Joseki-related life-and-death example 1

    Keywords: Joseki, Life & Death

Joseki

[Diagram]
Joseki.  

This is a common 4-4 point enclosure joseki.

[Diagram]
Joseki.  

W1 can also be played at a. In fact, it is the most common reply in professional games.

W3 can also be played at b.

B4 ends the joseki.



Discussion I

[Diagram]
White is alive.  

The group in the corner is alive, as discussed in L+2 group.

However, a black descent at a is sente.[1]

[Diagram]
Ko.  

If White tenukis, Black can start an approach ko with the sequence from B1 to B5.

[Diagram]
Dead.  

The atari at W4 is a mistake. After B7, white is caught in a shortage of liberties and is unable to play at a.



Discussion II

[Diagram]
dia 1: White is alive.  

Dia.[1]: In this diagram, White is alive too. (See J+1 group.)

However, the descent at a is sente.[2]

[Diagram]
dia 2: Dead.  

The throw-in at B1 followed by the placement at B3 is the tesuji. After which, a and b are miai, while c and d are also miai. White dies in a bent four in the corner dead shape.


Author:


[1]

I'll comment that, because Black's threatened ko is indirect, one cannot assume it is really sente until the latter stages of the game. This may affect fighting on the outside.

Charles

[2] Note however that it is usually an endgame mistake to play the descent. Instead, Black should start at b.

Bildstein: That's very interesting. Can anyone explain why?

[Diagram]
dia 3: Black starts with a  

tderz: White will have about 5-6 points. (depending on the timing of the n-m-p exchange).

Black ends in sente.

[Diagram]
dia 4: Black starts with b  

tderz: White will have about 4-1=3 points or less (depending on the timing of the n-m-p exchange).

Black ends in gote.

Conclusion: starting with b in dia.[1] seems to be about 2 points better for Black, and it seems to me that Black is relatively free to chose when to play, because White has no sente variation herself for improvement.

I hope that no errors crept in.


Joseki-related life-and-death example 1 last edited by 68.99.65.50 on August 20, 2012 - 22:03
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