Long L group

    Keywords: Life & Death, Shape

Table of contents

The standard long L group

Chinese: 带钩 (dài gōu)
Japanese: 隅の八目形 (sumi no hachimokukei)
Korean: -

[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.

This shape is also sometimes referred to as The L group with 1 arm.


The long L group without outside liberties

Chinese: 紧带钩 (jin3 dai4 gou1)
Japanese: -
Korean: -

[Diagram]
The long L group without outside liberty  
[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.

Black should not play B6 at a because it results in a direct ko. The ten thousand year ko is much better for Black. Refer to that page for more detail.


The long L group without outside liberties, with hane on one side

[Diagram]
The long L group with hane one side  

When the black+circle hane stone is on this side, nothing changes. The sequence above still applies.

[Diagram]
The long L group with hane one side  

When the black+circle hane stone is on the other side, things get a bit more interesting.

[Diagram]
Ten-thousand year ko  

White can still get a ten-thousand year ko, but the sequence is now different.

[Diagram]
Black lives  

The usual clamp at W1 does not work. Thanks to the black+circle stone, B2 lives, and White cannot bridge under at a.


The long L group with an outside liberty

Chinese: 宽带钩 (kuan1 dai4 gou1)
Japanese: -
Korean: -

[Diagram]
Long L group 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 - B4 is the key move to remember, aiming to play at a...



[Diagram]
Variation 1: seki  

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



[Diagram]
Variation 2: still alive  

(B8 at 6)

The strongest attempt for White (if White must kill) is to play atari at W5 in this diagram. But Black sacrifies yet another stone at B6, and takes back with 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 at a, Black at b, it will be obvious that Black is unconditionally alive. The extra liberty comes in very handy here.


The long L group with a descent outside (1)

[Diagram]
Descent outside (1)  

White has descended to the edge with white+circle. If Black doesn't answer, he dies unconditionally.

[Diagram]
Descent outside (1)  

Black's attempt at a ko lacks liberties instead.

Note that W5 can also be played at W7.



[Diagram]
Hane outside  

Gokyo Shumyo, Section 1, Problem 18 / Solution includes this variation. black+circle creates a defect: now B4 is atari, making the previous diagram fail.



[Diagram]
Hane outside  

(W3 at white+circle)

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


The long L group with a descent outside (2)

[Diagram]
Descent outside (2)  

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



[Diagram]
Descent outside (2)  

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


See also


Long L group last edited by hnishy on July 13, 2018 - 18:50
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