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scoring eyes in seki question

https://www.lifein19x19.com/viewtopic.php?t=8990

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Re: scoring eyes in seki question

Posted: Fri Feb 21, 2014 3:56 pm
by phillip1882
i would not count that as seki personally.
Click Here To Show Diagram Code
[go]$$c Unfillable Dame? \n(Japanese Rules, No prisoners, 5.5 Komi).
$$ ---------------------
$$ | . . O . . O X . X |
$$ | O O O O O O X X O |
$$ | X X X X X O O X . |
$$ | . . . . X O T X . |
$$ | . X . . X O O X X |
$$ | X . X X X X O O T |
$$ | X X O O O X X O O |
$$ | O O . . O X . X O |
$$ | . . O O O X X X O |
$$ ---------------------[/go]
if it white to play, white threatens a capture by playing either of the triangle points.
black must capture in response, leaving him with 1 fewer point.
if its black to play, he either needs to capture or pass.
either way i don't see how this could possibly be considered seki.

Re: scoring eyes in seki question

Posted: Sat Feb 22, 2014 9:32 am
by skydyr
phillip1882 wrote:i would not count that as seki personally.
Click Here To Show Diagram Code
[go]$$c Unfillable Dame? \n(Japanese Rules, No prisoners, 5.5 Komi).
$$ ---------------------
$$ | . . O . . O X . X |
$$ | O O O O O O X X O |
$$ | X X X X X O O X . |
$$ | . . . . X O T X . |
$$ | . X . . X O O X X |
$$ | X . X X X X O O T |
$$ | X X O O O X X O O |
$$ | O O . . O X . X O |
$$ | . . O O O X X X O |
$$ ---------------------[/go]
if it white to play, white threatens a capture by playing either of the triangle points.
black must capture in response, leaving him with 1 fewer point.
if its black to play, he either needs to capture or pass.
either way i don't see how this could possibly be considered seki.
Yeah, that diagram is "Black owes a move" not seki.

Re: scoring eyes in seki question

Posted: Mon Feb 24, 2014 9:39 am
by Mef
skydyr wrote:
phillip1882 wrote:i would not count that as seki personally.
Click Here To Show Diagram Code
[go]$$c Unfillable Dame? \n(Japanese Rules, No prisoners, 5.5 Komi).
$$ ---------------------
$$ | . . O . . O X . X |
$$ | O O O O O O X X O |
$$ | X X X X X O O X . |
$$ | . . . . X O T X . |
$$ | . X . . X O O X X |
$$ | X . X X X X O O T |
$$ | X X O O O X X O O |
$$ | O O . . O X . X O |
$$ | . . O O O X X X O |
$$ ---------------------[/go]
if it white to play, white threatens a capture by playing either of the triangle points.
black must capture in response, leaving him with 1 fewer point.
if its black to play, he either needs to capture or pass.
either way i don't see how this could possibly be considered seki.
Yeah, that diagram is "Black owes a move" not seki.
Except that black doesn't owe a move! If white fills the two triangled points, then J8 is dead as it stands and white loses.

Re: scoring eyes in seki question

Posted: Mon Feb 24, 2014 10:56 am
by mitsun
Why does it matter who fills the dame? If the dame are left unfilled, one side will win. Therefore the other side will fill the dame. After that a ko may be played, and the result may depend on the rule set (in particular whether passing costs a point). But the position will not end up seki under any rule set.

Re: scoring eyes in seki question

Posted: Mon Feb 24, 2014 11:39 am
by Mef
mitsun wrote:Why does it matter who fills the dame? If the dame are left unfilled, one side will win. Therefore the other side will fill the dame. After that a ko may be played, and the result may depend on the rule set (in particular whether passing costs a point). But the position will not end up seki under any rule set.

If black fills the dame, the size of the ko is larger and black does not have a big enough threat to win it. Black loses by a larger margin if he fills the dame. If white fills the dame, black has a ko threat and can win the ko (also winning the game). This means that either player filing the dame will cause themselves to lose points...they thus remain unplayed. Under Japanese 1989 rules living stones with dame are seki, and score no points. This is a seki under J89 rules.

Re: scoring eyes in seki question

Posted: Mon Feb 24, 2014 3:22 pm
by mitsun
Ah, finally I get it. W is content to let the position remain seki, since the "no points in seki" rule then gives him a win. But B does not want to fill the dame to prevent seki, since those stones would end up as extra captures for W if he wins the eventual ko.

Re: scoring eyes in seki question

Posted: Mon Mar 03, 2014 12:25 pm
by phillip1882
but...
black can capture the 1 white stone first and make it not seki!
white may win, but if so then white will definitely win with it being seki.
if j89 rules really state that, then its to blacks advantage to capture.

Re: scoring eyes in seki question

Posted: Tue Mar 04, 2014 1:05 am
by Mef
phillip1882 wrote:but...
black can capture the 1 white stone first and make it not seki!
white may win, but if so then white will definitely win with it being seki.
if j89 rules really state that, then its to blacks advantage to capture.
If black plays an extra move to capture the white stone, he will be playing in his own territory and will lose a point.

Re: scoring eyes in seki question

Posted: Sat Mar 15, 2014 5:56 am
by phillip1882
but he would have to play it anyway, if white filled the dame, and capturing the stone and losing 1 point is better than letting the postion be seki and losing more.

Re: scoring eyes in seki question

Posted: Wed Mar 19, 2014 12:53 pm
by Mef
phillip1882 wrote:but he would have to play it anyway, if white filled the dame, and capturing the stone and losing 1 point is better than letting the postion be seki and losing more.

No, if white fills the dame then the white stone is dead without black making a move to capture. Black wins the game.

Re: scoring eyes in seki question

Posted: Sat Apr 19, 2014 1:15 pm
by phillip1882
no, if white fills the dame he can fight the ko.

Re: scoring eyes in seki question

Posted: Sat Apr 19, 2014 4:13 pm
by Mef
phillip1882 wrote:no, if white fills the dame he can fight the ko.
Click Here To Show Diagram Code
[go]$$Wc :b2:=pass, :w7: @ 1, :b10: @4, :w11:=pass, :b12: @ a
$$ ---------------------
$$ | . . O . . O X 1 4 |
$$ | O O O O O O X X O |
$$ | X X X X X O O X 3 |
$$ | 6 . . . X O O X a |
$$ | 5 X . . X O O X X |
$$ | X . X X X X O O O |
$$ | X X O O O X X O O |
$$ | O O 8 . O X . X O |
$$ | . 9 O O O X X X O |
$$ ---------------------[/go]
In order to start the ko white must find the first threat and make an extra play in black's area (Move 3 in the diagram). On this board both white and black have 1 threat. That means that black will win the ko and get an extra point from white's additional play in his territory. So he can now capture to settle the ko and win the game.

Once white has filled the dame white has lost the game.

Re: scoring eyes in seki question

Posted: Thu Jun 05, 2014 12:55 pm
by phillip1882
okay if the ko is a bad deal for white, then black can fill the dame with no harm done.
i still fail to see how this is seki.
edit: okay i think i understand now. if black fills the dame, the group is now large enough that killing it is worth more to white than saving his corner.
Click Here To Show Diagram Code
[go]$$c Unfillable Dame? \n(Japanese Rules, No prisoners, 5.5 Komi).
$$ ---------------------
$$ | . . O . . O X 2 . |
$$ | O O O O O O X X O |
$$ | X X X X X O O X 4 |
$$ | . . . . X O X X . |
$$ | . X . . X O O X X |
$$ | X . X X X X O O 1 |
$$ | X X O O O X X O O |
$$ | O O 5 . O X . X O |
$$ | . 3 O O O X X X O |
$$ ---------------------[/go]

Re: scoring eyes in seki question

Posted: Mon Feb 16, 2015 12:26 pm
by Pio2001
xed_over wrote:so white's two points count and black's one doesn't?
Click Here To Show Diagram Code
[go]$$Wc
$$ -------------------------+
$$ . . X . . . X O O C O . |
$$ . X . X O . X O C O X X |
$$ . . X X . . X O O X X C |
$$ . . , X X . X O O X X X |
$$ . . . O X X O O O X O O |
$$ . . . O O O X X X O O . |
$$ . . . . . . O X O . . O |
$$ . . . . . . O X O O O . |
$$ . . . . . . O X X O . . |
$$ . . , . . O . O X O . . |
$$ . . . . . O . O X X O . |
$$ . . . . . . X X X X O . |
$$ . . . . . . . . . . . . |[/go]
Is that the correct way to score this using traditional Japanese rules?
Hi,
Yes, as stated above, under traditional japanese rules, this is a seki, and there are no points in the marked intersections.

But, as Robert pointed out in his article, things may be different under modern japanese rules (1989). As I understand the rules, white has one point in Q18, but R19 and T17 are not territory and are worth zero.

Explanation : none of the 4 involved chains is capturable. Thus, according to article 7, they are alive.
According to article 8, the circled intersections are eyes, and T19 is a dame.

But the trick is that according to the new definition of seki, only the white stone S19, and the black chain in T18, are in seki, because they are the only chains that have a dame. The R18 and Q19 chains are not in contact with the dame, thus they are not in seki.

Since Q18 is completely surrounded by living stones that are not in seki, it is a territory.

Re: scoring eyes in seki question

Posted: Mon Feb 16, 2015 7:26 pm
by Bill Spight
Pio2001 wrote:
xed_over wrote:so white's two points count and black's one doesn't?
Click Here To Show Diagram Code
[go]$$Wc
$$ -------------------------+
$$ . . X . . . X O O . O a |
$$ . X . X O . X O . O X X |
$$ . . X X . . X O O X X C |
$$ . . , X X . X O O X X X |
$$ . . . O X X O O O X O O |
$$ . . . O O O X X X O O . |
$$ . . . . . . O X O . . O |
$$ . . . . . . O X O O O . |
$$ . . . . . . O X X O . . |
$$ . . , . . O . O X O . . |
$$ . . . . . O . O X X O . |
$$ . . . . . . X X X X O . |
$$ . . . . . . . . . . . . |[/go]
Is that the correct way to score this using traditional Japanese rules?
Hi,
Yes, as stated above, under traditional japanese rules, this is a seki, and there are no points in the marked intersections.

But, as Robert pointed out in his article, things may be different under modern japanese rules (1989). As I understand the rules, white has one point in Q18, but R19 and T17 are not territory and are worth zero.

Explanation : none of the 4 involved chains is capturable. Thus, according to article 7, they are alive.
According to article 8, the circled intersections are eyes, and T19 is a dame.

But the trick is that according to the new definition of seki, only the white stone S19, and the black chain in T18, are in seki, because they are the only chains that have a dame. The R18 and Q19 chains are not in contact with the dame, thus they are not in seki.

Since Q18 is completely surrounded by living stones that are not in seki, it is a territory.
Well, the J89 rules have been around for a long time, and it is clear that there are no points in seki, nor was there an intent to change that from the J49 rules. So somehow all of the White stones in the corner own the dame at "a". In my revision of the J89 rules I write, "All stones that surround the same eye points belong to the same group. A group is called a seki group if it adjacent to a neutral point, or if one or more of its stones is in atari." That is clearer than the J89 text, I think. See http://senseis.xmp.net/?SpightJapaneseStyleRules :)
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