Enclosing seki

    Keywords: Life & Death

Many usual seki positions contain at least two cuts (one or more of which may be a virtual cut beyond the edge).

However, there are sekis without any cut, too. Here you can find an (barely usual) example:

[Diagram]

enclosing seki

-- rubilia


Alex Weldon: I disagree with your statement that most sekis involve one or more cuts. Actually, enclosing seki are probably the more common variety. They can occur when the enclosing group cannot capture because of shortage of liberties or when the enclosing group cannot capture, because it would leave a dead shape AND the inner group cannot almost fill without leaving a live shape. Both of these varieties are probably most common in the corner. Simplest examples:

[Diagram]

Type A (shortage of liberties) Enclosing Seki

[Diagram]

Type B (dead shape) Enclosing Seki

I guess the biggest difference is that the shortage of liberties variety (which, one might note, all cutting sekis are) can be used as ko threats by either player. The dead shape variety cannot, except: a) if there are two inside and no outside liberties (in which case you can consider it a special seki of both types, and only the player of the inner group can use it as a ko threat) or b) if there is some semeai or other seki going on outside (in which case one or the other, or either player may use it as a ko threat, depending on the circumstances).


Yeah, cutless sekis probably aren't all that rare. I've adjusted the wording a bit. At first glance, the edge generally appeared as a cut to me, but I see that it simply works as a mirror instead. A group that has no real cut on the board doesn't have a virtual cut beyond the edge, either. I hope, Cut Beyond the Edge once will make clear what I mean. -- rubilia


(See also: CuttingSeki.)


This is a copy of the living page "Enclosing seki" at Sensei's Library.
(OC) 2009 the Authors, published under the OpenContent License V1.0.
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