Tom Elken wrote:
mathematician but im trying to understand how the benchmark operates.
I would like to test my system by seeing how many FLOPS are achieved
using only the Matrix Multiply.
You could probably download the HPC Challenge benchmark (from
http://icl.cs.utk.edu/hpcc/software/index.html ) and cut-paste some
code from it's DGEMM (Double-precision, GEneral Matrix-Multiply)
sub-benchmark as a relatively easy way to get a test program for
matrix-multiply.
DGEMM is typically ~90% or more of the HPL benchmark's profile.
Indeed I have been doing that for the last couple of years since hpcc appeared.
It is trivial to slightly modify one file of the hpcc source such that you can
run just one or two or the seven contained benchmarks via setting a shell
variable - for example just to run dgemm in your case, or say ptrans or gups in
my case. It is also very easy to pipe the hpcc output though a couple of lines
of perl or sed so as to get just the summary output lines for the subset of
tests that you ran.
As for the flops, this can depend on the lower bits of the matrix size - it is
common to see dgemm implimentations oscilate due to cache line hits and the
like. rather than speak in terms of actual flops, it usuely make more sense to
quote the percentage of theoretical peak you get. The theoretical peak is well
defined - simply the cpu's clock speed mulitplied up by favious factors like:
- times number of cpus per Motherboard
- times number of cores per cpu
- times number of floating point instructions issues per cycle (2 for itanium
and alpha, 1 for xeon/opteron)
- times width of any SIMD unit (2 for the 2*64-bit wide SSE2)
- times two if your FPUs can do chained muladd (like itanium)
- times 75% reduction factor if you can't issue floating point loads fast
enough (was this G5?)
Some cpu architectures come out better than others but you should expect to get
say >85% even on the worst (thank you Mr Goto :-) )
Daniel.
--------------------------------------------------------------
Dr. Dan Kidger, Quadrics Ltd. [EMAIL PROTECTED]
One Bridewell St., Bristol, BS1 2AA, UK 0117 915 5505
----------------------- www.quadrics.com --------------------
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