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RTGProblem4

 

RTG Problem 4 Attempts
   

BrianMarshall: Well, I guess I'll make an attempt.

[Diagram]
Diag.: White first to play.

To me, White 1 seems the best move at the vital point of Black. Even so, it seems black has the chance to live in ko.


[Diagram]
Diag.: Black gets ko, I

After Black 8, doesn't this depend on the ko?

unkx80: Nice try! Unfortunately the correct result is not ko. =)


Another attempt resulting in ko:

[Diagram]
Diag.: Black gets ko, II

White invades fiercely...


[Diagram]
Diag.: Black gets ko, II - moves 11-13

But after White 13, Black can again live by winning the ko. White 11 at 12, while tempting (to me, at least), is worse. Black 2 at 1 gives Black unconditional life.



Now an example of one failed attempt by White.

[Diagram]
Diag.: White fails

After Black 2, I think a and b are miai for life.

unkx80: This statement is somewhat inaccurate. White 3 at b, Black 4 at a, and White 5 at c makes a ko.

Brian: Ah, I see. Thank you for the correction.


[Diagram]
Diag.: White fails again

Now Black can easily get two eyes and live.

unkx80: If White 5 is played at 6, then Black dies. Also, what happens when Black 2 is played at 6?

Brian: Hmm. If White 5 is at 6, then Black cannot split at 5, or he'll lose the marked stone. But blocking reduces the eye to three in a row, which White can kill. Ok, I see that now.

But when Black 2 is at 6,


[Diagram]
Diag.: A better result?

White can just extend with 3, preventing an eye in the corner. Black needs an eye on the left, so Black 4. Ah! White 5 kills, then, by threatening a White move at 6. Black 6 defends, but White 7 prevents the eye.

Is this the correct answer this time?

unkx80: What if Black 4 is played at 6?

Brian: If Black 4 is played at 6, then White 5 played at 4 prevents an eye on the left.

Bill: But then the result is seki. :-)


[Diagram]
Diag.: Important plays

The situation after White 1.

In my mind, for Black to form an eye at z he needs to occupy one set of: a-b-c-d, a-b-c-e, a-b-d-e, or b-c-d-e.

Alternately, Black could attempt to form an eye at d. This would require points c-z-e.

Since, at best, Black requires three of six points, White can prevent this.



unkx80: I admit that this problem is not so easy, and this isn't the Beginner Exercises series. I shall drop one hint: the main line to the solution involves shortage of liberties. Good effort there! =)


[Diagram]
Diag.: Main line

Dieter: I have a feeling this is coming pretty close. Just another minute ...



[Diagram]
Diag.: Damezumari

In a real game I would have gone for ko, I'm afraid. :-(
B 8 cannot connect at 9, because of damezumari. W 9 takes away the second eye.

unkx80: Bingo. =)


Thanks for the hint, unkx80, I had been under the illusion that Black could connect at 9. ;-)




This is a copy of the living page "RTG Problem 4 Attempts" at Sensei's Library.
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