BQM 251

    Keywords: Life & Death, Question
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black to play and live

xela: This is problem 334 from volume 4 of Graded Go Problems for Beginners.


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solution

This is the answer given in the book.


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can black live unconditionally?

My question is: what happens if white plays this way instead?

Now if black plays 'a', white replies at 'b' for ko. If black 'c' instead, then white 'd'. Does black have a better move?

Dieter: I can't refute it.


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Ko?

tderz: at present I see nothing better than a ko.
Sometimes black moves at d gain an edge by hampering white's underneath connection, but white seems to destroy then all the eyes from the left.
This ko B3 - B7 is a very bad ko for Black (White takes first)

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Ko?

tderz:


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the threat to escape

tderz: the threat to escape to the center/edge is usually understood as a solution for Life in TsumeGo.

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the threat to escape

Dave: B5 in the previous diagram looks like a mistake to me. Just extending to B1 seems to ensure life for Black.

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the threat to escape

HermanHiddema: Does this escape threat actually work? I think black will have to play B5 in the previous diagram one line lower to escape.


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Ko?

tderz: If White choses m, Black lives. White can also chose to fight for the ko-connection at n after B3 in the diagram below.
This ko is much better for Black as he took first.

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Ko?

tderz: Alleged internal ko threats black d+e do not seem to work, as White would connect the ko at W3 , then live with f.
Even if this life was not possible black needs too many approach moves (5 = g+h+f+c+i) while Black has only 4 liberties p-q-r-s on top.

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Ko? - Life! - dream sequence


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Ko?

tderz: Of course White connects the ko, lives herself and kills white.


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ko

tderz: Concluding from above, it seems that this ko has t be fought.

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ko

tderz: This is a good ko for Black as he took first.

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life from here

tderz: threatening with a only leads to ko b.
Connecting at b lives from here.

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life


Alainwettach: Maybe there is one other move to try

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What about this move?

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This seems to live without ko

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Also alive

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This is more complicated.. but also alive

Herman Hiddema: What if white plays W6 at B7?

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Good question! I think it is ko again

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So the proper order could be...

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But still, w 6 seems to give a ko

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So then it must be... double ko!

Alainwettach: in this variation, B seems alive with double ko if he throws in at a after w captures 9.

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What about this?

unkx80: Looks like a ko to me?


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char: Try here =)

Really, I am not joking.

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Herman Hiddema: This way, black wins the semeai, so apparently the marked move allows black to escape.

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Dave: I think there is no escape for Black here. Black still has only ko although a is now an internal ko threat for Black.

Herman Hiddema: B6 should be at B8, then black still wins the semeai

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Dave: Oops! You are right Herman.

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Dave: In theory White can still make ko with W7. But when White also has to play to stop the escape, Black ends up with a large number of internal ko threats starting with a.

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unkx80: To be pedantic, I would even say that Black can live by double ko. After B3, Black either wins the ko on the left side by capturing at a, or wins the ko on the right side by capturing at b and then c. Also, White d may be answered by Black e. (If W2 at B3, then Black plays at a for a snapback.)


This is a copy of the living page "BQM 251" at Sensei's Library.
(OC) 2014 the Authors, published under the OpenContent License V1.0.
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