[Trilinos-Users] slow mv-product with FECrsMatrix
Heroux, Michael A
maherou at sandia.gov
Fri Jan 21 19:33:19 MST 2011
Nico,
Are you using MPI for the parallelism (or OpenMP)? I am assuming MPI.
There are known issue with MPI mapping to multicore nodes. I don't know if
any of these are issues for you.
Can you do other MPI based computations with good speedup? If so, then it
might be something Epetra-specific. Is this something you can confirm?
Thanks.
Mike
On 1/21/11 8:21 PM, "Nico Schlömer" <nico.schloemer at ua.ac.be> wrote:
> Hi all,
>
> I just performed some simple timings for one matrix-vector product with
> an Epetra_FECrsMatrix, distributed over 48 cores of a shared-memory
> machine. After the matrix construction, keoMatrix.GlobalAssemble() is
> called to optimize the storage.
> RangeMap and DomainMap are (about) show that rows and columns are about
> evenly spread over the cores, and when performing the actual mv-product,
>
> M->Apply( *epetra_x, *epetra_b );
>
> epetra_x has the DomainMap and epetra_b has the RangeMap of M.
>
> I expected that the process would take approximately evenly long on each
> for each of the processes, so I was surprised to see
>
> ==============================================================================
> ========
> TimeMonitor Results
>
> Timer Name Min over procs Avg over procs Max
> over procs
> ------------------------------------------------------------------------------
> --------
> Matrix-vector multiplication 0.009653 (1) 0.01869 (1) 0.03121 (1)
> ==============================================================================
> ========
>
> There are cases where T_max/T_min > 5, too.
>
> This of course destroys the parallel efficiency of the mv-products.
>
> Any hint on what may possibly cause this?
>
> Cheers,
> Nico
>
>
> _______________________________________________
> Trilinos-Users mailing list
> Trilinos-Users at software.sandia.gov
> http://software.sandia.gov/mailman/listinfo/trilinos-users
>
More information about the Trilinos-Users
mailing list