Hello,
(My apologies, if this is not the correct place/way to ask this question.)
How are triple kos handled on OGS? We have reached an infinite loop in Ladder Challenge: Dyonn(#15) vs Seehuhn(#14) and I’m not sure what should happen now.
Many thanks,
Jochen
OGS doesn’t have built-in support to handle triple ko situations, but if a Japanese rules game gets stuck in a cycle that neither player is willing to break from, the moderators can manually declare the game as an annulled tie. I’ll take a look at it.
Ok, so this is an interesting situation. I see that you’ve already found a highly relevant forum thread:
So, if both players insist on continuing the cycle and agree to a “no result”, we can declare this game as a “no result”.
However, as noted in that thread, that’s not the only way to proceed, and possibly suboptimal. It’s a tricky situation to handle, as I’m trying to find a middle ground between being helpful and not offering too much external advice.
We are both happy to go with “no result”. Can you arrange this for us?
I’m looking forward to your comments. Is “passing for a particular ko” a real thing?
Ok, since both players have clearly indicated their intention to not break the cycle and want a “no result”, I have ended the game as such (through the workaround of declaring an annulled tie, since we don’t have official support to specifically indicate a “no result”).
Now that this game is over, I’d like to comment on this very interesting situation.
The core shape, if considered in isolation (while assuming that the outside stones, particularly the Black chain at C5, are all alive), is an example of self-contained moonshine life, similar to the type discussed in the other thread linked above (Interesting double/potential triple ko(/seki ?)!).
Had the Black chain at C5 been unquestionably alive (e.g., imagine if there were two more stones at A5 and B4), then this moonshine life position would have resolved with White (the D4 chain) being considered dead (during the life and death determination phase). Note that while Black cannot capture White during normal alternating play (since White can just cycle the position), there are special ko rules during the life and death determination phase that cause White to be considered to be dead, and Black would be able safely tenuki (in this hypothetical situation of imagining that the C5 chain was safe).
However, what makes this game different is that the external stones were not all safe. In particular, the Black chain at C5 is dead and can be easily captured in continued play, which would cause the contained moonshine life to completely collapse. Had Black not forced the cycle, White could eventually capture the C5 chain and save their D4 stones, and also kill Black’s G4 chain, which would to a large win by White. Thus, Black is compelled to attempt to capture White’s D4 chain and potentially cycle the game.
On the other hand, it is also an interesting question to consider whether White should accept the cycle (and “no result”) or perhaps consider abandoning it to let Black settle the moonshine life through capture of the D4 stones, while saving their C5 chain. This all depends, of course, on how the game might play out, which is not entirely clear to me, as it would require some careful endgame analysis. I haven’t analyzed that carefully, but I think the result might be close, and Black even shared a variation in the post-game chat of a potential play out where White may win. If White strongly believed that abandoning the cycle would have led to a loss, then of course it is sensible for White to persist with the cycle and accept the “no result”. However, I’m not sure if that was the strategically optimal choice.
In general, this sort of situation requires not only a judgement of how one believes the game might play out, but also a consideration of one’s appetite for risk, in light of the potential uncertainty in one’s judgement of the position. In general, White could be faced with such a situation where the remaining end game is very complex, but close, and they can only roughly estimate their chances of winning. For example, White may be faced with the following choice:
It becomes a rather personal choice as to how large that estimated X% must be in order to go with that second path.
Overall, this situation is quite complex, and I’ll add the disclaimer that I may have misunderstood and incorrectly analyzed some things. It gave the initial appearances of a triple ko (due to three cycling kos), but then appeared to be a moonshine life (due to specific shape of one-eye vs none), and then finally back to what seems to be triple ko (due to the lack of stability in the surrounding stones). Hence, I wanted to be careful that both players were clearly acknowledging their persistence in cycling and acceptance of the no result, especially in light of the forum thread about moonshine life having been mentioned.
Yes, in the sense that formal application of the Japanese rules have technicalities that need to be considered to properly resolve life and death determinations involving ko. I discuss this in a bit more detail in this forums post (Odd Cases 🤔 in the Japanese Rules - #8 by yebellz), where I use the bent-four-in-the-corner as an example.
Thanks a lot for these detailed comments. I’ll take a bit of time over the weekend to think this through.
Until then, a simple question: was this at the end actually a “triple ko”, or would this require for all three kos to be between the same two groups?
In general, the kos don’t have to all belong to the same two groups. It just needs to be a cycle involving three kos that neither player is willing to break from. Here is an example given on Sensei’s Library:
However, a related question is whether or not a game should end with a “no result” via triple ko, or if it is strategically better for a player abandon the cycle in order to obtain a better result. In cases where it would have been better for one player to abandon the cycle, some might call that as not a “real” triple ko, as it was strategically suboptimal.
triple ko can lead go to a draw.
there is a real triple ko that make a game draw, and a fake triple ko that is not a draw.
also there is a quadruple ko which will lead the game to a draw
(These are all in Japanese rules.)
