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 Post subject: BGA uses natural situational superko?
Post #1 Posted: Wed Jun 03, 2015 2:38 pm 
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The British Go Association claims to use the same rules as the American Go Association, which would imply use of situational superko, but their official rules text says:

Quote:
It is illegal for a player to play so as to recreate a board position of the game, previously created by a play of the same player.

So it seems they are actually using natural situational superko...

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 Post subject: Re: BGA uses natural situational superko?
Post #2 Posted: Wed Jun 03, 2015 2:56 pm 
Judan

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luigi wrote:
The British Go Association claims to use the same rules as the American Go Association

Not quite. They don't claim an exact copy:
britgo.org wrote:
This document is inspired by the AGA's official statement of the rules and our interpretation of those rules.


luigi wrote:
So it seems they are actually using natural situational superko...

Yes, as the authors of the AGA rules intended theirs too as well, but they were imprecise/misinterpreted.


Last edited by Uberdude on Wed Jun 03, 2015 3:00 pm, edited 1 time in total.

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 Post subject: Re: BGA uses natural situational superko?
Post #3 Posted: Thu Jun 04, 2015 4:42 am 
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Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).

In practice, it is extremely likely that the referee will refuse the application of the NSSK rule, arguing that it was "not the intention of the writers of the rule".

Image

Here, with the NSSK rule, all stones are alive, including white's top group and black's A1 chain !!

White passes. If Black J9, then White J8 (absurd move allowed by the NSSK rule !). If Black plays anywhere else, White passes, ensuring that W J8 is always legal after B J9.
If White captures in B3, her top group dies. Black J9, and White J8 is now illegal because it recreates the situation already created by White B3. Therefore Black A1 lives.

As long as White passes, she doesn't create any situation on the board, and all of her subsequent moves are legal, including recapturing in a ko.

See discussion in viewtopic.php?f=45&t=11510


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 Post subject: Re: BGA uses natural situational superko?
Post #4 Posted: Thu Jun 04, 2015 5:26 am 
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Pio2001 wrote:
Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).


Except the BGA rules (http://www.britgo.org/files/rules/rulesofplay.pdf) have rule 6.1:

6.1 Ko
It is illegal for a player to capture a single stone which itself captured a single stone of the same player on the
previous move.

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 Post subject: Re: BGA uses natural situational superko?
Post #5 Posted: Thu Jun 04, 2015 7:39 am 
Honinbo

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Uberdude wrote:
luigi wrote:
The British Go Association claims to use the same rules as the American Go Association

Not quite. They don't claim an exact copy:
britgo.org wrote:
This document is inspired by the AGA's official statement of the rules and our interpretation of those rules.


luigi wrote:
So it seems they are actually using natural situational superko...

Yes, as the authors of the AGA rules intended theirs too as well, but they were imprecise/misinterpreted.


Pio2001 wrote:
Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).

In practice, it is extremely likely that the referee will refuse the application of the NSSK rule, arguing that it was "not the intention of the writers of the rule".

Image

Here, with the NSSK rule, all stones are alive, including white's top group and black's A1 chain !!

White passes. If Black J9, then White J8 (absurd move allowed by the NSSK rule !). If Black plays anywhere else, White passes, ensuring that W J8 is always legal after B J9.
If White captures in B3, her top group dies. Black J9, and White J8 is now illegal because it recreates the situation already created by White B3. Therefore Black A1 lives.

As long as White passes, she doesn't create any situation on the board, and all of her subsequent moves are legal, including recapturing in a ko.

See discussion in viewtopic.php?f=45&t=11510


At this point, AGA players are probably glad that the AGA did not actually adopt the NSSK rule. :mrgreen:

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 Post subject: Re: BGA uses natural situational superko?
Post #6 Posted: Thu Jun 04, 2015 7:40 am 
Honinbo

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HermanHiddema wrote:
Pio2001 wrote:
Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).


Except the BGA rules (http://www.britgo.org/files/rules/rulesofplay.pdf) have rule 6.1:

6.1 Ko
It is illegal for a player to capture a single stone which itself captured a single stone of the same player on the
previous move.


The Lord giveth and the Lord taketh away.

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

Visualize whirled peas.

Everything with love. Stay safe.


This post by Bill Spight was liked by: skydyr
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 Post subject: Re: BGA uses natural situational superko?
Post #7 Posted: Wed Jun 17, 2015 6:37 am 
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Pio2001 wrote:
The use of NSSK allows to immediately recapture in a ko if you passed one move before

I already wasn't a fan of NSSK before (it's needlessly complicated), but after this I don't understand how it can apparently be advocated by some...

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