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 Post subject: James Davies - life and death - question
Post #1 Posted: Sat Nov 25, 2017 2:00 am 
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Greetings,

I have a question about one of the diagrams from the book of James Davies - Life and Death.

Dia4 on the pic below. Why is why alive? Doesnt white need to capture the 3 black stones inside in order to try to make 2 eyes - meaning capturing 3 stones is a dead shape?

Or black must first try to capture white?

Image

This really got me confused for some basic principles which I thought i knew :scratch:

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 Post subject: Re: James Davies - life and death - question
Post #2 Posted: Sat Nov 25, 2017 2:35 am 
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White must not actually capture (take off the board) the three Black stones, otherwise Black will respond by playing in the middle of where his three stones were, thereby killing White by reducing him to one eye.

As it stands, both White and Black share two liberties. White cannot capture Black for the reason stated above, but equally Black cannot capture White because when Black fills one of the two inside shared liberties, White will capture four stones and Black will have no way to reduce this shape to one eye.

So the best course of action for both players is not to play inside that shape. That means both are alive and both have 0 points in that area. This is called "seki". At the end of the game, the area will be left as is.

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 Post subject: Re: James Davies - life and death - question
Post #3 Posted: Sat Nov 25, 2017 2:53 am 
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Thanks for the answer. Then it is just an error in the book? Cause at the end of the explaination of Dia 4 the authos says "white is alive", and not "white is alive in seki".

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 Post subject: Re: James Davies - life and death - question
Post #4 Posted: Sat Nov 25, 2017 3:00 am 
Lives in gote

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Korulez wrote:
Thanks for the answer. Then it is just an error in the book? Cause at the end of the explaination of Dia 4 the authos says "white is alive", and not "white is alive in seki".


"White is alive in seki" would make it clearer, but generally, "is alive" covers "is alive with points" as well as "is alive without points" (i.e., seki).

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 Post subject: Re: James Davies - life and death - question
Post #5 Posted: Sat Nov 25, 2017 3:05 am 
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Thanks! It just a bit confusing cause later in the book at other examples the author uses "white/black is alive in seki".

I think the topic can be closed now. Thanks again for the replies.

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Post #6 Posted: Sat Nov 25, 2017 4:56 am 
Judan
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Quote:
"is alive without points" (i.e., seki).
Seki can have points in area scoring.

I don't know a 'formal' definition of alive;
I wonder about: "impossible for the opponent to remove from the board, given perfect play by both sides"... ? But maybe that's cyclical if a definition of 'perfect play' involves including seki.

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