Newsgroups: sci.physics.plasma
From johncobb@uts.cc.utexas.edu Thu Jan 5 19:28:56 1995
From: johncobb@uts.cc.utexas.edu (John W. Cobb)
Organization: The University of Texas at Austin; Austin, Texas
Subject: Re: speed of cray vs unix work stations

In article <3egvao$ji0@mojo.eng.umd.edu>,
Wayne Hayes <wayne@cs.toronto.edu> wrote:
>johncobb@uts.cc.utexas.edu (John W. Cobb) writes:

Cobb:
Of course any answer depends on your particular code, etc. But in my
experience, the correct number is 10 or less...

Hayes:
Yup, it certainly depends on the specific code. I'm using a Fujitsu
VPX/240, which is a vector supercomputer

On code which is 100% vectorizable (a simple little benchmark I wrote),
it is about 1000 times faster than a Sun SPARCstation IPC, or about 70
times faster than the top-of-the-line SPARC at U of Toronto (I think
it's an SS10/5---something, v8 sparc, 256MB RAM).

Anyway, I'd expect that on highly
vectorizable code, a speedup of 50 is about right. But not all code is
^^^^^^^^^^^^
highly vectorizable, though. Code that I recently wrote with 90%
vectorization ran about 10 times faster on the VPX than on said
high-end SPARC. If the vectorization of your code is less than about
90%, it's probably not worth running on a vector supercomputer.

Cobb again:
I agree. In my last note I didn't say it, but the code I used was
only about 85% vectorizable. So those numbers seem to jive with what
Wayne is saying. Sorry for the omission.

- -
John W. Cobb 16% of all Perot voters believe that if Dolphins
are so smart, they should be able to get out of
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