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Tripod Group
Path: LifeAndDeath   · Prev: LongLGroup   · Next: JGroups
  Difficulty: Beginner   Keywords: Life & Death, Ko

Table of contents Table of diagrams
Tripod group
First attack
Still some aji!
Second attack
Alternate response?
Tripod group
Tripod group
What about this ?
KO
No ko. Alive.
Black's mistake
White creates the ko
Black cannot sagari.
The effect of the a-b exchange
This is unconditionally alive
This is unconditionally alive
This is unconditionally alive (Black 8 at 4)
What about?
One variation
Black dies
Black escapes but ...
Application
Invasion
Two points smaller corner

The tripod group

[Diagram]
Tripod group

The black group in this diagram is called tripod group. It is one of the smallest shapes in the corner that is alive as it stands. Black needs to remember the correct reply to two white attacks.


[Diagram]
First attack

This is the first attack. After B2, Black still has a live shape in the corner.



Alain : This is true in most positions, but Black should be careful when White plays in the neighbourhood!

[Diagram]
Still some aji!

One should keep in mind that a white move at one of the marked points threatens locally to kill the corner. Of course, White has to be very strong on the outside if she wants to play like this.



[Diagram]
Second attack

This is the second attack.


[Diagram]
Alternate response?

Shaydwyrm: I think this also lives, is there a disadvantage to it?



[Diagram]
Tripod group

How can Black defend against WC? --Stefan Verstraeten


[Diagram]
Tripod group

This move seems to work. a and b are miai, as are c and d. - Andre Engels


[Diagram]
What about this ?

[Diagram]
KO

[Diagram]
No ko. Alive.

SnotNose: The tripod group (in the surroundings shown) is unconditionally alive. If White a, Black b. If White c, Black d. B3 in the previous figure was a mistake.



The tripod group with the unneccessary exchange

[Diagram]
Black's mistake

In this context, Black must be careful not to make the 'sente' exchange as shown in this diagram.

The reason is that the status of the corner has now changed to ko. White can set up this ko following the next diagram.


[Diagram]
White creates the ko

Black is now forced to win the ko if he wants to keep the territory in the corner.


[Diagram]
Black cannot sagari.

Black cannot play descent at B2: W3 is the killing tesuji, making a placement and aiming at setting up a snapback at a. Black is dead.



[Diagram]
The effect of the a-b exchange

The a-b exchange creates a shortage of liberties. After W5 in the previous diagram, if Black hadn't exchanged a for b, he could live unconditionally.

--Alain Wettach



A variant of the tripod group

[Diagram]
This is unconditionally alive

[Diagram]
This is unconditionally alive

The throw-in at B4 is the key move. After B6, if White takes two stones at a, Black will take back the white stone at a.


[Diagram]
This is unconditionally alive (Black 8 at 4)

This variation with W5 taking the ko gives the same result as the previous diagram - unconditionally alive.

--unkx80



[Diagram]
What about?

We have practiced the tripod group at our club. In response to W1, B2 is the intuitive move for many players. We were wondering why this would be "wrong". I think that under these conditions, with all that open space around, this is actually a good move, but the tripod often appears in enclosed space, so that a white attachment at a becomes dangerous. Moreover, if there were an escape route along the left side, White would have blocked at B2 instead of W1. So, B2 at a is the main line.


[Diagram]
One variation

[Diagram]
Black dies

[Diagram]
Black escapes but ...

So, Black escapes, but loses his corner territory and, what's more important, his eye potential there.

--DieterVerhofstadt



Practical application

[Diagram]
Application

This is a position from the final game of the 2000 German Championship, between Franz-Josef Dickhut (Black) and Christoph Gerlach (White). Black wanted to do something about the upper left corner.


[Diagram]
Invasion

So he invaded at B1. White can play W4 one point higher, but then Black has a cut at W4, which he can use to isolate the two white stones at the top. Either way Black creates a nice position.


[Diagram]
Two points smaller corner

From an endgame point of view, it is better for White to play like this diagram: Black will end up with two points less in the corner. However in the game White followed the previous diagram, probably because he didn't like the remaining weaknesses on the left side following this sequence.



Path: LifeAndDeath   · Prev: LongLGroup   · Next: JGroups
This is a copy of the living page "Tripod Group" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.