[Trilinos-Users] Problem with AztecOO constructor before or after A.FillComplete()

Heroux, Michael A maherou at sandia.gov
Tue Jul 30 12:58:42 MDT 2013


Luca,

This is a restriction in the AztecOO data model.  On each processor
AztecOO needs to have columns indices exactly match the row indices.
Additional column indices due to off-processor needs must be ordered last
and grouped together by MPI rank.  Epetra usually does the ordering
automatically for you, as long as you don¹t specify the column map when
calling the Epetra_CrsMatrix constructor.  If you are specifying the
column map, or providing your own operator then you need to make sure that
the column indices are ordered this way.

If you are using the typical Epetra_CrsMatrix constructors, you probably
have a column on some processor that has no entries on a processor that
owns the corresponding row, and therefore that column ID is missing and
making AztecOO complain.  Often this is an error in the logic that
generates matrix coefficient.

Mike


On 7/30/13 10:19 AM, "Luca Heltai" <luca.heltai at gmail.com> wrote:

>Dear All, 
>
>we are having some problems on a simple program that solves a linear
>system in parallel using AztecOO. Our program was modified from one of
>the examples, only to fill the matrix with "interesting" values, and it
>works fine in serial.
>
>When running it in parallel, we get the following cryptic message:
>
>
>AZ_extract_comm_info: Received elements must be stored after
>                   all 726 local elements
>
>
>If the AztecOO solver is initialized *before* the call to FillComplete
>for the matrix, then the problem goes away. That is:
>
>
>A.FillComplete();
>AztecOO Solver(&A, &x, &b);  // Crashes
>
>====
>
>AztecOO Solver(&A, &x, &b);  // Works
>A.FillComplete();
>
>
>Since our goal is to solve a Komplex_LinearProblem, we need to
>FillComplete before defining the Linear Problem, and therefore the
>Solver... 
>
>We have not been able to reproduce the error on the example, so we guess
>there must be something wrong with our code...
>
>Any idea on what the error above means?
>
>Thanks, 
>
>Luca & Ivan.
>
>--
>Luca Heltai <luca.heltai at gmail.com>
>http://people.sissa.it/~heltai/
>Scuola Internazionale Superiore di Studi Avanzati
>Phone:  +39 040 3787 449, Office: 622
>--
>There are no answers, only cross references
>
>
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