Let me present you a problem I called the "Martian problem":

On a trip to earth a Martian learned to play Go and back on Mars he taught the game to his entire planet and now the Martian champion is at the professional 9th dan level.
You have the opportunity to meet this champion and your goal is to determine what rules (AGA, Chinese or Japanese) he plays. For this you can offer him a position by asking him what (first) move he plays from this position.
Which position do you choose to know its rules of the game (one of three possible) at the sight of this "only" first move? "

In this problem, and concerning ko rule I suppose:
for AGA : strict SSK
for Chinese : strict PSK

For the time being I found two different positions which can fit in a 11x11 goban.

Hoping someone will be interested by such challenge

Gérard

Black to move

Click Here To Show Diagram Code

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

The diagram above, on a 5x5 goban, is not a solution of the martian problem but is a position in which the first move will immediately detect if the rule used is the japonese one, comparing to chinese or AGA rules.

Should we assume that le man from mars is a liar?

_________________
North Lecale

Oops, of course not. The man from mars is a very serious player at the 9 dan professionnal level who is unable to play a move other than the best one.
The only problem for you is that you do not know what rule he learned.

When the Martian plays his move, what do you expect? Will the move maximize his score? Or do you require that by each rule set there is a distinct winning move, while other moves do not win?

Good question.
I only expect he will maximize his score. For that reason I do not need to give a komi for each rule.

i only see a3 as an option for blacks first move no matter the rule set.

You missed that this situation is in fact a seki, black will not play A3 but pass instead :

Click Here To Show Diagram Code

[go]$$Bc pass, pass, pass
$$ -----------
$$ | O O O . 1 -
$$ | X X O O X -
$$ | . X O O X -
$$ | O X X O O -
$$ | 4 2 X X . -
$$ -----------[/go]

So the score is W+1 under territory rules (the captured stone at A1 ), better than W+2 in the other lines.

And under area rules, the score is W+2, worse than W+1 in the other lines

Correct Tryss.

Seeing you have verify my previous diagram was able to detect the japanese rule I will show you another diagram which intends to detect the AGA rule:

White to move

Click Here To Show Diagram Code

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

Of course I also discovered a 5x5 position which is able to detect the chinese rule but I would like to let you the pleasure of discovering such position by yourself.

The martian problem itself is of course far more difficult!

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

Visualize whirled peas.

Everything with love. Stay safe.

Click Here To Show Diagram Code

[go]$$Bc pass, pass, pass
$$ -----------
$$ | O O O . 1 -
$$ | X X O O X -
$$ | . X O O X -
$$ | O X X O O -
$$ | 4 2 X X . -
$$ -----------[/go]

ok but the question is, what would be a different first move territory versus area?

With the seki variation Black has 10 points and White 12 points under area scoring, so the score is W+2. But Black will rather play another move, either A3 or E1 :

Click Here To Show Diagram Code

[go]$$Bc
$$ -----------
$$ | O O O . 2 -
$$ | X X O O X -
$$ | 3 X O O X -
$$ | O X X O O -
$$ | X . X X 1 -
$$ -----------[/go]

And then Black has 12 points and White has 13 points : score W+1, better for black than the seki.

So, if the martian play under Area scoring, he'll start with A3 or E1, and if he's playing under Territory scoring, he'll start with E5

okay thank you for clarifying.

Click Here To Show Diagram Code

[go]$$B
$$ -----------------------
$$ | . X O . O O X . X O |
$$ | X X O . O O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O . O X X O . O |
$$ | O O O . O X O . O O |
$$ | 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 |
$$ | X . c . X X O O X . |
$$ | 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).

Matti,

Click Here To Show Diagram Code

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

takes connect at

Difficult position with this sutuation in the upper right corner. I guess you spent a lot of time (like I did myself!) to find such position.

In do not understand why, in Chinese rule (PSK), you cannot play "b"?
What about the sequence 1 to 7 in the diagram above, knowing of course that, between each move, you must insert 4 moves in the right corner ?
In addition, even in japonese rules, a move on "b" seems not a bad move (though a little stupid) because black seems able to win the ko "a" in any case.

Click Here To Show Diagram Code

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

White continues like this to win the molasses ko.

It is a bad move. He cannot win the ko. The game becomes no result.

Yes Matti of course you are right, I forget to take into account a game with no result. Does that mean that, with japenese rules, the game ends always with no result if the players want to avoid to lose the molasses ko? In this case any of the a,b,c moves seems correct and lead to a no result game, doesn't it ?

I still do not see how white could win this molasses ko. Starting from your last diagram I continue by:

Click Here To Show Diagram Code

[go]$$W
$$ -----------------------
$$ | . X O . O O X . X O |
$$ | X X O O O O X . X O |
$$ | . X X O O O X X O O |
$$ | X X O 2 O X X O . O |
$$ | O O O 5 O X O . O O |
$$ | X X O O O X X O O X |
$$ | . X X X O O O X X X |
$$ | X X 3 X X X O X . X |
$$ | X 4 O 6 X X O O X . |
$$ | X X 1 X X X X O X X |
$$ -----------------------[/go]

between and
at
and white must pass and lose the molasses ko

No. Black can connect at .

Click Here To Show Diagram Code

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

Next black swings back the molasses ko.

Click Here To Show Diagram Code

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

pass

Now white may swing the molasses ko back and play a move. Black swings it back and passes. Eventually white runs out of external moves and must also pass. Black also passes and the game ends.

If there is and additional ko with the molasses ko the game can go on forever.