How superko can change a losing position into a winning one

For discussing go rule sets and rule theory
Post Reply
Gérard TAILLE
Gosei
Posts: 1346
Joined: Sun Aug 23, 2020 2:47 am
Rank: 1d
GD Posts: 0
Has thanked: 21 times
Been thanked: 57 times

How superko can change a losing position into a winning one

Post by Gérard TAILLE »

Black to play and win
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!
User avatar
Harleqin
Lives in sente
Posts: 921
Joined: Sat Mar 06, 2010 10:31 am
Rank: German 2 dan
GD Posts: 0
Has thanked: 401 times
Been thanked: 164 times

Re: How superko can change a losing position into a winning

Post by Harleqin »

Why would that be a seki?
A good system naturally covers all corner cases without further effort.
Gérard TAILLE
Gosei
Posts: 1346
Joined: Sun Aug 23, 2020 2:47 am
Rank: 1d
GD Posts: 0
Has thanked: 21 times
Been thanked: 57 times

Re: How superko can change a losing position into a winning

Post by Gérard TAILLE »

Harleqin wrote:Why would that be a seki?
The point is the following: after the sequence
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]
:w2: pass
:b5: on :b1:
:w6: on :b3:
:b7: on :b1:

it follows
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
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
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
Post Reply