[petsc-users] CPU-scaling

[Torquil Macdonald Sørensen]

It is a standard eigenvalue problem, and I'm only using default algorithm
options, so I don't think I'm using any nontrivial spectral transformation.

The program is just ex1.c from the documentation, available here:

http://www.grycap.upv.es/slepc/documentation/current/src/eps/examples/tutorials/ex1.c

FAQ #6 mentions MUMPS, which I don't have the moment, so I'll have to look
into that.

- Torquil



On 18 October 2013 16:46, Jose E. Roman <jroman at dsic.upv.es> wrote:

>
> El 18/10/2013, a las 16:42, Torquil Macdonald Sørensen escribió:
>
> > Hi!
> >
> > I'm just starting to use SLEPc on a quad-core workstation computer
> (Intel Core i5-2500 CPU @ 3.30GHz).
> >
> > But I'm not getting the speedup that I was expecting, when increasing
> the number of cores. E.g. when running ex1.c from the documentation, on 1,
> 2, 3 and 4 cores. When asking for the 500 eigenvalues of smallest
> magnitude, for a 5000x5000 matrix, I'm getting the following approximate
> timings:
> >
> > # n_core  time_usage
> > 1              480s
> > 2              400s
> > 3              500s
> > 4              580s
> >
> > Should I not expect a speedup for n_core > 2?
> >
> > The example is using the krylovschur algorithm. For all four runs, the
> program states "Number of iterations of the method: 33".
> >
> > I'm using PETSc 3.4.3, SLEPc 3.4.3, OpenMPI 1.6.5, and everything is
> compiled using GCC 4.8.1 or 4.8.2.
> >
> > Best regards
> > Torquil Sørensen
> >
>
> Is it a generalized eigenproblem and/or are you doing shift-and-invert? In
> that case, have a look at FAQ #6
> http://www.grycap.upv.es/slepc/documentation/faq.htm
>
> Jose
>
>
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