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

[Zhang, Hong]

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<mailto: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<mailto: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

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