Re: [computer-go] can superko lead to zugzwang?

[Erik van der Werf <E.vanderWerf@xxxxxxxxxxxxx>]

Arthur Cater wrote:

> Hi folks,
> As I understand it, superko means that it is not permitted for
> the same situation to be repeated: stones on the board, player to
> move, and (I presume) balance of prisoners.
>
> I wonder if it can happen therefore that a player can find himself
> /forced/ to make a non-pass move.

Yes and no. It depends on what you mean by "forced". If you mean that 
it's the only legal option the answer should be no because passing 
should always be legal to end the game. (Notice that I write "should" 
because I would not be surprised if some rule texts when interpreted 
literally might say otherwise.)

If you mean "forced" in a slightly weaker sense such as that passing 
would lead to an unacceptable result by superko, and that an 'inferior' 
move has to be made (which would be inferior under all major rule sets) 
to prevent this, then the answer is yes.

Here's a non-trivial example (stelling 3 of my thesis).

. O O # # # O O .
O . O # . # O O #
O O # . # O O # .
# # # # # O O # #
O O O O # # O O .
. . O # # # # O O
O O # # O O O # O
O . O # O . O # #
O . O # O O . # .

9x9 board, superko, area scoring, 6 komi for White
It does not matter who plays first.

Have fun,
Erik

PS If you scroll down for there's a hint.

































































































White's 'unconditionally alive' group in the upper left corner is dead.

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