Some Endgame Problem 1 / Solution

Sub-page of SomeEndgameProblem1
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the problem

This is the position that was put forward in Some Endgame Problem 1.

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The cut does not work

The cut does not work in this case. Because her string is one stone longer, White can give atari at W4, and after W6 Black has achieved nothing.

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TuRen?'s variation

As TuRen? correctly stated, the above is wrong. Black can cut at B1, provided W2 is answered at B3. If White answers at W5, Black plays at B4 and gets a ko. If White answers at W4 or W6, this variation occurs. Black captures two stones in sente, exactly the same result as in the 'correct' variation below. In fact, this variation is even better than the one below because White's corner is worth 4, rather than 5, points.

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Not a vital point

B1 here also does not work. Again, Black does not get much for his trouble.

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Tesuji

The cut at B1 is tesuji. If White answers at W2, the moves to B5 give Black a ko.

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Even worse

If White connects after B3, she is unconditionally dead.

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White connects

If White connects at W2, she is dead too.

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Atari

And if White plays atari with W2, it is ko again (White a is a ko threat, forcing Black b).

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White's best move.

White's best move is W2. After this, White is unconditionally alive, but Black can capture two stones in sente with B3. (W6 is necessary because a black stone at the same point would kill the white group with a snapback).

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My blunder



Unfortunately, in the game where this position occurred (it was in the last round of the preliminaries for the 2001 Dutch Championships, against Marcel Bloemena), I did find B1, and my opponent did find W2, but I missed the black move at W6 in the previous diagram, and thus thought it would be gote. To avoid this result, I played the terrible move at B3, expected White a, Black b and White c (which would be 1 point better than the previous diagram), but of course my opponent answered at W4, after which I could not capture the two stones at all - not even in gote.

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Not as good

Instead of W2 in the last two diagrams, the atari here is also possible, but it is not as good. As shown before, Black plays at B3, but White avoids the ko with W4. Now White has only 4, rather than 5, points.

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Reference diagram

After BC, White will have to to play inside because Black threatens a double snap-back.

Charles I've added this diagram to make it clear that Black threatens an atari, leading rather to a combination of snapback and a connect-and-die.

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Furthermore...

Furthermore, Black can decide to play B5 on this side. Now White saves the two stones, but loses the other two. Furthermore, her territory has shrunk to 3 points only.

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Also incorrect

For Black to play at B1, which might look like a vital point, directly, without playing either cut first, also does not work. White connects at W2, and Black can still capture the stones: but only in gote.

-- Andre Engels


This is a copy of the living page "Some Endgame Problem 1 / Solution" at Sensei's Library.
(OC) 2005 the Authors, published under the OpenContent License V1.0.
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