[Trilinos-Users] Epetra_CrsMatrix and AztecOO

[Mike Heroux]

Bora,

What you are running into is some of the legacy design issues of Aztec, a
Krylov solver package developed quite some time ago that provides the core
functionality of AztecOO.  Aztec was designed with PDE-related matrices in
mind.  As a result, in some places it assumes that the user matrix is both
square and has a diagonal.  If your matrix is rectangular or has does not
provide all diagonal values (even if they are zero), then some computation
and communication primitives can fail, as you have seen.

Epetra does not have these restrictions.  It is completely general in its
support of matrix patterns and distribution.  However, since AztecOO uses
Epetra in conjunction with the underlying Aztec package, your use of Epetra
is restricted when used with AztecOO.

Mike 

> -----Original Message-----
> From: trilinos-users-bounces at software.sandia.gov 
> [mailto:trilinos-users-bounces at software.sandia.gov] On Behalf 
> Of Bora Ucar
> Sent: Saturday, November 05, 2005 5:24 PM
> To: trilinos-users at software.sandia.gov
> Subject: [Trilinos-Users] Epetra_CrsMatrix and AztecOO
> 
> Hi,
> 
> I had a problem in using a Epetra_CrsMatrix to define a 
> linear problem and solving the problem with AztecOO, e.g., 
> with programs similar to
> ---------------
>  Epetra_CrsMatrix A(Copy, Map, numNz);
> // fill the matrix
>  Epetra_Vector x(Map);
>  Epetra_Vector b(Map);
>  //initialize b
>   Epetra_LinearProblem Problem(&A,&x,&b);
>   AztecOO Solver(Problem);
>   ...
>   Solver.Iterate(..,..);
> ---------------
> I got the following error
> 
> AZ_extract_comm_info: Received elements must be stored after
>                    all XXX local elements
> 
> and then figured out that AztecOO requires a zero free 
> diagonal. I added diagonal entries to A and then the solution 
> followed smoothly.
> 
> What about Multiply member function(s) of the Epetra_CrsMatrix class?
> Do I have to specify diagonal entries for these functions to 
> compute correctly?
> 
> Thank you,
> 
> Bora
> 
> 
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