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From: rpeglar@eta.ETA.COM (Rob Peglar)
Newsgroups: comp.arch
Subject: Linpack
Message-ID: <8700208@eta.ETA.COM>
Date: Thu, 5-Nov-87 10:17:45 EST
Article-I.D.: eta.8700208
Posted: Thu Nov  5 10:17:45 1987
Date-Received: Mon, 9-Nov-87 06:51:20 EST
Reply-To: rpeglar@eta.UUCP (Rob Peglar)
Distribution: na
Organization: ETA Systems, Inc., St Paul, MN, USA
Lines: 46
Keywords: ETA, supercomputer, Linpack, Cray
Summary: ETA-10P questions answered

A recent posting read as follows:


>  
>  I have seen it many times in the Media.  The 10-P is rated
>  at 375 Mflops, but does Linpack at 25.  Why the big difference?
>  Do other supercomputers behave similarly?  What does a Cray 2
>  do on Linpack?
>  -- 
>  Kevin Buchs   3500 Zycad Dr. Oakdale, MN 55109  (612)779-5548
>  Zycad Corp.   {rutgers,ihnp4,amdahl,umn-cs}!meccts!nis!zycad!kjb


1)  The 10-P rating at 375 Mflops is PEAK rate.  This means long (500
elements, for example) vectors of 32-bit precision running in a linked
triad computation (e.g. A = B*C + D, all vectors).  The quoted example
of Linpack does not perform at peak rates.

2)  Yes, other supercomputers behave similarly, in a loose sense.  The
ETA architecture is sufficiently different than, for example, a Cray X
model.  Their Linpack ratings will be slower than their peak ratings.

3)  What does a Cray-2 do on Linpack?  Dr. Dongarra's report dated
October 30, 1986 (about a year old now) shows the Cray-2 running at
15 Mflops in one processor using CFT2.7, rolled BLAS.  No listing for
coded BLAS.  

*** It must be noted that the published rates on ETA10-P (and all
other models of ETA procesors) are for 100x100 Linpack, 64-bit (full)
precision, all Fortran.  ***  (The Cray-2 number above is the same
calculation)

There exist many articles in the literature which explain the various
supercomputer architectures.  Understanding Linpack results can only be
achieved with study of same.

BTW, the Cray X-MP single processor rates at 24 Mflops, using CFT 1.13,
rolled BLAS.  Remember, these numbers vary with compilers' astuteness.
Using CFT 1.15, for example, may give better numbers.  Try it out.

The ETA10-P rating used the ETA Fortran 77 compiler 1.0.   

Rob Peglar
ETA Systems, Inc.

Disclaimer:  The above is not an opinion of ETA Systems, Inc.  It's the truth.