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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!boulder!bill
From: bill@boulder.Colorado.EDU
Newsgroups: comp.ai,comp.ai.neural-nets
Subject: Re: Parallelism, Real vs. Simulated: A Query
Message-ID: <12449@boulder.Colorado.EDU>
Date: 6 Oct 89 07:31:19 GMT
References: <17820@bellcore.bellcore.com>
Sender: news@boulder.Colorado.EDU
Reply-To: bill@synapse.Colorado.EDU (Bill Skaggs)
Organization: University of Colorado, Boulder
Lines: 26


>I have a simple question: What capabilities of PDP systems do and
>do not depend on the net's actually being implemented in parallel,
>rather than just being serially simulated? Is it only speed and
>capacity parameters, or something more?
>
>Stevan Harnad     (harnad@confidence.princeton.edu)

     A little too simple, maybe, because it isn't quite clear what
it means.  Let me rephrase it, and you can say whether this is
something like what you meant:

     "We have here a black box, with a PDP device inside it and
some user-interface stuff on the surface.  Is it necessarily 
true, ignoring considerations of time and space, that the
PDP device is replaceable by a serial device which from the
user's viewpoint will behave identically?"

     If this is the question, then I think the answer is yes.
Since the PDP device is a physical object, it is governed by a set
of differential equations, and those equations can be solved to any
desired accuracy by a serial device.  (It may take a long time to solve
them, though.)  If the PDP system is chaotic (in the mathematical sense),
then no simulation will ever be able to _duplicate_ its behavior, but
the simulation will still be able to imitate it in the sense of being
equally unpredictable by the user.