[petsc-users] Obtaining bytes per second

[Justin Chang]

So to summarize, if I understand everything, I should do the following:

1) calculate the flop/byte ratio for various problem sizes and solver
methods on one process and:

a) use the ratio to estimate the ideal flops/s based on the stream bw.
Compare this to the measured flops/s from my Petsc program?

b) show the associated wall-clock times.

c) warn that this model is uncached and merely gives a rough estimate of
the performance.

2) Do a strong-scaling/speed up study to illustrate how these problems
scale across multiple processes. Optionally see what the optimal number of
processes is required for various problem sizes and solvers.

Am I missing anything?

Thanks,
Justin

On Thursday, May 7, 2015, Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, May 7, 2015 at 8:35 AM, Jed Brown <jed at jedbrown.org> wrote:
>
>> Matthew Knepley <knepley at gmail.com> writes:
>> > I think it would be much more interesting, and no more work to
>> >
>> >   a) Model the flop/byte \beta ratio simply
>> >
>> >   b) Report how close you get to the max performance given \beta on your
>> > machine
>>
>> This is also easily gamed; just use high-memory data structures, extra
>> STREAM copies, etc.
>>
>
> I completely agree that all the performance measures can be gamed, which
> is why
> its important to always show time to solution as well.
>
>    Matt
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
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