[Trilinos-Users] Best practices for parallel solutions?

[Nico Schlömer]

Hi Paul,

for solving nonlinear problems, you might want to take a look at the
NOX package as well. You specify the linear (Jacobian) operator once
(e.g., as an Epetra_FECrsMatrix as suggested by Mike), and NOX will
take care of all the rest. -- No need for you to think about whether a
copy would be efficient or not.

--Nico




On Mon, Dec 12, 2011 at 9:56 PM, Paul Dionne <pjd at cfdrc.com> wrote:
> I'd like to know the recommended practice for solving parallel linear systems.  I have an implicit finite-volume solver and thus I have ghost cell links during assembly.  I found a presentation entitled "HerouxEpetraConcepts.pptx" that suggested using an assembly map and a solver map.  After assembly, the following commands were given in the presentation:
>
> Epetra_Export Exporter(AssemblyMap, SolverMap);
> Epetra_CrsMatrix SolverMatrix(Copy, SolverMap, 0);
> SolverMatrix.Export(AssemblyMatrix, Exporter, Add);
> SolverMatrix.FillComplete();
>
> My problems are nonlinear so I solve the linear system several times each time step.  Thus, I was wondering about the efficiency and memory requirements of having 2 matrices and performing this matrix copy each time I solve.
>
> Is this the current recommended practice?
>
> I'd also like to know how best to get the ghost cell values after the solution (without doing it myself through MPI).  I'm trying to get it to work using Epetra_Export but not having much luck.
>
> Thanks for any assistance.
>
>
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