[petsc-users] CPU-scaling

[Jose E. Roman]

No, you don't need MUMPS for ex1.c with default options.
Then I don't know what is happening. Did you build PETSc --with-debugging=0 ? You should send performance data obtained with -log_summary, otherwise we cannot guess what happens.

Jose


El 18/10/2013, a las 17:21, Torquil Macdonald Sørensen escribió:

> 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
> 
>