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Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 10:55 am
by Kirby
Thanks for the responses, folks. I think that I've got the nuance. I'm trying to think of another shape with the same properties as bent-4, but that is not bent-4, but I'm having difficulty doing so.
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 10:57 am
by yoyoma
Kirby wrote:So maybe this can be generalized to say that, when we are analyzing shapes under Japanese rules, we must assume that neither side has any ko threats?
http://www.cs.cmu.edu/~wjh/go/rules/Japanese.htmlArticle 7. Life and death
1. Stones are said to be "alive" if they cannot be captured by the opponent, or if capturing them would enable a new stone to be played that the opponent could not capture. Stones which are not alive are said to be "dead."
2. In the confirmation of life and death after the game stops in Article 9, recapturing in the same ko is prohibited. A player whose stone has been captured in a ko may, however, capture in that ko again after passing once for that particular ko capture.
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 11:18 am
by Kirby
yoyoma wrote:Kirby wrote:So maybe this can be generalized to say that, when we are analyzing shapes under Japanese rules, we must assume that neither side has any ko threats?
http://www.cs.cmu.edu/~wjh/go/rules/Japanese.htmlArticle 7. Life and death
1. Stones are said to be "alive" if they cannot be captured by the opponent, or if capturing them would enable a new stone to be played that the opponent could not capture. Stones which are not alive are said to be "dead."
2. In the confirmation of life and death after the game stops in Article 9, recapturing in the same ko is prohibited. A player whose stone has been captured in a ko may, however, capture in that ko again after passing once for that particular ko capture.
Cool. Thank you.
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 1:26 pm
by SpongeBob
Wow - one can become KGS 1d without understanding bent 4 - I am impressed.
(No offence intended, Toge, I wish I will reach 1d myself one day ...)
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 4:30 pm
by Toge
SpongeBob wrote:Wow - one can become KGS 1d without understanding bent 4 - I am impressed.
(No offence intended, Toge, I wish I will reach 1d myself one day ...)
- Well this virtual playing thing was completely new to me. I've never played Go over the board. I've also had just intuitive understanding what constitutes living group. I think Kirby's example is excellent.
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 5:14 pm
by hyperpape
Don't feel too left out. I didn't hear about virtual play from any time I played face to face games. It came from sensei's library and rules discussions on these boards.
Re: Bent four in corner and Japanese rules.
Posted: Tue Jun 21, 2011 9:16 pm
by jts
Toge wrote:SpongeBob wrote:Wow - one can become KGS 1d without understanding bent 4 - I am impressed.
(No offence intended, Toge, I wish I will reach 1d myself one day ...)
- Well this virtual playing thing was completely new to me. I've never played Go over the board. I've also had just intuitive understanding what constitutes living group. I think Kirby's example is excellent.
Out of curiousity: do you think you've ever marked a dead group as living because you didn't understand this wrinkle in the rules?
Re: Bent four in corner and Japanese rules.
Posted: Wed Jun 22, 2011 2:40 am
by Toge
jts wrote:Out of curiousity: do you think you've ever marked a dead group as living because you didn't understand this wrinkle in the rules?
- Possibly when I was a beginner. I can't remember. I've known that bent four is dead shape, but not the reasons why. Usually it would turn into ko.
Re: Bent four in corner and Japanese rules.
Posted: Wed Jun 22, 2011 5:11 am
by RobertJasiek
To answer the OP question, bent-4 is dead under Japanese rules because,
1) if the question is for historical reasons, the standard answer is that the rules authors among the Japanese professionals overlooked both unremovable threats and bent-4-seki shapes,
2) if Japanese rules are pre-1989 style rules and the question is for the rules application, the rules say so in a precedent,
3) if Japanese rules are the 1989 rules and the question is for the rules application before a game stop, application of rules is irrelevant,
4) if Japanese rules are the 1989 rules and the question is for the rules application after a game stop, the pass for ko rule (regardless of whether applied in all its ambiguity or in the unambiguous context of J2003 interpretation) creates the effect that bent-4 is dead (i.e. the stones around the corner nakade are dead),
5) if certain modern written forms of verbal Japanese rules are used and the question is for the rules application before a game stop, application of rules is irrelevant,
6) if certain modern written forms of verbal Japanese rules are used and the question is for the rules application after a game stop, the basic ko rule creates the effect that bent-4 is dead (i.e. the stones around the corner nakade are dead).
Re: Bent four in corner and Japanese rules.
Posted: Fri Jun 24, 2011 4:55 am
by Mef
Kirby wrote:In the case of the shape I brought up, black cannot do that because he will repeat the board position, maybe:
$$Bm1
$$ ----------------
$$ | X X 2 X O X .
$$ | 1 O X . O X .
$$ | O O O O O X .
$$ | X X X X X . .
$$ | . . . . . . .
$$ | . . . . . . .
- Click Here To Show Diagram Code
[go]$$Bm1
$$ ----------------
$$ | X X 2 X O X .
$$ | 1 O X . O X .
$$ | O O O O O X .
$$ | X X X X X . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]
$$Bm1
$$ ----------------
$$ | 5 3 . X O X .
$$ | . O X . O X .
$$ | O O O O O X .
$$ | X X X X X . .
$$ | . . . . . . .
$$ | . . . . . . .
- Click Here To Show Diagram Code
[go]$$Bm1
$$ ----------------
$$ | 5 3 . X O X .
$$ | . O X . O X .
$$ | O O O O O X .
$$ | X X X X X . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]
Is that why it's different? Black can still start the ko, though, so there must be some nuance in the rationale here.
Japanese rules don't have superko, so B is free to repeat this position as much as he wants (though he loses 2 points every time he does from the capture difference). Eventually if B repeats it enough times, white just gives up the group (because he has enough points to win). As mentioned B can't win the ko (because white captures first, and no threats other than pass are allowed).
Kirby wrote:Thanks for the responses, folks. I think that I've got the nuance. I'm trying to think of another shape with the same properties as bent-4, but that is not bent-4, but I'm having difficulty doing so.
Not quite the same thing, but another position you may find interesting is
three points without capture
Re: Bent four in corner and Japanese rules.
Posted: Fri Jun 24, 2011 6:55 am
by Kirby
Thanks, that is interesting.