[Trilinos-Users] Solvers and preconditioners available for Epetra_VbrMatrices

[Charles Boivin]

Mike,

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

Charles,

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.

Thanks.

Mike


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.
>