Re: [computer-go] Super Ko on KGS ignores player to move

[drd@xxxxxxx]

Hi John,

I'm still not sure about this, but I'm thinking.  

Basically, you are saying that there exists at least 3 different things that 
we might consider as being  a "position" : 

   1.  A board configuration (without regard to color to move)   (PSK)

   2.  A board configuration combined with color to move.        (SSK)

   3.  A "true" position which can't be described by 1 or 2 above.   

A real (or "true") position needs move history to ascertain, not just color to 
move and configuration.

Therefore, you are saying why bother using definition 2 when even this does 
not fully define the "true" position.

Ok, maybe.    I'm not that much against PSK anyway (just a little against -:)
I hate that move history defines a position,  but this is problem with ANY ko 
rule.   

To bad we can't consider repetition a draw, and force the player who has most 
at stake to avoid the repeat.   This would change the nature of the game I'm 
afraid, and we would still have the question of what actually constitutes a 
repeat position SSK or PSK?

- Don


On Monday 15 August 2005 10:10 am, John Tromp wrote:
> drd@xxxxxxxxxxxxxxxxx wrote:
> > Personally,  I  don't like PSK as set in the Tromp/Taylor rules either. 
> > In my personal opinion,  and it's just that I admit,  it detracts
> > slightly from the elegance  of TT rules because it subtracts an element
> > (color to move) from what a position really is.
> >
> > If given an arbitrary Go board configuration to play,  would you care
> > which color you are assigned?   Of course you would!   There is an
> > advantage to having one over the other given any particular configuation.
> >   The same configuration with WHITE to move is a different "position"
> > than the identical configuration with BLACK to move.
> >
> > Tromp/Taylor tries to simplify by introducing the concept of board
> > configuration,  which is an addition.   When you play a game, you never
> > make 2 moves in a row (unless the opponent passes),  because you
> > understand that color to move is part of the "position."     With PSK
> > there has been added a new concept to the game which did not need to
> > exist and detracts slightly from the elegance of the rules.
> >
> > I understand of course that this call be interpreted differently.   I
> > know the Tromp/Taylor designers think this is actually a simplification
> > and they are smarter than I am.
>
> Dear Don,
>
> Let me explain in greater detail why I believe there are very
> good reasons to prefer PSK over SSK.
>
> Your basic argument against PSK is that the simple notion of
> position doesn't entail everything that matters for the future.
>
> While I agree that is correct, I want to argue that the notion
> of position should *shouldn't* entail additional information that
> matters for the future.
>
> Why? because it cannot be taken to its logical extreme.
>
> Consider the position
>
>   X . X
>   O X X
>   . X X
>
> with white to move. I ask you, do you care which color you are assigned?
> Then you say, well, that depends on whether O is allowed to capture the ko.
>
> Reflecting on this, we can see that in fact the entire history matters
> as to which color we prefer.
>
> At the same time it is entirely obvious that a SUPERsuperko rule that takes
> the whole history into account is useless.
>
> The conclusion we must draw as that trying to include information about
> the future into the notion of position is inherently flawed. I consider
> any solution that includes some information while excluding other
> information to be a compromise at best.
>
> Choosing the simplest notion that does what we want in practice seems the
> best solution then.
>
> It is both easier to describe and easier to implement (at least
> conceptually; there is one set of forbidden stone configurations, rather
> than two separate sets).
>
> regards,
> -John
>
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