[petsc-users] Computing part of the inverse of a large matrix

[Jan Grießer]

Is the MatMumpsGetInverse also wrapped to the python version in PETSc4py ?
If yes is there any example for using it ?
My other question is related to the LU factoriation (
https://www.mcs.anl.gov/petsc/documentation/faq.html#invertmatrix).
Is the LU factorization only possible for sequential Aij matrices ? I read
in the docs that this is the case for ordering.
After setting up my matrix A, B and x i tried:
 r, c = dynamical_matrix_nn.getOrdering("nd")
 fac_dyn_matrix = dynamical_matrix_nn.factorLU(r,c)

resulting in an error:
[0] No support for this operation for this object type
[0] Mat type mpiaij

Am Fr., 27. Sept. 2019 um 16:26 Uhr schrieb Zhang, Hong <hzhang at mcs.anl.gov
>:

> See ~petsc/src/mat/examples/tests/ex214.c on how to compute selected
> entries of inv(A) using mumps.
> Hong
>
> On Fri, Sep 27, 2019 at 8:04 AM Smith, Barry F. via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>>
>> MatMumpsGetInverse() maybe useful. Also simply using MatMatSolve() with
>> the first 1000 columns of the identity and "throwing away" the part you
>> don't need may be most effective.
>>
>>    Barry
>>
>>
>>
>> > On Sep 27, 2019, at 3:34 AM, Jan Grießer via petsc-users <
>> petsc-users at mcs.anl.gov> wrote:
>> >
>> > Hi all,
>> > i am using petsc4py. I am dealing with rather large sparse matrices up
>> to 600kx600k and i am interested in calculating a part of the inverse of
>> the matrix(I know it will be a dense matrix). Due to the nature of my
>> problem, I am only interested in approximately the first 1000 rows and 1000
>> columns (i.e. a large block in the upper left ofthe matrix).  Before I
>> start to play around now, I wanted to ask if there is a clever way to
>> tackle this kind of problem in PETSc in principle. For any input I would be
>> very grateful!
>> > Greetings Jan
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20190930/252ec446/attachment.html>