how to inverse a sparse matrix in Petsc?

Ben Tay zonexo at gmail.com
Tue Feb 5 07:57:51 CST 2008

```Hi everyone,

I was reading about the topic abt inversing a sparse matrix. I have to
solve a poisson eqn for my CFD code. Usually, I form a system of linear
eqns and solve Ax=b. The "A" is always the same and only the "b" changes
every timestep. Does it mean that if I'm able to get the inverse matrix
A^(-1), in order to get x at every timestep, I only need to do a simple
matrix multiplication ie x=A^(-1)*b ?

Hi Timothy, if the above is true, can you email me your Fortran code
template? I'm also programming in fortran 90. Thank you very much

Regards.

Timothy Stitt wrote:
> Yes Yujie, I was able to put together a parallel code to invert a
> large sparse matrix with the help of the PETSc developers. If you need
> any help or maybe a Fortran code template just let me know.
>
> Best,
>
> Tim.
>
>> Hi
>> There was a discussion between Tim Stitt and petsc developers about
>> matrix inversion, and it was really helpful. That was in last Nov.
>> You can check the emails archive
>>
>>
>>
>>
>> */Yujie <recrusader at gmail.com>/* 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? 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? Thanks a lot.
>>
>>     Regards,
>>     Yujie
>>
>>
>>     On 2/4/08, *Barry Smith* <bsmith at mcs.anl.gov
>>     <mailto:bsmith at mcs.anl.gov>> 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
>>         >
>>         > thanks a lot.
>>         >
>>         > Regards,
>>         > Yujie
>>         >
>>
>>
>>
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>
>
>

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