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From: israel@umcp-cs.UUCP
Newsgroups: net.ai
Subject: Re: Parallelism and Conciousness
Message-ID: <3498@umcp-cs.UUCP>
Date: Tue, 1-Nov-83 01:39:06 EST
Article-I.D.: umcp-cs.3498
Posted: Tue Nov  1 01:39:06 1983
Date-Received: Fri, 4-Nov-83 00:27:38 EST
References: <13089@sri-arpa.UUCP> <3489@umcp-cs.UUCP>
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 50


	From: speaker@umcp-cs.UUCP
	
		No algorithm is inherently parallel.
	
	The algorithms you are thinking about occur in the serial world of
	the Turing machine.  Turing machines, remember, have only only one
	input.  Consider what happens to your general purpose turing machine
	when it must compute on more than one input and simultaneously!
	
	So existence in the real world may require parallelism.

How do you define simultaneously?  If you mean within a very short
period of time, then that requirement is based on the maximum speed of
a processing unit that we can currently build.  If you mean 'at the
exact same time', then I defy you to show me a case where this is
necessary.

The statement "No algorithm is inherently parallel", just means that
the algoritm itself (as opposed to the engineering of putting it
into practice) does not necessarily have to be done in parallel.
Any parallel algorithm that you give me, I can write a sequential
algorithm that does the same thing.

Now, if you assume a finite number of processors for the parallel
algorithm, then the question of whether the sequential algorithm will
work under time constraints is dependent on the speed of the
processor worked on.  I don't know if there has been any work
done on theoretical limits of the speed of a processor (Does
anyone know? is this a meaningful question?), but if we assume
none (a very chancy assumption at best), then any parallel algorithm
can be done sequentially in practice.

If you allow an infinite number of processors for the parallel
algorithm, then the sequential version of the algorithm can't
ever work in practice.  But can the parallel version?  What
do we run it on?  Can you picture an infinitely parallel
computer which has robots with shovels with it, and when the
computer needs an unallocated processor and has none, then
the robots dig up the appropriate minerals and construct
the processor.  Of course, it doesn't need to be said that
if the system notices that the demand for processors is
faster than the robots' processor production output, then
the robots make more robots to help them with the raw materials
gathering and the construction.  :-)
-- 

^-^ Bruce ^-^

University of Maryland, Computer Science
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