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
