[Trilinos-Users] Omitting Row/Columns from matrices

Heroux, Michael A maherou at sandia.gov
Thu Jul 3 08:03:51 MDT 2008


I can think of several ways to remove Dirichlet boundary conditions.  Two of them are:

1) The simplest way is to keep them in the system, set the diagonal value to 1, all other matrix values to zero, and the RHS value to the BC value.

2) Use the CrsSingletonFilter class which automatically detects and removes rows and columns that have only a single value, producing a reduced system.  Dirichlet BCs are a one of the cases this class addresses.  There are two versions of this class: One in Epetra that can be used directly, another in EpetraExt that can be used as part of the Transform framework.


On 7/3/08 2:06 AM, "Davood Ansari" <david.ansari at gmail.com> wrote:

Hi all

I am imposing boundary conditions on a FE eigen-problem. Ax = lambda B x
>From time to time I need to impose different BCs and in eigen problems
the best way to is to omit the rows and columns associated with boundary related
DOF from both RHS and LHS matrices (as if these rows and columns never existed).
This is, however, different from forcing the rows and columns to all zeros.
Wanted to know if there is an efficient (or even not very efficient) way of doing it.


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