't need to read. But I've got a long way to go.
Author:  Mef [ Sun Aug 21, 2011 11:36 am ]
Post subject:  Re: Problem 30 in "Life and Death: Intermediate Level Proble
EricBackus wrote:
This all stems from my deciding that I want to understand the L+1 and L+2 groups better. As always seems to be the case in go, there is an awful lot going on if you look at it thoroughly. I keep thinking I should be able to get to where these shapes are like bulky five, where I just "know" the right answer and don't need to read. But I've got a long way to go.


Not to promote shortcuts, or using memorized answers to avoid actually reading out positions but you can kinda think of it this way --

Remember the L group is dead (regardless of sente)...then thinking about what that implies...

Presumably, if you add 1 stone to it (L+1, or J group), now it lives or dies by sente....

Which means presumably, if you added 2 stones to it (L+2, or J+1) it should live even if your opponent has sente....

Of course hanes for black or descents for white can make it all the more tricky...
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