The problem seems to be a misunderstanding of japonese rules.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X O . O |
$$ | X X O O O O X O . O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X O 1 O |
$$ | O O O . O X . X O O |
$$ | X X O O O X X O O 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 X O X X |
$$ -----------------------[/go]

In the situation above my understanding is that after black white pass, black pass white, in order to avoid losing the game can claim to play in the molasses ko.


Maybe I am wrong but it looks like the following example:

Click Here To Show Diagram Code

[go]$$B
$$ ------------
$$ | 1 O O . O|
$$ | O X O O .|
$$ | X X X O O|
$$ | . X X X X|
$$ | X X X X X|
$$ ------------[/go]

In this situation do we have to conclude (in japonase rule) that is a winning move or is white allowed to retake the ko after two passes?

I had to revise the situation. White has just captured with circled stone.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X . X O |
$$ | X X O c . O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O . O X X O . O |
$$ | O O O . O X W . O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X . X X b O X . X |
$$ | X . . . X X O O X . |
$$ | X X . X X a X O X X |
$$ -----------------------[/go]

Black to play. I think, a is best with japanese rules. b is best with AGA rules (SSK) and c is best with Chinese rules (PSK).

Oops my last diagramm was not correctly built. Here is a new one.

Click Here To Show Diagram Code

[go]$$B
$$ ----------------
$$ | 1 O O O . O .|
$$ | O X X O O O O|
$$ | X X X X O O O|
$$ | X X X X O X X|
$$ | X X X O O X .|
$$ | X X X O X . X|
$$ | . X X O X X .|
$$ ------------[/go]

After two consecutive passes, White can require that play resume, but only with Black to play. Then the resumption might go like this.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X O 3 O |
$$ | X X O O O O X O 1 O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X 2 X O |
$$ | O O O . O X 4 X O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X X X X O O X . X |
$$ | X . X 5 X X O O X . |
$$ | X X . X X X X O X X |
$$ -----------------------[/go]

= pass

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X . X O |
$$ | X X O O O O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X O . O |
$$ | O O O . O X O 7 O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X X X X O O X . X |
$$ | X . X X X X O O X . |
$$ | X X . X X X X O X X |
$$ -----------------------[/go]

And White is embarrassed.

However, White can claim that the Black stones in the molasses ko are dead. The hypothetical play would go like this.

Click Here To Show Diagram Code

[go]$$W Black dies, hypothetically
$$ -----------------------
$$ | . X O . O O X O . O |
$$ | X X O O O O X O 2 O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X 1 X O |
$$ | O O O . O X 3 X O O |
$$ | X X O O O X X O O 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 X O X X |
$$ -----------------------[/go]

In this case if and both pass, White can claim that Black is dead. Hypothetical play could go this way.

Click Here To Show Diagram Code

[go]$$W
$$ ----------------
$$ | X O O O . O .|
$$ | 1 X X O O O O|
$$ | X X X X O O O|
$$ | X X X X O X X|
$$ | X X X O O X .|
$$ | X X X O X . X|
$$ | 3 X X O X X .|
$$ ------------[/go]

= pass

Click Here To Show Diagram Code

[go]$$W
$$ ----------------
$$ | . O O O . O .|
$$ | O . . O O O O|
$$ | . . . . O O O|
$$ | . . . . O X X|
$$ | . . . O O X .|
$$ | . . . O X . X|
$$ | O . . O X X .|
$$ ------------[/go]

The Black stones are dead unless Black to play can make a living group on this board, assuming correct play.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Hi Bill,

I am not sure to understand the japonese rule !

Click Here To Show Diagram Code

[go]$$B
$$ ----------------------------------------
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X .|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X O|
$$ | X X X X X X X X X X X X X X X X X O 1|
$$ | X X X X X X X X X X X X X X X X X O O|
$$ | X X X X X X X X X X X X X X X X O O .|
$$ | X X X X X X X X X X X X X X X X O . O|
$$ ----------------------------------------[/go]

In the position above you can see 349 black stones against 8 white stones and I suppose 341 white stones were killed.
After black , pass, pass what is the result ?
Can white claim at retaking the ko, killing a lot of black stones and expecting winning easily the resulting position ?

I begin to see your idea Matti and I suspect you will manage to distinguish AGA and Chinese rules though this new version seems not to work.

In chinese rule I think a play at "b" is still correct with the following sequence (you have always to insert between each move the molasses ko moves)

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O 4 O O X . X O |
$$ | X X O 3 . O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O 7 O X X O . O |
$$ | O O O . O X O . O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X 8 X X 1 O X . X |
$$ | X 9 2 . X X O O X . |
$$ | X X 6 X X 5 X O X X |
$$ -----------------------[/go]

and you see that white will finally be the first to pass.

Concerning japonese rule I do not see how you will solve the problem because almost any move is correct, leading to a "no result" game (but, for the time being, I am not sure of my understanding of japonese rule !)

In addition the martian problem is supposed to start with a position ignoring all the previous moves. As a consequence you cannot make the assomption that a move is unplayable due to a ko.

Click Here To Show Diagram Code

[go]$$B
$$ ----------------------------------------
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X .|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X C|
$$ | X X X X X X X X X X X X X X X X X O B|
$$ | X X X X X X X X X X X X X X X X X O O|
$$ | X X X X X X X X X X X X X X X X O O .|
$$ | X X X X X X X X X X X X X X X X O . O|
$$ ----------------------------------------[/go]

In hypothetical play White can take and fill the ko, so the stone is dead. That means that the point is a dame, which means that the rest of the Black stones are in seki, which means that Black has no territory. (OC, Black has 342 prisoners and wins the game, anyway. )

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

You didn't state this in the problem.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X . X O |
$$ | X X O c . O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O . O X X O . O |
$$ | O O O . O X W . O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X X X X b O X . X |
$$ | X . . . X X O O X . |
$$ | X X . X X a X O X X |
$$ -----------------------[/go]

With japanese rules in hypothetical play the circled white stones can also be calied dead.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X W 3 O |
$$ | X X O O O O X W 1 O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X 2 B O |
$$ | O O O . O X 4 B O O |
$$ | X X O O O X X O O 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 X O X X |
$$ -----------------------[/go]

The circled black stones would also be dead and also the big white group in upper right corner. Dead stones cannot surround territory, so there is territory for neither white nor black. Dead stones may only be removed from territory, so no stones would be removed from the upper right corner.

The simple answer is "yes". The reasoning is somewhat subtle. White may try two things.

First Approach: After White passes, black passes. White tries to claim that the whole black stones are dead. The problem is that, even though White can capture all black stones in the hypothetical play, Black may play at the upper left corner to create a stone White cannot capture. Thus the Black group is not dead by the rule. This is not the right approach.

Second approach: After White passes, black passes. The game temporarily stops but White can request the resumption of the game. Black will play first, but has nothing to do, and White will eventually capture all Black stones. Now, be careful that Black can keep playing as if almost a new game stared. Depending on the captured stone numbers and komi, Black may still have a chance to win. Anyway, this is a better result than the first approach.

_________________
Jaeup Kim
Professor in Physics, Ulsan National Institute of Science and Technology, Korea
Author of the Book "Understanding the Rules of Baduk", available at https://home.unist.ac.kr/professor/jukim/bbs/board.php?bo_table=notice&wr_id=5

Indeed there are some misunderstandings on the fate of the molasses ko in the Japanese rule. This shape has never been judged in the three Asian rules, and I am sure the rulemakers have never thought of this shape, but here is one basic principle of the Korean/Japanese rule worth remembering: the whole board repetition other than the simple ko recapture is not prohibited. The sequence repeating the whole board position includes passes, but the rule also does not prohibit it.

Thus, if it occurs in a major tournament game, I believe the likely result is a draw (or no result if the term matters). I have not talked with someone in Nihon Ki-in, but at least the Korean pros I have talked with (including those who wrote the Korean rule) agreed that a draw is the proper result for this shape. (Thinking of the way the Chinese rule has been applied in reality, I think they will also rule it a draw.)

The situation can be quite complicated in that until almost the last moment, the players have no reason to pass, and the whole board does not repeat. Unless the rule allows the players to "anticipate the whole board repetition and stop the game", due to the molasses sequence, the game may continue for 24 hours until the draw finally occurs.

_________________
Jaeup Kim
Professor in Physics, Ulsan National Institute of Science and Technology, Korea
Author of the Book "Understanding the Rules of Baduk", available at https://home.unist.ac.kr/professor/jukim/bbs/board.php?bo_table=notice&wr_id=5

@Gérard TAILLE



Jaeup is right. Since I had already talked about reopening the play and you had not mentioned it, I thought you were asking about the result with hypothetical play, which is rather strange.

Edit: Let me reconsider. Black took the ko and then each player passed in turn. Now White requires resumption of play, with Black to play first. Black passes. But the ko ban is still in effect, so White must pass, as well. The play is over.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Now passes for the ko at 4. Play continues.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X 8 B O |
$$ | X X O O O O X 6 B O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X W . O |
$$ | O O O . O X W 7 O O |
$$ | X X O O O X X O O 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 X O X X |
$$ -----------------------[/go]

But now, since Black has not passed for the second ko she cannot take it and White can capture all the Black stones in the molasses ko.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Yes Matti, of course I realize that I did not mentionned this point, sorry for that.

Anyway, taking your point into account, I looked for this version of the martian problem and I concluded that this new problem is far easier that the original one, though it is quite interesting. Instead of just excluding a move due to a simple ko you can also chose to exclude a move due to a superko.
With this in mind I built the following solution:

White to play

Click Here To Show Diagram Code

[go]$$W
$$ ------------
$$ | . . O O O |
$$ | O O O O O |
$$ | O O X X X |
$$ | . O X X X |
$$ | O X X X . |
$$ -------------[/go]

starting from this position white captures all black stones and continue until position:

Click Here To Show Diagram Code

[go]$$W
$$ ------------
$$ | O O O O O |
$$ | O O O O O |
$$ | O O O O O |
$$ | . O O O O |
$$ | O O O O O |
$$ -------------[/go]

here black captures all white stones and now you can build the following very simple martian position

Black to play

Click Here To Show Diagram Code

[go]$$W
$$ -------------
$$ | . . O O O |
$$ | O O O O O |
$$ | O O X X X |
$$ | X O X X X |
$$ | a X b X . |
$$ -------------[/go]

japonese rule : black must pass to avoid giving an additional prisoner
AGA rule : black must play "a" to save its stones and reach soon a seki
chinese rule : black must play "b" to reach an immediat seki because white cannot answer "a" due to superko

Note : for the original martian problem I searched for a solution with a molasses ko but I had to give up. The two solutions I found do not use this molasses ko scheme.

Oops now I need really help because it is obvious I am not mastering japonese rule subtilities!
It seems that the right procedure for white is to requires resumption of play, with black to play, but after black passes it looks now unclear to know if ko ban is still in effect or not? What is the correct interpetation?

I'm not sure it's this simple. Japanese rules only allow resuming a game with the opponent's move, so one side (who is interested in this) may omit the molasses move and pass instead after the opponent's pass (late when no other plays). So whether the repetition necessarily infinite depends on hypothetical play and status?

AFAIK all non-superko rules in use today allow ko recapture after pass - only immediate ko recapture is prohibited.

Jann, during the course of a game I have the same interpretation of the article (I hope I caught the right rule!)

Article 6. Ko
A shape in which the players can alternately capture and recapture one opposing stone is called a "ko." A player whose stone has been captured in a ko cannot recapture in that ko on the next move.

but the point here concerns the resumption of the game. The corresponding article is the following:

Article 9. End of the game
1. When a player passes his move and his opponent passes in succession, the game stops.
2. After stopping, the game ends through confirmation and agreement by the two players about the life and death of stones and territory. This is called "the end of the game."
3. If a player requests resumption of a stopped game, his opponent must oblige and has the right to play first.

and for me there is an ambiguity in the wording "his opponent must oblige and has the right to play first".

Click Here To Show Diagram Code

[go]$$B
$$ ----------------------------------------
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X .|
$$ | X X X X X X X X X X X X X X X X X X X|
$$ | X X X X X X X X X X X X X X X X X X O|
$$ | X X X X X X X X X X X X X X X X X O 1|
$$ | X X X X X X X X X X X X X X X X X O O|
$$ | X X X X X X X X X X X X X X X X O O .|
$$ | X X X X X X X X X X X X X X X X O . O|
$$ ----------------------------------------[/go]

After , pass, pass how can we resume the play when white call for a resumption of the game ?
It is written that the opponent (black) has the right to play first. Here is the point. A right is not an obligation and black may decide to let white moving first and in this case the ko remains active!
In the other hand if black were "obliged" to play she will be forced to pass and the ko will no more be active.
Great difference isn't it?

B has the right to move first in resumption. He may pass this move. In any case any potential later move is not recapturing in the ko on the NEXT move (ie. after the original ko capture). This would be true even if W had the first move in resumption because of the two intervening passes.

This kind of problem (no ko recapture unless the board changed) is only characteristic for most superko variants.

That sounds like a good and fair conclusion. White is then able to retake the ko with a great chance of winning the game.

BTW, coming back to molasses ko in japonese rule:

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X O . O |
$$ | X X O O O O X O . O |
$$ | . X X O O O X X O O |
$$ | X X O O O X X O 1 O |
$$ | O O O . O X . X O O |
$$ | X X O O O X X O O 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 X O X X |
$$ -----------------------[/go]

My undertanding is now the following : after black , white passes, black cannot pass whithout losing her stones in the upper right corner. Black is forced to continue the game and, because the situation is the same for white, this is an infinite loop and a no result game.