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Superko Anomalies
Keywords: Rules
Bill: As, I believe, John Fairbairn pointed out, the Law of Unintended Consequences seems to affect go rules. Rules intended to take care of certain rare, anomalous or undesirable situations may give rise to different rare, anomalous or undesirable situations. Ikeda? made a similar point. The superko rule, in different versions, while allowing certain multiple ko situations and repetitious positions such as Eternal Life to be played out rather than continuing indefinitely, has also given rise to certain rare anomalies or undesirable situations, at least on paper. RobertJasiek: Unexpected behaviour, which you call anomalies, can occur for various rules. E.g., historically one of the unexpected behaviours of the basic-ko rule has been that long cycles can occur... Here are more BasicKoAnomalies. Example 1One such reportedly motivated Ing to change his rules to distinguish between fighting and disturbing kos. Andrew Grant: Another reason for disliking superko is that it can lead to some odd life and death decisions. For instance, in the diagram, White is alive: if Black plays a, White replies at b.
But add another such "live" group and the status changes:
White cannot now play
You can accept this as just a feature of superko, but it's very odd that if you have one of these groups it's alive but having two of them makes it killable. I believe that it was considerations like this that led Ing to introduce his distinction between fighting ko and disturbing ko.
RobertJasiek: Odd life and death outcomes are not a pecularity of superko but also of every other ko ruleset. E.g., Japanese ko rules lead to strange outcomes.
Bill: The Method of Multiples, as applied to this superko, shows that it, like a regular ko, has a cycle of 3, where 4 of them leave one double ko death with the rest miai, as does 7 of them, 10 of them, etc. That suggests that the double ko death is the odd man out. ;-)
OC, the method of multiples assumes something like superko to keep indefinite repetition from preventing assessment of positions with many multiples. So there is some circularity, if you are trying to do more than show the implications of the superko rule. But it does show that the rule does not "bring a dead group to life." Anonymous: Another anomaly: Under Superko, double ko seki can't serve as ko threat:
Now Black 6 would recreate the starting position and is forbidden with Superko. The ko on the left then is lost for White, but the double ko seki is presumably bigger.
"No player may play a stone so that it recreates a position of the board which that player has already created before." With this rule, your first example, with 1 shape makes a normal ko and lives only cause there are no ko threats. In the second example, it does apply that white cannot play 8 without a ko threat first (so that 1-7 sequence becomes the 'play' a player does between each ko threat), if broken, it'll lead to that 1 group lives and 1 dies, I do not see the problem with this, it dies because you do not have any ko threats, making a copy of the shape creates ko threats! If we wouldn't consider super ko rules, it'd still lead to the first group living but in teh second case, they'd go on for infinity (or alike). Does it make more sense when compared to the first example? This is a copy of the living page "Superko Anomalies" at Sensei's Library. ![]() |