Cycle / Discussion

Sub-page of Cycle

RobertJasiek: Several years ago, in the mailing list go-rules, John Tromp found cycles of lengths 5 and 7 with the functional sequences kkkkkp and kkkkkkkp. Does anyone recall the shapes?

Herman: Interesting! Isn't there a mailing list archive?

RobertJasiek: Precisely, there is none (yet). I have a good percentage stored somewhere locally but no time yet to publish it as an archive.

Herman: I assume that terminology here is: k = ko, p = pass? Where ko means basic ko?

RobertJasiek: Yes, for the moves, and in square brackets, but I cannot denote the brackets on Sensei correctly or is there an escape character?

Herman The character ! escapes wiki syntax, so ![kkkkkp] will give: [kkkkkp]


Herman Hmmm, correct me if I'm wrong, or misunderstand, but if k = basic ko, then every k in the sequence should add one exactly stone and remove exactly one stone? So kkkkkp would:

  • add black, remove white
  • add white, remove black
  • add black, remove white
  • add white, remove black
  • add black, remove white
  • pass

And would have an unbalanced number of additions/removals, leading to one extra black and one less white? (ie: cannot be a cycle)

RobertJasiek: k means ko (in general) - not (necessarily) basic ko (as currently on Sensei's ko page). Sorry, overlooked your earlier question related to basic ko.

Herman: Ok, thanks. Can you clarify for me: k refers to any play on a ko intersection? ie: the 5 move cycle currently named sending three returning two qualifies for the pattern [kkkkkp]?

RobertJasiek: Yes. Or use [kkkkkt] in case of a tenuki.

ThorAvaTahr: Would it even be correct to say that any cycle of length 5 would be [kkkkkp]?

Herman: I can imagine there might be cycles that include (necessary) suicide, don't know if any of them could be 5 long (I highly doubt it).

RobertJasiek: No (unless you do not apply any ko rules). I am currently researching in identifying the ko intersections from the non-ko intersections, so one cannot be precise in general about the distinction of [k] and [t] yet.

Herman: If I understand correctly, your definition currently depends on the term force (mathematical)? So:

[Diagram]

B6 tenuki/pass

This constitutes a 5 move cycle, but since it is voluntary, it isn't [kkkkkp], correct?

Yes. --rj

Bill: Ah! Another case of sending three, returning two, n'est-ce pas? ;)

Herman: Oui! This was the first thing that came to my mind for a 5 move cycle when writing the cycle page, but it's boring because it's not forced :)

Thoravatahr: Does the one move cycle need a tag that it isn't a cycle, there is no force to commit suicide.

Herman: If it is allowed, then a player can use it to avoid passing, and can draw out the game infinitely long with the sequence: Pass, Suicide, Pass, Suicide, Pass, Suicide, etc. So rules must take it into account.

RobertJasiek: Presumably there is some freedom of definition. Either one includes it or one does not. It has already caused some nightmares for me (definitions require care) but probably I will either include or exclude it depending on which is easier or more consistent when formulating the final definitions. Even then one might alter them to suit other research better. - Yes, that a one move cycle can be a surprising means to force something is crucial indeed. Therefore so far I simply exclude it to make my life as a definition finder (a tiny bit) easier. - I was more frightened by the opponent of the one trying to force a cycle though!


RobertJasiek: In view of the [ext] recent research, the page needs an update of its contents.

Herman: In the section "Presuppositions and Basic Definitions I", the term cycle is claimed to be defined elsewhere, so presumably this research does not redefine the term cycle?

RobertJasiek: The meaning of positional / situational cycle is well known. (The parent page defines positional cycle only though.) There can be different annotations though. No, I do not mean to redefine cycle in my paper. The parent page Cycle needs a major update though because it is abused to describe some informal generalization of ko. In this respect, there are mistakes. E.g., a ko is not always defined by only one cycle - one might have to consider a set of cycles. E.g., a subtle point is that now answer-force should substitute force. My major concern is, however, that Ko expects the Cycle page to explain general ko. It does not do that well. My paper does do it. - One thing is very clear though: Ko (in general) and cycle are two different concepts. Currently Ko suggests that they were about the same. This is desinforming.


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