[petsc-users] PetscLogFlop for a sqrt()

Justin Chang jychang48 at gmail.com
Tue Apr 21 12:23:37 CDT 2015

Last question

I would like to report the efficiency of my code. That is, flops/s over the
theoretical peak performance (on n-cores). Where the TPP is clock *
FLOPS/cycle * n. My current machine is a Intel® Core™ i7-4790 CPU @ 3.60GHz
and I am assuming that the FLOPS/cycle is 4.

One of my serial test runs has achieved a FLOPS/s of 2.01e+09, which
translates to an efficiency of almost 14%. I know these are crude
measurements but would these manual flop counts be appropriate for this
kind of measurement? Or would hardware counts from PAPI?


On Tue, Apr 21, 2015 at 11:16 AM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
> > Flop is Floating Point Operation. The index calculation is an Integer
> > Operation. I agree that we could probably start counting
> > those as well since in some sorts of applications its important, but
> right
> > now we don't.
> Index calculations often satisfy recurrences that the compiler folds
> into pointer increments and the like.  Also, some architectures, like
> PowerPC, have floating point instructions that include mutating index
> operations in the true spirit of RISC. ;-)
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