[petsc-users] CPU-scaling

[Jose E. Roman]

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