On Wed, May 03, 2000 at 06:48:11PM -0700, Dana Hedberg wrote:
> Matt Gingell wrote:
> >
> > > > Imagine I could simulate, in real time, a system of 100 atoms using 50
> > > > atoms. I can then have two groups of 50 running in real time with perfect
> > >
> > >Of course, you can't do that. Also, you don't mention which modelling
> > >paradigm you're contemplating, say QM or MD.
> >
> > Exactly - it's like thinking you could emulate a P2 on a P2 and end up with
> > something faster. The implication therefore is that you can't model the whole
> > universe in anything smaller than the whole universe, which is why I don't
> > understand why someone would claim you could simulate everything with a star.
> > Given the constraint of perfect fidelity (if indeed that means anything), then
> > which paradigm you work in is just a bookkeeping issue.
> >
> > -matt
>
> Ok, I have a question that is leaving me confused. What exactly is the
> role of compression within simulation situations? If I can represent
> (i.e., model) a set of information perfectly with a compressed form of
> that information, then haven't I modeled something larger with something
> smaller?
You can store a state of the model in compressed form; you can work on
the compressed version too (perhaps expanding parts in turn to work
on).
> For example: I can model 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 with 2 *
> 5. I've compressed a ten digit, multiple addition operation with a
> single multiplication of two digits operation.
>
> This would then seem to scale up for many things, indeed, even to the
> size of the universe. Is there something I'm missing here?
I think you probably get caught out by a practicality - that although a
particular state of your simulated universe may be compressible enough
to store, with the savings afforded by compression making enough room
for your simulation and compression code, there will always be some
complicated states of the simulated universe which will not compress
sufficiently. Compress 1 + 1.... to 2 * 5. Compress 2 * 5... to 10.
Now compress 137329.13759712722327137211872722334816576157 and leave
enough space for your code when you're done.
Oooh... what if the computer running our universe was relying on the
fact it compressed it all - if things get too complicated, *poof* ...?
Martin
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