[petsc-users] Obtaining bytes per second

[Matthew Knepley]

On Wed, May 6, 2015 at 8:29 AM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
> > I think the idea is to be explicit. I would just use something like
> >
> >   # Vecs * Vec size * 8 bytes/double + <same for Mat>
> >
> > and forget about small stuff. This model is uncached,
>
> This is for a perfect cache model -- each byte of the data structures
> needs to be fetched from DRAM only once.
>

I meant uncached, in which you count # Vecs for any operation you are
doing. If you count # Vecs for the whole program, then you have perfect
cache.

  Matt


> Make sure that "# Vecs" actually means the number that are accessed.
> For example, GMRES accesses an increasing number of vectors on each
> iteration (until a restart).
>
> > and you just state that up front. Someone else can take the data and
> > produce a more nuanced model.
> >
> > You can use the Flop counts (not Flop/s) from PETSc,  and get a rough
> > estimate
> > of flop/byte ratio.
>
>


-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150506/ed3ff1c1/attachment.html>