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Aliases (info)
LongLGroup

Paths
LifeAndDeath

Referenced by
TenThousandYearKo
OldMetaDiscussion
KanazawaProblem20
KanazawaSolution18

 

The Long LGroup
   

[Diagram]
Diag.: The long L-group

The black shape in this corner is the long L-group. It controls more corner space than the L-group, and this greatly improves its chances for survival.


[Diagram]
Diag.: a strange ko

This is White's best attack. She produces a somewhat strange ko in the corner. This is known as a Ten Thousand Year Ko...



[Diagram]
Diag.: With an extra liberty

This diagram is a modified one with extra liberty at 'a' for the black group. Note that black is unconditionally alive.


[Diagram]
Diag.: Black can answer at 4

The attack by white 1 and 3 fails. Black have an excellent way to live - by playing at 4, aiming to play at 'a'...


[Diagram]
Diag.: Variation 1: Seki

If white answers at 5, black will play at 6. The result is a seki, which is considered the same as living unconditionally when considered in terms of Life And Death.


[Diagram]
Diag.: Variation 2: Still alive

The strongest attempt for white is to atari at 5 in this diagram. But black 6 sacrifies yet another stone, and takes back at 8...

(black 8 at 6)


[Diagram]
Diag.: Variation 2a: Connect-and-die

If white plays at 9, black 10 will cause white to be caught with a connect-and-die. (Should this be termed Damezumari for white? --StormCrow
Yes. :-) --BillSpight)


[Diagram]
Diag.: Variation 2b: Big capture

White 9 here won't start a ko either. After black 10, white 'a', black 'b', it will be obvious that black is unconditionally alive. The extra liberty comes in very handy here.



[Diagram]
Diag.: White descended to the edge (1)

There is an extra marked stone that has descended to the edge. White plays first, and black is unconditionally dead.


[Diagram]
Diag.: White descended to the edge (1)

Black's attempt at a ko becomes a damezumari instead.


[Diagram]
Diag.: White descended to the edge (1 var)

KanazawaSolution18 includes this variation. The marked black stone creates a defect, and now Black 4 is atari making the previous diagram defunct.


[Diagram]
Diag.: White descended to the edge (2)

White descends the other way. Still, white first will kill black unconditionally.


[Diagram]
Diag.: White descended to the edge (2)

This is also damezumari. Black can't play at 'a' after white 7.



Authors:
--Stefan
--unkx80
--Dieter



This is a copy of the living page "The Long LGroup" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.