[Trilinos-Users] Solvers and preconditioners available for Epetra_VbrMatrices

Charles Boivin charles.boivin at mayahtt.com
Fri Sep 16 11:13:38 MDT 2011


Ok, thanks for the answer. We also use Ifpack occasionally. So I guess my question remains: how would I know I have a problem? Does it not compile? Not run properly?

I am also asking because I just tried quickly to wrap my matrix into an Epetra_VbrRowMatrix container before passing it to the (ML) preconditioner and I get a very different behavior than if I don't do that. Is that expected? What do you mean exactly when you say that all preconditioner will be constructed as point-entry objects?

Thanks in advance for your time,

Charles Boivin 

-----Original Message-----
From: Heroux, Michael A [mailto:maherou at sandia.gov] 
Sent: Friday, September 16, 2011 12:07 PM
To: Charles Boivin; trilinos-users at software.sandia.gov
Subject: Re: [Trilinos-Users] Solvers and preconditioners available for Epetra_VbrMatrices


If it is working for you, then don't worry.  The problems tend to happen
with Ifpack since certain preconditioner options use more methods from the
RowMatrix interface.



On 9/16/11 11:02 AM, "Charles Boivin" <charles.boivin at mayahtt.com> wrote:

> Mike,
> This last comment regarding preconditioners is puzzling me a bit. We've
> recently started using an Epetra_VbrMatrix (actually Epetra_FEVbrMatrix) in
> our code, and are feeding it to the ML preconditioner. Now, from what you are
> saying, this should not be working...
> How does that manifest itself exactly? Would it crash? Give the wrong answer?
> Or simply not be as efficient as it should?
> We've been able to get answers out of this setup...
> Thank you,
> Charles Boivin
> -----Original Message-----
> From: trilinos-users-bounces at software.sandia.gov
> [mailto:trilinos-users-bounces at software.sandia.gov] On Behalf Of Heroux,
> Michael A
> Sent: Thursday, September 15, 2011 3:04 PM
> To: Alberto F. Martín-Huertas; trilinos-users at software.sandia.gov
> Cc: Javier Principe
> Subject: Re: [Trilinos-Users] Solvers and preconditioners available for
> Epetra_VbrMatrices
> Alberto,
> All of the solvers and preconditioners in Trilinos are usable with
> Epetra_VbrMatrix objects.
> The iterative solvers will use your VbrMatrix directly and utilize the block
> structure.
> However, there are no block entry preconditioners.  All of the
> preconditioners will be constructed as point entry objects.  In fact,
> because of a structural deficiency in Epetra_VbrMatrix, you will need to
> construct an Epetra_VbrRowMatrix object (which is a light-weight wrapper
> around Epetra_VbrMatrix) and pass that to the preconditioner.  It's a single
> line of code, but is required for proper interpretation of the
> Epetra_RowMatrix interface with a VbrMatrix object.
> I hope this helps.
> Mike
> On 9/15/11 1:04 PM, "Alberto F. Martín-Huertas" <amartin at cimne.upc.edu>
> wrote:
>>  Dear Trilinos-Users,
>  is there any reference where I can
>  find which krylov
>> subspace solvers (AztecOO)
>  and preconditioners (ML, Ifpack, AztecOO) are
>> available
>  for variable block row distributed matrices
>  (i.e.,
>> EpetraVbrMatrix).
>  Thanks in advance.
>  Best regards,
>   Alberto.

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