Thanks Wolfgang,
Unfortunately I cannot use MPI. It should be strictly a host-only code with
no networking at all, so I am using threads. I could use fully blown
processes, of course, but it's an overkill.
Cheers,
Franco
On Monday, June 17, 2019 at 6:30:14 PM UTC+2, Wolfgang Bangerth wrote:
>
> On 6/17/19 6:10 AM, Franco Milicchio wrote:
> >
> > we're about to implement an eigenvalue problem that needs multiple
> solutions.
> > In particular, we're going to compute min & max eigenvalues of several
> > matrices, so we were going to spawn some threads and solve some in
> parallel.
> >
> > The problem is that, as far as I see, there are wrappers in deal.II for
> SLEPc,
> > so PETSc, but we cannot use MPI in our system. PETSc works only with
> MPI, and
> > I cannot start multiple threads, or at least that is what I understand
> (see
> > https://www.mcs.anl.gov/petsc/miscellaneous/petscthreads.html).
>
> I think that is only partially true. What is *not* safe is to let PETSc
> access
> the same data structures from multiple threads. That includes an MPI
> communicator.
>
> But if you are willing to duplicate the matrix and use different (cloned)
> MPI
> communicators for the copies of the matrix, then I suspect that you can
> use
> PETSc on multiple threads as long as every thread accesses only one of the
> matrices and a unique MPI communicator.
>
> That said, if you're already using MPI, why not just put one MPI process
> on
> each processor core? In that case, you don't need multithreading.
>
> Best
> W.
>
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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