NAS Parallel Benchmarks for Current Hardware
egan at sense.net
Mon Jun 16 12:02:49 EDT 2003
Unfortunately benchmarking is a game. I tell my customers to benchmark
their application. It is the only way to really know what will work best
for any particular application. We offer a benchmark lab to assist with
> -----Original Message-----
> From: andy at ideafix.litec.csic.es [mailto:andy at ideafix.litec.csic.es]
> Sent: Monday, June 16, 2003 2:45 AM
> To: egan at sense.net; beowulf at beowulf.org
> Subject: Re: NAS Parallel Benchmarks for Current Hardware
> Egan Ford wrote:
> > > Unfortunately, I am not sure linpack and spec reliably
> measure what is
> > > important for numerical work on a beowulf.
> > I disagree.
> I admit I should have been more careful and inserted the word "our"
> befor "numerical work on beowulf". My concern is partly that they does
> not test what I want to know and partly that linpack and spec blob
> ratings shift a lot of hardware.
> What I need (and I supect many others but I will not speak
> for them this
> time) is:
> * a range of grid sizes so that I can see cache/memory effects
> * a range of common numercal solvers (covering most of those
> I use) with
> differing communication characteristics so that I can gauge the likely
> behaviour of a range of simulations.
> No single number can provide such information but something
> the like NAS
> parallel benchmarks do.
> 15-20 years ago linpack stopped being a measure of anything
> useful when
> manufacturers adapted their compilers/hardware to generate
> unrepresentatively large blob ratings. This was brought home when
> commissioning a small shared memory machine and we could not get near
> the quoted linpack blob rating using various combinations of
> optimisation flags (just over 10 blobs instead of nearly 30 blobs if I
> recall correctly). After a phone call we used the
> undocumented -linpack
> compiler flag and bingo.
> Evidence is growing that the spec blob ratings have suffered in a
> similar way (though to a lesser degree). See, for example, "Sun breaks
> another SPEC benchmark" in comp.benchmarks:
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