Life in 19x19. Go, Weiqi, Baduk... Thats the life.
https://lifein19x19.com/
is black allowed to capture at a or does he need to play at b?Matti wrote: If white claims komaster and plays at
does not take or fill the ko. If White claims komaster status for a, White must fill it. Then Black can capture White, so White's claim fails.Assuming this is the whole board. White as komaster must fill the ko, then Black will take the other ko and capture White. Black as komaster must take and then fill the ko. Since White cannot atari Black, White is a goner.moha wrote:It's not clear to me what are the exact consequences of a "komaster claim" regarding move legality.
(mandatory moves? immediate ko resolution? is it enough to resolve the ko some time after taking it?)
But he cannot fill immediately (if W resists). Is it enough if he fills a few moves later? Or B gets two moves in a row? What are the exact conditions?Bill Spight wrote:Black as komaster must take and then fill the ko.
Ah, OK. Nice point.moha wrote:But he cannot fill immediately (if W resists). Is it enough if he fills a few moves later? Or B gets two moves in a row? What are the exact conditions?Bill Spight wrote:Black as komaster must take and then fill the ko.
is allowed. It prevents Black from winning the ko, since Black is captured if she does.
is allowed, because is not an arbitrary threat. Then 
cannot be prevented. threatens to save White. However, stops play because Black has successfully resolved the ko, thus verifying her komaster claim. For subsequent play, which is necessary to show that White dies, we cancel and revert to the original diagram. I think that this answers the inefficiency objection. This is an idea I have had in the back of my mind for some time, but I had not written anything down yet. I decided to bring it up in response to lightvector's topic about his version of the Japanese rules. It is based upon Berlekamp's original komaster rule, where the komaster gets two moves in a row (unless only one is needed to win the ko). I have adapted it for play at temperature -1 and for multiple kos, and I allow each player to attempt to claim komaster status.moha wrote:Ok, so resolving the ko can wait. But I still don't see all conditions of this approach - have you written them somewhere?
Since White is claiming komaster status for the top ko, Black cannot take it back. And by ordinary ko rules Black cannot take the double ko back, either. That allows White's komaster claim to succeed. Then there is still the double ko to resolve, but it is fairly obvious that Black is dead.For example, the last diagram of the post you refer to ("white komaster, variation") seems unclear. If W only aim to resolve the ko, the previous diagram seems better for him. If not, I don't see how he could capture (or achieve anything) in the last diagram if B insist on the cycle. What rules are in place there?
at 
Black has no local play. White can then win the ko by capturing the Black stones, assuring life. If Black plays elsewhere White ignores the play, since he can make a successful claim. Presumably White could make a successful claim by filling the ko with , but this way there is no question.Ok, this is what I missed earlier.Bill Spight wrote:Since White is claiming komaster status for the top ko, Black cannot take it back.
Initially, neither player can claim komaster status of either ko on the right. For example,moha wrote:Ok, this is what I missed earlier.Bill Spight wrote:Since White is claiming komaster status for the top ko, Black cannot take it back.
is allowed as a response to 
. Then must resolve the ko, and 
captures. I guess your point is that, since Black can reply to instead of filling, that would lift the ban on taking back, and Black can capture White in the corner. at 
to remain in effect during the process. So I guess we should keep all ko bans in effect, to keep other ko fights from interfering with the process. at 
unless it allows Black to capture , thus denying White's komaster claim. If it does so, then we will allow to reply at a, which does save . captures , so Black's claim fails. Maybe Black can succeed if she becomes komaster for the ko. and safely win the ko. But White has a reply to prevent the capture with . at is allowed in order to refute Black's claim. fills the ko, but not safely, as captures . at takes the ko. 
is allowed to prevent the capture with . is allowed because filling the ko at is unsafe, and defends the komaster claim by making it safe to win the ko. Finally, wins the ko. can safely win the ko. What about White? at , but not safely, as captures . does not resolve the ko. The second play in a row must resolve the ko. (At higher temperatures before the end of play it might be allowed, however.) and win the ko. White is dead. is allowed to refute Black claim. is allowed to make it safe to resolve the ko. wins the ko. White is dead.In that last example I wondered about the komaster status of left kos (cannot W claim, fill and avoid capture?). I'm still not sure if I understand everything about this approach yet.Bill Spight wrote:I guess your point is that, since Black can reply to