Eight point Eye - Possible Ko

    Keywords: Life & Death, Ko
[Diagram]

White makes ko

Note: This line of play is usually not best for White. It is for demonstration purposes. An eight point eye is not enough to guarantee life.

Usually a is better for White than W3. Often it is right for Black to tenuki instead of playing at B2.

-- Bill Spight


Hmm, it looks to me like black can get a seki after W3 (B8 at B2):

[Diagram]

Black gets a seki



Alternately:

[Diagram]

Black gets a seki

Which is a way to get to Seki inside the bulky five, although it involves a 1-point mistake by White.

Presumably the seki is normally preferable to the ko for Black.

-- Evand


Bill: Oops! I analyzed this 9 years ago and had forgotten the niceties.

[Diagram]

White kills



Here is the main line:

[Diagram]

White makes mannenko


TJ Not sure if that one works, but I was working this up while Evand was editing...

Immediately re-edited and removed another diagram where black's play gets himself killed instead of a seki. The remaining one still looks good, though, no?

[Diagram]

Seki?

Bill: Black is dead.

grolich?: Just to make sure it is clear even for beginners why in this diagram black is just dead, and there is no seki (obviously whoever placed the diagram here thought that it was a seki):

We need to look at the matter from both sides, white and black. In the diagram, black can never capture white, since black cannot give atari, as that would put his own group in atari, and he would be captured.

However, from white's point of view, he can capture black whenever he wants. If white gives atari, he is NOT putting himself in atari, because he will have a second liberty in the corner.

So while it is true that black can never capture white, white can capture black whenever he wants. Therefore, the black group is dead as it stands.

For it to be a seki, it must hold true that neither side is able to capture the other.

ChrisSchack: Even if black WERE able to capture white when white moved to capture black, it's still perfectly killable ... it's only seki when you can't form a dead shape inside.


This is a copy of the living page "Eight point Eye - Possible Ko" at Sensei's Library.
(OC) 2008 the Authors, published under the OpenContent License V1.0.
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