Quintuple Ko

  Difficulty: Expert   Keywords: Ko

A Quintuple Ko is an extremely rare situation in which there are five interrelated kos, and a resulting cycle of ten moves, which will result in a void game under some rules, or in a complicated ko fight under others.

Example

There is no known example from professional play, but it is rumoured to have occurred in amateur play in Japan.

An example from actual play would be most welcome.

For an example, see [ext] Quintuple Ko.

Constructing an example

Attempts welcome.

[Diagram]
Black to play  
[Diagram]
Quintuple ko  

With the moves B1 - W5, the position has reversed to the next diagram.

[Diagram]
Quintuple ko, white to play  

This is symmetric with the previous diagram, so white start another series of 5 moves to return to the original position.


If Black does not play take a ko, white wins:

[Diagram]
Attempt at Quintuple ko  

Now, black is dead, because even if black retakes at black+circle, white can take at white+circle as an internal ko threat.


Quintuple Ko last edited by 80.101.109.117 on August 2, 2013 - 01:33
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