Hol Igor Explores Yose Problem 1

  Difficulty: Advanced   Keywords: EndGame, Ko
[Diagram]

Find the value of Black 1

When is fighting this ko is favourable? It is quite large[1] as both opponents can end the fight by capturing another stone.

[Diagram]

Black wins everything

Black has 5 points + 2 captured stones. White has 6 points + 1 captured stone. The score is 0.



White has two plays elsewhere as compensation.

[Diagram]

White wins

Black has 1 point. White 9+2. The score is -10.



Black has a move as the compensation.


[1] Bill: After B1 the ko is indeed large. Typically, B1 is not good. But when Black is komaster he can pick up 2/3 of a point in two net plays by the following sequence:

[Diagram]

When Black is komaster

B3 - W4 = ko threat and response, B5 takes ko.

After B7 Black wins the corner ko.



If White plays first she gains 1/3 of a point with W1.


Thanks, Bill. So, the value of this position is not large. This settles it. I can now proceed to the next typical position.


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(OC) 2007 the Authors, published under the OpenContent License V1.0.
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