121.45.221.107: Status in rules (2018-08-25 04:39) [#11162]

Is this definitely seki in both Japanese and Chinese rules / professional play?

What about super-ko?

Thinking through it myself.. at no point will any player fill a ko (lest self-atari of entire group). If opponent takes a ko (and no threats remain elsewhere) must immediately take other ko or die. So who runs afoul of superko? After last external move or threat-answer played, say it is B turn:

(1) B takes ko-1 (atari W) (2) W takes ko-2. (Maybe B passes for ko-2, and W passes for ko-1.) (3) B then retakes ko-2 (atari W) (4) W retakes ko-1, recreating the initial position.

Assuming positional superko (which I assume is the variant in both current rulesets), B's retaking of ko-2 (3) voids the game (or is maybe illegal in Chinese rules). But then, voiding the game might be desirable if B is otherwise losing.

After (2), B definitely had no alternative than to pass, but maybe W can immediately (3b) retake ko-1 (atari B). (4b) B retake ko-2, recreating the initial position (except with W to play next).

So B can force no-result. In pro games, can losing player attempt to convert double-ko seki to no-result?

BTW, are the rules clear about whether passing is a valid basic ko threat, and does super-ko rule apply in the virtual play phase (of Japanese scoring)?