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LifeAndDeath

Referenced by
LGroup
TenThousandYearKo
KanazawaSolution18
KanazawaProblem20
KanazawaProblem20B

 

Long L -group
Path: LifeAndDeath   · Prev: L2Group   · Next: TripodGroup
    Keywords: Life & Death, Shape

[Diagram]
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]
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]
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]
Black can answer at 4

The attack by W1 and W3 fails. Black has an excellent way to live - by playing at B4, aiming to play at a...


[Diagram]
Variation 1: seki

If White answers at W5, Black will play at B6. The result is a seki - the same as living unconditionally when considered in terms of life and death.


[Diagram]
Variation 2: still alive

(Black 8 at 6)

The strongest attempt for White is to play atari at W5 in this diagram. But B6 sacrifies yet another stone, and takes back at B8...


[Diagram]
Variation 2a: oiotoshi

If White plays at W9, B10 will cause White to be caught in a connect-and-die (a kind of shortage of liberties).


[Diagram]
Variation 2b: big capture

W9 here won't start a ko either. After B10, White a, Black b, it will be obvious that Black is unconditionally alive. The extra liberty comes in very handy here.



[Diagram]
White descends to the edge (1)

White with WC has descended to the edge. If White plays first, Black is unconditionally dead.


[Diagram]
White descends to the edge (1)

Black's attempt at a ko lacks liberties instead.

Note: W5 can also be played at W7.


[Diagram]
White descends to the edge (1, variation)

Kanazawa Solution 18 includes this variation. BC creates a defect, and now B4 is atari making the previous diagram fail.


[Diagram]
White descends to the edge (1, variation)

(W3 at WC)

Subsequently, if White plays at W1, Black lives with B2 and B4.


[Diagram]
White descends to the edge (2)

White descends the other way. It is still the case that White to play can kill Black unconditionally.


[Diagram]
White descends to the edge (2)

This is also shortage of liberties. Black can't play at a after W7.



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Path: LifeAndDeath   · Prev: L2Group   · Next: TripodGroup
This is a copy of the living page "Long L -group" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.