HermanHiddema/OGS Triple Ko analysis

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[Diagram]

Assuming the game finished like this, and now both players pass.

What is the status of black and white in the lower right, given Japanese rules?

[Diagram]

Reference diagram

Under Japanese rules, during the determination of life and death, neither player may ever retake any ko unless he has passed for that specific ko ([ext] Japanese rules section 7.2)


If black tries to prove that white is dead, play goes as follows:

[Diagram]

Black tries

After B3, white cannot retake at white+circle, due to the aforementioned extra rule. Given that the whole white group is in atari, white therefore cannot avoid capture.


If white tries to prove that black is dead, play goes as follows:

[Diagram]

white tries

W3: White passes to be allowed to recapture at white+circle

B4: Black passes to be allowed to recapture at black+circle

This can go on indefinitely, therefore white cannot capture black.


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