RTG Problem 24 / Solution

Sub-page of RTGProblem24

Common pitfall

Common pitfall.  

A common pitfall is to play the descent at W1, assuming that capturing at a and the connection at W3 are miai.

Common pitfall. (6 at marked stone)  

This problem is deliberately set up in such a way that capturing the four Black stones directly does not live - it is a pyramid four big eye.

Common pitfall.  

However, one should notice that if the white+circle stone (which was W1) is at a instead, then White at b can make the second eye and live. This observation leads to the improved sequence below.

Improved sequence

Improved sequence.  

An improved sequence is the diagonal at W1, threatening a connection at B2 as well as a ko at W3.

Improved sequence (7 at marked stone)  

If B4 does not play the ko and destroys the eye at the side instead, then W5 is sente, so White has time to live at the vital point of W7. However, the improved sequence is not yet the solution, since Black takes the ko first.



White makes a throw-in at W1 followed by an atari at W3. Observe that B4 cannot connect at W1.


If B4 insists on killing the White group, then W5 takes the ko first. From the usual life-and-death perspective, this is the best play by both players.

If Black avoids this ko, White can live, as the variations below show.

Variation 1a  

Black may try this way after W1 takes the ko.

Variation 1b  

Must White fight this ko to live?

Variation 1c  

B4 at white+circle.

White can play this way.

Variation 1d  

B1 goes all out to kill.

W2 takes four stones, but cannot make an eye there because of under the stones play.

Variation 1e  

But White takes sente and lives.

Variation 2a  

Backing up, Black can do no better than B1, allowing W2 to live.

Solution (practical)  

Since this ko is so large, it is reasonable to assume that neither player has a ko threat, and also that the temperature of the board is not too high, so that there will be no ko exchange. Then the best way for Black to play is to simply capture at B4, allowing W7 to connect to the group outside.

Bill, unkx80

RTG Problem 24 / Solution last edited by Unkx80 on October 30, 2005 - 18:11
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