Practical Endgame Test 1 / Solution 3

More analysis of "Practical Endgame Test 1".

Solution is White wins by 4 points - find it at Practical Endgame Test 1 / Solution.

Can Black keep the margin to 3?  

When Arno posted this position, I became fascinated by the question can Black force a better result than W+4? It took me a long time to think that I found the answer... --DaveSigaty

Variation 1  

Black plays B1 because otherwise White's play at b is too damaging. White then goes back to W2, giving Black the chance to capture at B3. If White now plays on the left, Black plays B5 forcing W6. White can not ignore B5 because Black at W6 followed by descending to the edge is a very big play (even bigger than capturing the black+circle stones if White plays at d instead of W6).

On the left side, Black at B7 is the right way to play. When White cuts at W4 it is worth 2 points for Black to ensure an eye on the left side. Otherwise he will have to play another stone on the right to prevent White's atari at c.


Black has two poins on the left and 10 points on the right.
White has four points at the bottom and 11 points at the top.
White wins by 3 points.

(NB: don't forget to count the captured stones.)

Variation 2  

White can try blocking at W4, knowing that she can win a ko fight. However, Black does not need the ko to improve on the solution diagram...

Imperfect reversion  

Now note that if White captures at a and connects, we have reverted to the solution diagram except that white+circle has been added inside White's territory. In addition each side has captured one stone near a but they offset each other. Final result? W+3.

Variation 3  

White plays W2 after reading out that she can't let Black capture here. However, B3 is a big play with the follow-up at B5 as absolute sente. Play continues to W10 but White's winning margin has been reduced to a single point.

To summarize: if White plays white+circle in the first diagram Black can force a three point loss, instead of the four point loss in the correct solution.

Practical Endgame Test 1 / Solution 3 last edited by CharlesMatthews on June 24, 2003 - 07:39
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