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HitachiNumber9

 

Hitachi Number Nine Solution
    Keywords: Problem, Tesuji

Here is published problem solution for Hitachi Number 9


[Diagram]
Diag.: black to play.

After black 1, A and B are miai.


[Diagram]
Diag.: variation 1

In this variation, white can not play at C because of a shortage of liberties.


[Diagram]
Diag.: variation 1

FCS: After black 5, are blacks stones sufficiently saved?

Jonathan Cano: Yes. next diagram...


[Diagram]
Diag.: variation 1

Once black connects the square marked group to the cirle marked stone white can not keep these stones from escaping into the middle of the board where they can (presumably) link to a strong black group or make two eyes.

Thanks for the comment. I'll amend the original problem to include this assumption.



The following variation aroused a bit of debate in reg.games.go. Apparently the published solution did not show how to continue after black 3...


[Diagram]
Diag.: variation 2

How should black continue? He must not let white to play A and B or else black will die. Black can keep white from connecting by playing at A, B, or C. C is my current preference:


[Diagram]
Diag.: one possibility

This sequence is not so straightforward. See below (Dieter 2k).


[Diagram]
Diag.: continuing ...

[Diagram]
Diag.: continuing 2

With black 5, black captures the marked white stones. If white playse 4 at 5 ...


[Diagram]
Diag.: white's left side dies

White's marked group only has 6 liberties while black's marked group has at least 7

Can anyone improve on this?

  Jonathan Cano



[Diagram]
Diag.: "one possibility" - Dieter continues

This sequence is confusing: Move number 9 prevents White from playing at A in sente, but lets white live with 10. Black could kill White by playing at 10 himself.


[Diagram]
Diag.: "one possibility" - cont.

White 2 makes one eye and now threatens the connection at A or the second eye at B. However, she has a weakness at C, as shown.


[Diagram]
Diag.: "one possibility" - white prevents the cut

Black 1 prevents the connection. White now has to patch up the aji of Black A and plays kaketsugi?at 2. Black plays 3 to reduce White to one eye and he wins the semeai.


[Diagram]
Diag.: "one possibility" - white makes life

White still makes shape up to 8. Of course, Black's better off, splitting the two White groups.


[Diagram]
Diag.: white makes life AND takes the outside

And yet another possibility ...


[Diagram]
Diag.: white makes life AND takes the outside

... a complicated fight.


A second possibility


[Diagram]
Diag.: Second possibility

That's why IMHO Black 5 is a better answer: after Black destroys White's eye shape with 9, white A is no sente for connection anymore. White A and B are miai killing the white group:


[Diagram]
Diag.: Second possibility - a capturing race

[Diagram]
Diag.: Second possibility - a capturing race

[Diagram]
Diag.: Second possibility - a capturing race, 6 at 1

White is 5 liberties down in this capturing race.



The above demonstrated that White A is an overplay. So, White captures at 1, Black 2 recaptures at the marked spot ...


[Diagram]
Diag.: variation 2 - continuation

[Diagram]
Diag.: variation 2 - continuation

White 3 recaptures yet again - it's not a ko - and her stones are all connected. Although the marked white stones in the corner are dead, white still has the aji of the ogeima at B, so Black's corner is not too big. In the "capturing race" diagrams, White loses a lot of points compared to this diagram.

--DieterVerhofstadt



This is a copy of the living page "Hitachi Number Nine Solution" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.