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 Post subject: How superko can change a losing position into a winning one #1 Posted: Tue Sep 01, 2020 1:30 pm
 Lives with ko

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Rank: 1er dan
Black to play and win
`[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!

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 Post subject: Re: How superko can change a losing position into a winning #2 Posted: Tue Sep 01, 2020 3:43 pm
 Lives in sente

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Why would that be a seki?

_________________
A good system naturally covers all corner cases without further effort.

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 Post subject: Re: How superko can change a losing position into a winning #3 Posted: Wed Sep 02, 2020 1:48 am
 Lives with ko

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Harleqin wrote:
Why would that be a seki?

The point is the following: after the sequence

`[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

`[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

`[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

`[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

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