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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #81 Posted: Tue Sep 14, 2021 11:14 am 
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Japanese rules judge L/D globally, with global enable (and with modified ko rules). No local view was ever mentioned in this case (that would be Korean rules btw).

With your rules and your analysis, B left cannot be captured without enabling new alive B stones at the right - stones that couldn't have been played without the capture attempt of the left.

Quote:
And I do not think that it is so very surprising that capturing something would enable you to occupy points that you were not able to occupy before.

Not you, your opponent. :D

Capturing his dead stones never enable HIM to play a new uncapturable stone that he couldn't have played originally, without being captured.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #82 Posted: Tue Sep 14, 2021 12:46 pm 
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Cassandra wrote:
What is the reason that you do not like the result at all?

Would you have wanted anything else but "Black at the left is dead; at the right, there is a double-ko seki"? If so, what?

Your answers?

I can understand that you absolutely did not expect the self-atari in the double-ko, which ruined your intended counter-example.
However, this is no reason to continue to talk around the bush, which includes nothing more than your understanding of what should not work in the sense of your supposed counter-example, but which failed.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #83 Posted: Tue Sep 14, 2021 1:25 pm 
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I cannot even make sense of your questions now. Both of YOUR analysis lines ended up W losing the right in exchange for the left (enabling new B uncapturable stones). Black on the left is alive in your rules. It doesn't matter if I like this or not.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #84 Posted: Tue Sep 14, 2021 7:03 pm 
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jann wrote:
I cannot even make sense of your questions now.

I don't think my questions were so terribly misleading.


Next attempt:

:w1: What was the intended result of your alleged counter-example?
:b1: Which status would YOU have assigned to the Black group on the left?
:b2: What status do YOU think the groups in the partial position on the right should have?


---------------------------

By the way: I have already understood that you were shocked by White's self-atari in the double-ko. And also that you assess your interpretation of "enable" to be the correct one.
However, this all will not hinder you from telling us the result of YOUR analysis of the above mentioned L&D statuses.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #85 Posted: Thu Sep 16, 2021 7:24 am 
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jann wrote:
Gérard TAILLE wrote:
jann wrote:
This is a longstanding question in J89 which has two possible answers:
  1. Maybe passing for each ko is only required once for each player (see here)
  2. Or the problem was overlooked by J89 authors, and will be fixed in the future (with some hack like requiring a normal pass of either player before passing for a ko a second time)

1)
If you use "pass once per ko" then black can pass immediatly and wins the game because the two white marked stones are dead in the confirmation phase

2)
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------–-
$$ | 2 X X O X O . . . O X O . O . |
$$ | X O 1 O X O . . . O X X O O O |
$$ | O O X X X O . . . O X . X O X |
$$ | O X X O O O . . . O X X X X . |
$$ | . O X O . . . . . O O O O X X |
$$ | . O X O . . . . . . . . O O O |
$$ | O X X O . . . . . . . . . . . |
$$ | O O O O . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . |[/go]
without using "pass once per ko", in order to win, black must continue at least one move.
After :b1: :w2: then black passes and wins the game.

Nice position, thank you. Even if harmless here since the result is the same (B can force the reinforcement with the same play either way), this does show a case where the attacker might need to play the same ko twice in confirmation.

I like challenge and, for fun, I tried to find a position with different result.
I believe the following one works.

Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . O . O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O . |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O . |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]


Let's call J89-ko-pass the J89 rule with the ko-pass instead of the pass-for-ko
Let's call J89-pass-once-per-ko the J89 rule with the pass-once-per-ko instead of the pass-for-ko

Assume that black will win the game by 0.5 points if white adds three moves in normal play to kill the black stones in the upper right corner.

Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . O W O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O . |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O W |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]

What is the point? Assume white has added the two marked stones before stopping the game.

In J89-ko-pass the upper right black group is dead => white wins the game => in normal play black must force the NO RESULT

In J89-pass-once-per-ko black group is alive by:
Click Here To Show Diagram Code
[go]$$W :b6: pass once for ko at 3
$$ ---------------------------------------
$$ | . . . . . O W O 5 7 O O 8 3 X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X 2 X 4 X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O 1 |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O W |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]
and black cannot be killed because black managed te recreate the moonshine life loop wih three ko.
=> in normal play white must add a third move => black wins the game

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #86 Posted: Thu Sep 16, 2021 9:39 am 
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Nice position again! This example shows more than just a difference between pass-once and pass-each-time (which we knew to be possible, at least theoretically).

First, let me refer to this. The supporting theory between the two approaches/interpretations differ: pass-once tries to freeze kos in relation to the stopped position, pass-each-time alters ko play balance permamently.

Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . O W O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O . |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O W |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]

Assume white has added the two marked stones before stopping the game.

In this position, not only is black right uncapturable, he can make miai of the two kos at the two edges, so is alive/uncapturable even locally. (EDIT: after 2 W reinforcement moves this is not really true anymore since B would need to play first for that now)

This is nothing like a moonshine life where the defender uses a double ko to create a faint illusion of life - this is the inverse. It is the attacker (W) who can use the double ko to force a perpetual (unsuccessful) capture attempt (of a locally alive group) and thus a valid triple ko.

This case seems similar to J89 erroneous reinforcement examples (lightvector's and others) discussed recently, where J89 ko passes change normal play and force extra plays that are incorrect and unnecessary in normal game. Pass-once seems to work better here in retaining the balance if the stopped position. Since black is uncapturable even locally (and on miai, not on infinite threats from other double kos), seems hard to justify calling him dead.


Last edited by jann on Thu Sep 16, 2021 2:04 pm, edited 1 time in total.
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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #87 Posted: Thu Sep 16, 2021 9:55 am 
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jann wrote:
This case seems similar to J89 erroneous reinforcement examples (lightvector's and others) discussed recently, where J89 ko passes change normal play and force extra plays that are incorrect and unnecessary in normal game. Pass-once seems to work better here in retaining the balance if the stopped position. Since black is uncapturable even locally (and on miai, not on infinite threats from other double kos), seems hard to justify calling him dead.


I do not see clearly your point Jann because here it seems the contrary. In J89-ko-pass white needs to add only two moves in order to kill black and in J89-pass-once-per-ko white needs to add three moves.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #88 Posted: Thu Sep 16, 2021 10:05 am 
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I meant this example is the same as lightvector's reinforcement example, where in normal play one side is clearly alive on (creatable) miai, but J89 erroneously calls him dead (because of heavily restricted ko play).

It is pass-each-time that fails in both examples (OC, in lightvector's case pass-once wouldn't help either).

Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ | O . O . X . . O O . O
$$ | O O O X O X O O O O O
$$ | X X X O . O O . O . .
$$ | X . X O O O O O . . .
$$ | . X X . . . . . . . .
$$ | X X . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #89 Posted: Thu Sep 16, 2021 11:09 am 
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jann wrote:
Nice position again! This example shows more than just a difference between pass-once and pass-each-time (which we knew to be possible, at least theoretically).

First, let me refer to this. The supporting theory between the two approaches/interpretations differ: pass-once tries to freeze kos in relation to the stopped position, pass-each-time alters ko play balance permamently.

Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . O W O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O . |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O W |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]

Assume white has added the two marked stones before stopping the game.

In this position, not only is black right uncapturable, he can make miai of the two kos at the two edges, so is alive/uncapturable even locally.

This is nothing like a moonshine life where the defender uses a double ko to create a faint illusion of life - this is the inverse. It is the attacker (W) who can use the double ko to force a perpetual (unsuccessful) capture attempt (of a locally alive group) and thus a valid triple ko.

This case seems similar to J89 erroneous reinforcement examples (lightvector's and others) discussed recently, where J89 ko passes change normal play and force extra plays that are incorrect and unnecessary in normal game. Pass-once seems to work better here in retaining the balance if the stopped position. Since black is uncapturable even locally (and on miai, not on infinite threats from other double kos), seems hard to justify calling him dead.


You say black is uncapturable?
In normal play OC I agree.
But in confirmation phase? If you assume neither player is allowed to use the double ko as an infinite number of ko threats then black is always dead due to the independence of ko which exists in confirmation phase.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #90 Posted: Thu Sep 16, 2021 11:36 am 
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Compare your example to lightvector's. In both cases one side has a decisive play that makes miai of two local kos and creates life on double ko, thus safe in normal play.

J89 doesn't recognize such life, but this is clearly a flaw/anomaly, at least in lightvector's case (revealing this defect is the very purpose of that position). In your example pass-once may actually helped.

You can also test these examples in Korean-style rules with explit local view (Korean, LJRG, or even yours). In both examples the miai life works even locally, independent of double ko sekis.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #91 Posted: Thu Sep 16, 2021 12:50 pm 
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jann wrote:
Compare your example to lightvector's. In both cases one side has a decisive play that makes miai of two local kos and creates life on double ko, thus safe in normal play.

safe in normal play ????
lightvector's position looks like
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ | O O X . X O . . . . .
$$ | O O O X O O . . . . .
$$ | . O X X O . . . . . .
$$ | O X . X O . . . . . .
$$ | X X X X O . . . . . .
$$ | O O O O O . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]
which is a death double ko isn't it?

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #92 Posted: Thu Sep 16, 2021 1:01 pm 
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Click Here To Show Diagram Code
[go]$$B :w4: above :b1:
$$ ----------------------
$$ | O . O . X 2 3 O O . O
$$ | O O O X O X O O O O O
$$ | X X X O 1 O O . O . .
$$ | X . X O O O O O . . .
$$ | . X X . . . . . . . .
$$ | X X . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

W corner safe on double ko (just like B in your example, after starting both edge kos simultaneously).

OC if you add a remote double ko seki, life on double ko may not be favorable since it allows the opponent to go for triple ko. But J89 calls both W in lightvector's and B in your original example dead even if no double ko seki exists - which is already wrong (and differs from Korean).

Correcting myself from above posts: the miai doesn't work (at least for B uncapturability) after 2 W reinforcement moves, only earlier, since B doesn't get to go first to create it.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #93 Posted: Thu Sep 16, 2021 2:00 pm 
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[quote="jann"]OC if you add a remote double ko seki, life on double ko may not be favorable since it allows the opponent to go for triple ko. But J89 calls both W in lightvector's and B in your original example dead even if no double ko seki exists - which is already clearly wrong (and differs from Korean).

Let's try to analyse the position WITHOUT double ko seki:

Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . . . . . O O O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . O X X O |
$$ | . . . . . . . . . . . . . . . O O O O |
$$ | . . . . . . . . . . . . . . . . . O O |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


In normal play black cannot be killed, even if it is white to play.
What about confirmation phase? It seems black is always dead even in J89-pass-once-per-ko! Do you agree?
BTW, OC, in GT territory rule there are no territory because GT territory rule is based on normal play.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #94 Posted: Thu Sep 16, 2021 2:09 pm 
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Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . . . . . O O O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . O X X O |
$$ | . . . . . . . . . . . . . . . O O O O |
$$ | . . . . . . . . . . . . . . . . . O O |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


In normal play black cannot be killed, even if it is white to play.

This is what I wrote above: after 2 W reinforcements, W first seem to kill now (in normal play) by connecting once on either side. B first could create the double ko life. This position seems unsettled. (EDIT: W doesn't kill only makes unfavorable ko, see below)


Last edited by jann on Thu Sep 16, 2021 2:31 pm, edited 5 times in total.
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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #95 Posted: Thu Sep 16, 2021 2:18 pm 
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jann wrote:
Gérard TAILLE wrote:
Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . . . . . O O O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | . . . . . . . . . . . . . . . O X O . |
$$ | . . . . . . . . . . . . . . . O X X O |
$$ | . . . . . . . . . . . . . . . O O O O |
$$ | . . . . . . . . . . . . . . . . . O O |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


In normal play black cannot be killed, even if it is white to play.

This is what I wrote above: after 2 W reinforcements, W first seem to kill now (in normal play) by connecting once on either side. B first could create the double ko life. This position seems unsettled.


How white can kill black in normal play?

Click Here To Show Diagram Code
[go]$$W
$$ -----------------------------------------
$$ | . . . . . O O O . . O O X 3 X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X 2 X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X 4 O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | . . . . . . . . . . . . . . . O X O 1 |
$$ | . . . . . . . . . . . . . . . O X X O |
$$ | . . . . . . . . . . . . . . . O O O O |
$$ | . . . . . . . . . . . . . . . . . O O |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #96 Posted: Thu Sep 16, 2021 2:21 pm 
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You are right, I meant preventing the double ko life but B still has at least one local threat, so it is a winnable ko for him. Still not unconditional life though.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #97 Posted: Thu Sep 16, 2021 2:37 pm 
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Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . . . . O . O . . O O X . X O . . . |
$$ | . . . . . O O X O O X O O X X O . O . |
$$ | . . . . . . O X X X X . X . X O . . . |
$$ | . . . , . . O O O O X X X X O O O O O |
$$ | . . . . . . . . . O O O X X X O X X X |
$$ | . . . . . . . . . . . O X . X X . X . |
$$ | . . . . . . . . . . . O O X X X X O X |
$$ | . . . . . . . . . . . . O O O X . O O |
$$ | . . . . . . . . . . . . . . O X X X O |
$$ | . . . , . . . . . , . . . . O O X O . |
$$ | O O O O O O O O O . . . . . . O X O . |
$$ | X X X X X X X X O . . . . . . O X X O |
$$ | X X X X X X X X O . . . . . . O O O . |
$$ | X X X X X X X X O . . . . . . . . O O |
$$ | X X X X X X X X O . . . . . . . . . . |
$$ | O X X , X X X X O , . . . . . , . . . |
$$ | . O X X X X X X O . . . . . . . . . . |
$$ | O O O X X X X X O . . . . . . . . . . |
$$ | . O X . X X X X O . . . . . . . . . . |
$$ ---------------------------------------[/go]


This position with the double ko seki is really strange:
1) In normal play the double ko allows white to avoid black living without condition => black can only force NO RESULT to avoid losing her group.
2) In confirmation phase and J89-pass-once-per-ko it is the contrary : the double ko allows black to live if white add only two moves.
Interesting no?

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #98 Posted: Thu Sep 16, 2021 2:42 pm 
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Interesting yes. I think the right way to analyze this from here would be to create a table, showing the outcome for 0-1-2-3 W reinforcement moves, with and without double ko seki, and for all potential rules (normal play, J89 pass-each-time, J89 pass-once, Korean). Would make a nice and informatible table. :)

Btw life on double ko is known to be vulnerable and potentially become triple ko later, even in simpler positions. Any double ko restricts further ko play, often in an asymmetrical way.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #99 Posted: Thu Sep 16, 2021 3:14 pm 
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jann wrote:
Interesting yes. I think the right way to analyze this from here would be to create a table, showing the outcome for 0-1-2-3 W reinforcement moves, with and without double ko seki, and for all potential rules (normal play, J89 pass-each-time, J89 pass-once, Korean). Would make a nice and informatible table. :)

Btw life on double ko is known to be vulnerable and potentially become triple ko later, even in simpler positions. Any double ko restricts further ko play, often in an asymmetrical way.


Oops, a lot of work ;-)
If you try this work I promise to help you Jann (except for korean rule because I have not enough information concerning Life and Death analysis).
I am happy you found this position interesting because I had to take a lot of time to find it!

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #100 Posted: Thu Sep 16, 2021 3:42 pm 
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No sry, I cannot even imagine doing that much, for a still error-prone table.

But I'd expect it to show some differences between pass-once and pass-each-time here and there. But also that the latter itself would give anomalous result (similarly to lightvector's example) in some cases (like in the original position with 0 W moves) - so even the "correct" ruling could be doubtful.

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