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| do I have to capture that group? http://lifein19x19.com/viewtopic.php?f=45&t=5913 |
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| Author: | entropi [ Thu May 03, 2012 12:58 am ] |
| Post subject: | do I have to capture that group? |
An unfinished game. I play white. I am puzzled whether I have to capture j12 stones or not. If the liberties at e14 and e11 are filled, it can become a fake seki between white g13 and black-h13 groups. The seki would be fake because the top black group (h17) is dead anyway. But the question is, whether my opponent can argue (if yes according to which rule set?) that I need to capture either one of the g16 or h17 groups before I can claim g16 dead. My guess is that I don't need to capture it because I can easily prove in "dispute mode" that both h13 and g16 black groups are dead. But I am not sure about the rule sets. The difference would be 5 points (if it comes to the fake seki) or just 1 point (if I have to prevent the fake seki). It would probably not change the result of the game but anyway it would be interesting to know. PS: In case you see any tesuji, anywhere on the board for or against any one of the players, please don't indicate anything, because this is an unfinished game! Thank you The fake seki I was mentioning: |
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| Author: | EdLee [ Thu May 03, 2012 1:22 am ] |
| Post subject: | |
No. entropi wrote: it can become a fake seki Look more closely. It's eye vs. no eye. B cannot get seki there -- W kills J12 first. Play it out.(Even if you pass twice and let B fill in both H10 and H12 and get a fake seki in the middle, you still don't need to capture it, because as you said, H17 is dead, and so is J12.) |
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| Author: | HermanHiddema [ Thu May 03, 2012 1:25 am ] |
| Post subject: | Re: do I have to capture that group? |
You do not need to capture either group under all major rule sets. (Under Japanese style rules, you can indeed prove they are dead in "dispute mode".) |
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| Author: | entropi [ Thu May 03, 2012 1:27 am ] |
| Post subject: | Re: |
EdLee wrote: No. entropi wrote: it can become a fake seki Look more closely. It's eye vs. no eye. B cannot get seki there -- W kills J12 first. Play it out.EdLee, of course white can kill it first. But white needs to put one move inside his own territory for killing it while black plays dame points. The question is whether I have to prevent this fake seki (as you mention) or whether I can claim the black group dead straight away. |
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| Author: | EdLee [ Thu May 03, 2012 1:29 am ] |
| Post subject: | |
entropi wrote: whether I can claim the black group dead straight away. You can claim the B group dead straight away without adding any more moves.
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| Author: | RobertJasiek [ Thu May 03, 2012 2:51 am ] |
| Post subject: | Re: do I have to capture that group? |
entropi wrote: All rulesets: The group is captured. The question is whether and how you need to remove it. Area scoring rulesets, players' agreement: Count. Area scoring rulesets, players' disagreement: Play it out by continuing alternation, i.e., remove all opposing strings you can remove. All Japanese-style territory scoring rulesets, players' agreement: Count. All Japanese-style territory scoring rulesets, players' disagreement: The exact handling depends on the used ruleset. Those rulesets have in common though that removal is performed hypothetically. Example of a Japanese-style territory scoring ruleset: Japanese 1989 Rules: Read http://home.snafu.de/jasiek/j1989c.html http://home.snafu.de/jasiek/j2003.html http://home.snafu.de/jasiek/j2003com.html http://home.snafu.de/jasiek/j2003inf.html Afterwards tell us what is still unclear to you, because it is no fun to spend 2 ~ 5 hours on explaining a step-by-step application. You need to study different positions: the current unfinished position; the position after dame filling and game stopping passes. |
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| Author: | entropi [ Thu May 03, 2012 3:55 am ] |
| Post subject: | Re: do I have to capture that group? |
Thank you for all the replies. They are in line what I would have guessed anyway, but neither my opponent nor myself were sure so I just wanted to ask you guys. |
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| Author: | Charlie [ Fri May 18, 2012 1:48 am ] |
| Post subject: | Re: do I have to capture that group? |
I think black would be silly to let the game end before filling up the outside liberties (which cost him nothing, assuming white is passing already) and forcing white to play either H12 or H10, which costs white 1 point. As soon as white passes once, white can't do anything to prevent this - all black has to do is not pass until H10 or H12 are played. |
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| Author: | Cassandra [ Fri May 18, 2012 2:32 am ] |
| Post subject: | Re: do I have to capture that group? |
Charlie wrote: I think black would be silly to let the game end before filling up the outside liberties (which cost him nothing, assuming white is passing already) and forcing white to play either H12 or H10, which costs white 1 point. There is no need for White to play inside, because Black cannot put her group in Atari, due to her eye at E17. |
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| Author: | Charlie [ Fri May 18, 2012 3:54 am ] |
| Post subject: | Re: do I have to capture that group? |
If white does not play into his or her territory, black can play as follows before ending the game: To me, this is Seki because white cannot capture black without playing self-atari and black can't capture white without self-atari. I read Robert Jasiek's summary of the 1989 rules and 2003 rules and here are some quotes: Quote: A player's final-string is uncapturable if the opponent cannot force capture of its stones. Quote: A player can force something if there is at least one hypothetical-strategy of his so that each compatible hypothetical-sequence fulfils that something. Quote: For each hypothetical-strategy of the opponent, the player can find several answers but the player must find AT LEAST ONE answer to succeed. If we consider the black stones, the opponent is white and any feasible hypothetical strategy of white's that aims to capture the black string will involve self-atari. Blacks hypothetical answer will be to capture white. That counts as at least one, in my mind, and is sufficient to prove that black is uncapturable. Similarly, white is uncapturable. Howerver, in truth, that is all irrelevant because: Quote: In the final-position, an intersection of a black-eye-string / white-eye-string is a black-eye-point / white-eye-point if the black-eye-string / white-eye-string is adjacent and only adjacent to intersections with stones of one or more than one alive black-strings / white-strings. In the final-position, an eye-point is either a black-eye-point or a white-eye-point. In the final-position, a dame is an empty intersection that is not an eye-point. In the final-position, a black-region / white-region is an intersection with a stone of an alive black-string / white-string and, recursively, any adjacent intersection that has a stone of an alive black-string / white-string or is a black-eye-point / white-eye-point. In the final-position, a black-region / white-region is in-seki if at least one of its intersections is adjacent to a dame. So H10 is clearly "dame" and the result is clearly "seki". If black were to play 1 and 3 and not play 5 and the final position looked as follows, things would be different. At this point, the white stones would be uncapturable according to my former argument but black would be dead because, when considering whether black's groups are uncapturable, white gets to play the first move in the hypothetical sequence and white could play either H10 or H12. Assuming that black is not an idiot, after 3, white should expect black 5 as in my first diagram because black would prefer the seki to outright death. To prevent black 5, surely white should play H10 or H12, sacrificing a point? There is something, here, that I just don't understand. |
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| Author: | HermanHiddema [ Fri May 18, 2012 4:02 am ] |
| Post subject: | Re: do I have to capture that group? |
You're missing that the black group at the top is dead, so the seki is what is called a temporary seki, and hence it is dead at the end of the game. |
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| Author: | Charlie [ Fri May 18, 2012 4:07 am ] |
| Post subject: | Re: do I have to capture that group? |
Aha. That's it. Then _this_ would be seki? |
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| Author: | HermanHiddema [ Fri May 18, 2012 4:19 am ] |
| Post subject: | Re: do I have to capture that group? |
Yes |
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