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From: johnw@astroatc.UUCP
Newsgroups: comp.arch
Subject: Re: chewing up mips with graphics [parallel computing]
Message-ID: <350@astroatc.UUCP>
Date: Mon, 6-Jul-87 23:08:43 EDT
Article-I.D.: astroatc.350
Posted: Mon Jul  6 23:08:43 1987
Date-Received: Thu, 9-Jul-87 04:39:32 EDT
References: <8270@amdahl.amdahl.com> <359@rocky2.UUCP> <338@astroatc.UUCP> <1683@umn-cs.UUCP>
Reply-To: johnw@astroatc.UUCP (John F. Wardale)
Organization: Astronautics Technology Cntr, Madison, WI
Lines: 65
Keywords: parrallel computing; performance; vector computing
Summary: New algorithms good, but costly to port!

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Comment on using up MIPS:
a 100 mip or 1gip or 10gip ... workstation *IS* useful, even if
its utilization is 1% .1% or .01% as long as it gives faster
*RESPONCE*  ... Any time you do something, the faster its done,
the better!  

PS:  I said useful, not necessarily cost-effective.

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In article <1683@umn-cs.UUCP> herndon@umn-cs.UUCP (Robert Herndon) writes:
>In article <338@astroatc.UUCP>, I wrote what prompted Robert.

>  Parallelize that, no.  Parallelize the same problem, which presumably
>is "tell me how projectile X under conditions Y will fall", is
>entirely a different question, and may be parallelizable,
>depending on the differential equation involved.  Just as
		...example of... [deleted for brevity]
 Your garden variety scanner is serial, but
a fancy-new algorithm called "a Mealy Machine" is much better.

>  If you mean "ALL" problems, then I'd have to agree with you.
>There certainly are problems that seem to require a serial
>solution strategy.  BUT:  you must differentiate between
>"a problem" and "code to solve a problem".  They are NOT identical,
>and an algorithm change makes it a whole new ball game.

New methods are great for new codes, but given the amount of code
in the world, and the number of new machines comming out, how much 
effort do you REALLY think goes into each conversion ???  I'd have
a LOT more faith in your ideas if you had a parallel "guru"
program that could identfy all your "poor" algorithms and fix them
for you.  (Maybe it could just say stuff like:  xxx looks like a
scanner.  If you convert this, you could get 10:1 improvements,
see file /usr/lib/guru/algorithm-examples/mealy for details.)
(slightly :-)

Programs run on Cray-cost machines can/will/are converted and/or
fixed to run well, but most "users" are more likely to do simple
"ports".  Resatating this idea, If the machine is harder
[arbitrarly comparison] to program, then it will not be accepted
as well (it will have lower sales)

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I think you intentionally chose the "scanner" example so you could
claim that its in the code distributed with the system, and will
therefore be in all the vendor-supplied (system) programs, but
scanning constitues a very *SMALL* fraction of the total CPU time,
so these sort of algorithmic improvements must be applied in a
wholesale manner to all the sub-parts of each program.  That will
(99.9% likely) be VERY expensive!!


			John W

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Name:	John F. Wardale
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