[Trilinos-Users] Best practices for parallel solutions?

[Paul Dionne]

Thanks Mike and Nico.  I'll look into FECrsMatrix and NOX and let you 
know how it goes.  Can you point me to a good NOX example for a 
nonlinear solution of [A]{x}={b}?

On 12/12/2011 4:18 PM, Nico Schlömer wrote:
> 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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>>

-- 
Paul J. Dionne
Technnical Fellow
CFD Research Corporation
215 Wynn Drive, 5th floor
Huntsville, Al  35805
(256) 726-4837
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