Some Repeating Go Positions

Ko is the main repeating position for which there is a specific rule to avoid the game going on forever. However, there are more complicated, and usually fairly rare positions which are repeating and for which in some rule sets special rules are needed to find a conclusion for a game. Some of these are shown here. The rules related to these differ between the major rule sets. Note that our official rules (based on AGA Rules) do not allow a repeated position with the same person to play.


ko diagram

Triple Ko

triple ko diagram

"Round Robin" Ko

'round-robin' ko diagram


cho-sei diagram

Molasses Ko

Note the occasional pass during this sequence
molasses ko diagram

Shimada's ko

Taken from this page by Harry Fearnley
Shimada's ko diagram

The molasses ko. T. Mark Hall writes:

The molasses ko (not my name for it) happened in a game at the old Central London Go Club between myself and a Chinese player whose name is Zhao. We used to play many games in an evening, very fast, with me usually winning. As far as I can remember it was on a Friday evening meeting in the winter of 1993/94. Mr Zhao gave up on the position and allowed his group to die, but it was sufficiently interesting for me to take to Maastricht to show to the pros to ask the status of the groups. James Davies was touring in Europe and I believed he saw it then and gave it the name. I also raised it with pros at the Nihon Kiin this year [1998].

The position is shown above.

At Maastricht the view appeared to be that it would be a seki. However, James Davies told me in Japan this year that, if it appeared in a game, it would be judged as a "no result". I believe that the thinking was that the player who finishes with the two-point eye space at the end of the game could claim that the other group was dead. Therefore neither side could afford to give up fighting the ko. At least one pro copied the position onto a record sheet, presumably for further study.

Note that the opinions mentioned above, on the status of the molasses ko, are in the context of Japanese rules. Other rulesets handle repeating positions differently.

T. Mark Hall appears to be mistaken in saying that the name "molasses ko" was given by James Davies. Fred Hansen claims that he was the first to use the term, in an article in the American Go Journal, sometime around 1996.

Last updated Tue Apr 25 2017.
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