[Trilinos-Users] Best practices for parallel solutions?

[Paul Dionne]

Also, what is the best way to get the ghost cell values after solving.  
After the parallel solution I have a solution vector {x} defined on a 
non-overlapping map.  I would like to get a vector {y} that contains the 
solution in the ghost cells as well as the real cells.  Thus, the target 
map would be an overlapping map, but if I understand the Export function 
correctly I cannot export to an overlapping map - is that correct?

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.
>>
>>
>> _______________________________________________
>> Trilinos-Users mailing list
>> Trilinos-Users at software.sandia.gov
>> http://software.sandia.gov/mailman/listinfo/trilinos-users
>>

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

Confidentiality Notice

The information contained in this communication and its attachments is intended only for the use of the individual to whom it is addressed and may contain information that is legally privileged, confidential, or exempt from disclosure. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution, copying, or reliance on this communication is strictly prohibited. If you have received this communication in error, please notify confidentiality at cfdrc.com (256-726-4800) and delete the communication without retaining any copies.