KyuExercise40/Attempts

Sub-page of KyuExercise40
[Diagram]

Black to play and live. No seki.

impu1se: I think this is right. White must play to keep black from making an eye. Black will now live due to the double ko. However, white has a nice source of ko threats.

IlyaM: Yep, this is correct solution. Playing B7 before B5 also works. Fortunaly in my game where this position appeared it appeared very late in the game so there was no ko-fights.

[Diagram]

Black to play and live. No seki.

EricBackus: I'm missing something. At any given move, black will hold either the 'a' ko or the 'b' ko, and white will hold the other.

If white is allowed to play 'c' and 'd', then this reduces to Double Ko Seki (right?) which we're told is a failure. To prevent this, black must take 'd'. But to do that requires winning a ko fight. It seems to me that black gets to choose between double-ko seki and a single-ko fight, and we're told that seki isn't good enough so this must be a single-ko fight. Is this really the best solution available to black?



[Diagram]

Another way

[Diagram]

continue

if white play at B2, black W1 live.

EricBackus: Wait, if white plays B2 and black plays W1, then if white plays at 'c', isn't that seki, and therefore a failure for black?

[Diagram]

if White a...

[Diagram]

Black Live. No seki

[Diagram]

if White b... still the same

W3 can also play at c, but no difference made.


- billyswong


EricBackus: I must be missing something obvious in the above two diagrams. Can't white play 'c', putting black in atari, and this reduces to a ko for life in the corner? So it's not life, it's ko, and thus a failure if unconditional life was possible?


[Diagram]

Another way for White

Bill: Through W6 the result is seki.



[Diagram]

This should do it

Black as to accept the loss of the two BC, and white should be happy playing a. If so black makes eyes at c. If white is determined and plays at b or c black connects at a with two eyes.

[Diagram]

like so

[Diagram]

White plays b

White b is a mistake

[Diagram]

White plays a c

so is white c. If white plays B5, black plays W4.


This is a copy of the living page "KyuExercise40/Attempts" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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