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How superko can change a losing position into a winning one
Posted: Tue Sep 01, 2020 1:30 pm
by Gérard TAILLE
Black to play and win
$$B
$$ -----------
$$ | O . a . O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------
- Click Here To Show Diagram Code
[go]$$B
$$ -----------
$$ | O . a . O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------[/go]
I suppose we are using AGA rule (SSK) on a 5x5 board.
The problem I propose is the following:
Starting with an empty board, what is the minimum number of moves you need to build the above position such that black can play and win.
Note : if for example you play 44 moves (22 pass for black + 22 white stones played by white) then the above position is a losing one for black because after a black move on "a" the position looks like a strange seki with only one black stone involved! Is this is true then it is a large win for white.
You have to find something else and minimise the number of moves!
Re: How superko can change a losing position into a winning
Posted: Tue Sep 01, 2020 3:43 pm
by Harleqin
Why would that be a seki?
Re: How superko can change a losing position into a winning
Posted: Wed Sep 02, 2020 1:48 am
by Gérard TAILLE
Harleqin wrote:Why would that be a seki?
The point is the following: after the sequence
$$B
$$ -----------
$$ | O 3 1 4 O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------
- Click Here To Show Diagram Code
[go]$$B
$$ -----------
$$ | O 3 1 4 O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------[/go]
pass
on
on
on
it follows
$$Wm8
$$ -----------
$$ | . . X . . -
$$ | . . . . . -
$$ | . . 1 . . -
$$ | . . . . . -
$$ | . . . . . -
$$ -----------
- Click Here To Show Diagram Code
[go]$$Wm8
$$ -----------
$$ | . . X . . -
$$ | . . . . . -
$$ | . . 1 . . -
$$ | . . . . . -
$$ | . . . . . -
$$ -----------[/go]
and here my impression is that black cannot live somewhere on the board. Maybe I am not strong enough to show this and I hope stronger player will be able to confirm my impression.
If it is true the position is seki because after
$$B
$$ -----------
$$ | O 2 1 3 O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------
- Click Here To Show Diagram Code
[go]$$B
$$ -----------
$$ | O 2 1 3 O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ | O O O O O -
$$ -----------[/go]
we reach the position
$$Wm4
$$ -----------
$$ | . . X X . -
$$ | . . . . . -
$$ | . . 1 . . -
$$ | . . . . . -
$$ | . . . . . -
$$ -----------
- Click Here To Show Diagram Code
[go]$$Wm4
$$ -----------
$$ | . . X X . -
$$ | . . . . . -
$$ | . . 1 . . -
$$ | . . . . . -
$$ | . . . . . -
$$ -----------[/go]
and now it appears to me that black can live with a better result than the initial position after black 1