Re: how to inverse a sparse matrix in Petsc?

[Barry Smith <bsmith@xxxxxxxxxxx>]

On Feb 4, 2008, at 12:20 PM, Yujie wrote:

what is the difference between sequantial and parallel AIJ matrix? Assuming there is a matrix A, if I partitaion this matrix into A1, A2, Ai... An.
A is a parallel AIJ matrix at the whole view, Ai is a sequential AIJ matrix? 

   It is not that simple. Ai is split into two parts 1) the "block diagonal" part and 2) the "off diagonal part" ; this is explained

in the manual page for MatCreateMPIAIJ(). If you want to do operations on the pieces you will need to understand the

code in src/mat/impls/aij/mpi. 

   What do you want to do with Ai? 

I want to operate Ai at each node.
In addition, whether is it possible to get general inverse using MatMatSolve() if the matrix is not square?

 No, that requires much more complicated linear algebra technology then is in PETSc.

   Barry

Thanks a lot.

Regards,
Yujie

On 2/4/08, Barry Smith <bsmith@xxxxxxxxxxx> wrote:

    For sequential AIJ matrices you can fill the B matrix with the
identity and then use
MatMatSolve().

    Note since the inverse of a sparse matrix is dense the B matrix is
a SeqDense matrix.

    Barry

On Feb 4, 2008, at 12:37 AM, Yujie wrote:

> Hi,
> Now, I want to inverse a sparse matrix. I have browsed the manual,
> however, I can't find some information. could you give me some advice?
>
> thanks a lot.
>
> Regards,
> Yujie
>