Life In 19x19

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[go]$$W White to play
$$ --------------
$$ | O X . X X |
$$ | . O X X X |
$$ | O O X X X |
$$ | X X X . X |
$$ | X X X X . |
$$ -------------[/go]

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[go]$$W White to play
$$ --------------
$$ | O X 1 X X |
$$ | . O X X X |
$$ | O O X X X |
$$ | X X X . X |
$$ | X X X X . |
$$ -------------[/go]

pass
pass

What is the reult of the game after the two passes, depending of the rule ?
For japonese rule it seems clear that white group is dead.
But what about Chinese and AGA rules?

In an informal game with informal rules clearly the white group is dead. Black has two eyes and white cannot make two eyes or seki.

AGA makes this alive I think. Chinese with its special ko rule probably doesn't.

The question is OC whether ko can be retaken after pass.

jann wrote:AGA makes this alive I think. Chinese with its special ko rule probably doesn't.

The question is OC whether ko can be retaken after pass.

Yes Jann, I am not sure of my understanding of japonese rule concerning ko after one or two passes:

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[go]$$W White to play
$$ ------------
$$ | O X . X . .
$$ | . O X X . .
$$ | O O X X . .
$$ | X X X . . .
$$ | . . . . . .
$$[/go]

Let's assume it happens :

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[go]$$W White to play
$$ ------------
$$ | O X 1 X . .
$$ | . O X X . .
$$ | O O X X . .
$$ | X X X . . .
$$ | . . . . . .
$$[/go]

pass
pass

Edit: The question is a pure therotical question on the rule. After the two passes is black allowed to resume the game? If yes I suppose it is white to play first, and white pass again! Now, can Black retake the ko and continue "normally" the game? It looks quite unclear for me when reading the rule.

Japanese rules may be relatively problem-free here (as most rules except strict superko). IIRC resumption is defined and should be possible.

Whether the ko can be retaken after pass (in normal play) is not completely clear but may be guessed as passing for a ko (then retake it) is also the basis in hypothetical play.

jann wrote:Japanese rules may be relatively problem-free here (as most rules except strict superko). IIRC resumption is defined and should be possible.

Whether the ko can be retaken after pass (in normal play) is not completely clear but may be guessed as passing for a ko (then retake it) is also the basis in hypothetical play.

The only reference to "resumption" I found in the rule is in the Article 9.3:

3. If a player requests resumption of a stopped game, his opponent must oblige and has the right to play first.

This is not a defintion of resumption and thus the rule seems to me really unclear on that point (I mean retaking a ko immediatly after pass moves), even if I undersatng your guessing.

What is really the purpose of the resumption? Is it only for resolving some disagreements between the two players on the status of some group of stones, or could it be really a strategic mean to retake a ko by using a pass as a ko threat?

Any other ideas from other experts on japonese rule?

Gérard TAILLE wrote:

jann wrote:Japanese rules may be relatively problem-free here (as most rules except strict superko). IIRC resumption is defined and should be possible.

Whether the ko can be retaken after pass (in normal play) is not completely clear but may be guessed as passing for a ko (then retake it) is also the basis in hypothetical play.

The only reference to "resumption" I found in the rule is in the Article 9.3:

3. If a player requests resumption of a stopped game, his opponent must oblige and has the right to play first.

This is not a defintion of resumption and thus the rule seems to me really unclear on that point (I mean retaking a ko immediatly after pass moves), even if I undersatng your guessing.

What is really the purpose of the resumption? Is it only for resolving some disagreements between the two players on the status of some group of stones, or could it be really a strategic mean to retake a ko by using a pass as a ko threat?

Any other ideas from other experts on japonese rule?

Let's take the following non uncommon situation

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[go]$$W White to play
$$ ----------------
$$ | . O X . X O . .
$$ | O O O X X O . .
$$ | . O X X O O . .
$$ | O X . X O . . .
$$ | X X X X O . . .
$$ | O O O O O . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$[/go]

The common understanding here is that it is locally a seki, and globally both player have an infinity of ko threats.
If now you are allowed to use a pass as a ko threat, and assuming neither player can afford to loose her group, then the game cannot be stopped and we will reach a no result game. That means that the game has changed completly doesn't it?
If it is true then you have to conclude that the ressumption of the game means that you resume the game by just ignoring the last two passes. That way you cannot retake the ko and the result of the position is what is expected (seki and an infinite number of ko threats for both players).

Not clear what the good interpretation is!

Gérard TAILLE wrote:If now you are allowed to use a pass as a ko threat, and assuming neither player can afford to loose her group, then the game cannot be stopped and we will reach a no result game.

Cannot be stopped? Two passes always stop the game (periodically in case of more than one resumption).

No result would mean there is a repetition that neither player can deviate from. This is not the case here (only one side tries to prolong). And there is no real repetition, since the number of resumption requests cannot be infinite (otherwise the losing player would always request resumption in any position). This is also not explicitly spelled out but seems trivial.

jann wrote:

Gérard TAILLE wrote:If now you are allowed to use a pass as a ko threat, and assuming neither player can afford to loose her group, then the game cannot be stopped and we will reach a no result game.

Cannot be stopped? Two passes always stop the game (which could happen periodically in case of more than one resumptions).

No result would mean there is a repetition that neither player can deviate from. This is not the case here (only one side tries to prolong). And there is no real repetition, since the number of resumption requests cannot be infinite (otherwise the losing player would always request resumption, in any position). This is also not explicitly spelled out but still seems trivial.

My understanding is the following (maybe I am wrong): after two passes any player can always request a resumption of the game. In that case the opponent player will play first. If this first player do not pass the game continue normally.
What happens if the first player passes? If the second player passes again then the game is definetly stopped (I mean no new resumption is possible).
Otherwise the game continue normally (I mean a new resumption may happen later).

Click Here To Show Diagram Code

[go]$$B Black to play
$$ ----------------
$$ | . O X . X O . .
$$ | O O O X X O . .
$$ | . O X X O O . .
$$ | O X . X O . . .
$$ | X X X X O . . .
$$ | O O O O O . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$[/go]

Assume for example black to play and black is behind in the game

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[go]$$B Black to play
$$ ----------------
$$ | . O X 2 X O . .
$$ | O O O X X O . .
$$ | 1 O X X O O . .
$$ | O X . X O . . .
$$ | X X X X O . . .
$$ | O O O O O . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$[/go]

pass
pass
after the two passes, black can request a resumption and white plays first and passes:

pass
now if black is allowed to retake the ko then

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[go]$$Bcm7 Black to play
$$ ----------------
$$ | . O 1 O X O . .
$$ | O O O X X O . .
$$ | X O X X O O . .
$$ | 2 X . X O . . .
$$ | X X X X O . . .
$$ | O O O O O . . .
$$ | . . . . . . . .
$$ | . . . . . . . .
$$[/go]

pass
pass
and what in the rule prevents black to resume again the game?
If nothing exists in the rule then we have a loop which implies a no result game.

Edit : it looks like a superko but superko is not handled here in japonese rule.

Gérard TAILLE wrote:and what in the rule prevents black to resume again the game?
...
What happens if the first player passes? If the second player passes again then the game is definetly stopped (I mean no new resumption is possible).

I never heard of such rule (4 passes) in Japanese rules. Again, AFAIK it is not explicitly spelled out where and how the limit is (can resume 1 time, 10 times or what), but obviously B can not request resumption an infinite times. Otherwise in any normal end position the losing side would resume infinitely.

jann wrote:

Gérard TAILLE wrote:and what in the rule prevents black to resume again the game?
...
What happens if the first player passes? If the second player passes again then the game is definetly stopped (I mean no new resumption is possible).

I never heard of such rule (4 passes) in Japanese rules. Again, AFAIK it is not explicitly spelled out where and how the limit is (can resume 1 time, 10 times or what), but obviously B can not request resumption an infinite times. Otherwise in any normal end position the losing side would resume infinitely.

OC I agree that the resumption procedure is not very well defined
Without knowing what is the correct interpretation, do you agree that, in any case, the loop cannot exist if the pass cannot be considered as a ko threat?
Do you know what was really the purpose of the resumption procedure (at the time the rule has been written i.e. in 1989)? What was the problem to solve?

jann wrote:

Gérard TAILLE wrote:and what in the rule prevents black to resume again the game?
...
What happens if the first player passes? If the second player passes again then the game is definetly stopped (I mean no new resumption is possible).

I never heard of such rule (4 passes) in Japanese rules. Again, AFAIK it is not explicitly spelled out where and how the limit is (can resume 1 time, 10 times or what), but obviously B can not request resumption an infinite times. Otherwise in any normal end position the losing side would resume infinitely.

I have already seen these 4 passes in https://senseis.xmp.net/?Flower%2FUnlimitedPhases but I do not know the value of such article for the official rule.

Gérard TAILLE wrote:do you agree that, in any case, the loop cannot exist if the pass cannot be considered as a ko threat?

Not without a 4-pass rule, which is (AFAIK) nonexistent in Japanese. The "loop" would still work without making any board play, just requesting resumption again and again, in any position.

Even with a 4-pass rule no pass as ko threat would contradict hypothetical play and would raise the original 1-eye problem. That is not the correct direction.

Do you know what was really the purpose of the resumption procedure (at the time the rule has been written i.e. in 1989)?

I don't know the specifics but I think resumption exists in most rulesets and is rather common. For Japanese it may be especially important since it must be able to reach a position that is acceptably scorable. So missed moves, forgotten teire, "changed my mind" or whatever reason adding few moves after an earlier pass can affect LD and hypothetical play as well.

jann wrote: Even with a 4-pass rule no pass as ko threat would contradict hypothetical play and would raise the original 1-eye problem. That is not the correct direction.

Oops I am not talking about "hypothetical play". I am talking only about the "normal" play. If I understand correctly, when resumption occurs the game continue normally. The hypothetical play begins only after the end of "normal" play i.e. after two passes and with no more resumption.

The only concerns with the rule is to understand how we can avoid a loop due to resumption.
I perfectly know that the rule do not mentionned 4 passes. It is only common sense: if you request resumption but you only pass (after a new pass of your opponent) then the "normal" game is over and "hypothetical play" may begin.
Without this 4 passes (here again I know it is not specified explicitly in the rule) you have to specify when you decide a resumption is no more allowed. What would be your proposal?

Gérard TAILLE wrote:Oops I am not talking about "hypothetical play". I am talking only about the "normal" play.

I understand, but I doubt you can have a different opinion about whether passes work as a ko threat in one and in the other.

you have to specify when you decide a resumption is no more allowed. What would be your proposal?

I don't have have, except using common sense (no infinite resumptions).