[petsc-users] How to use other matrix directly in petsc?

[Bao Kai]

Dear Hong and Matthew,

I looked at the interface file for umfpack, while I did not understand all
the things inside very clearly.   I just began to read petsc manual three
days ago.

I guess the interface file is used to call the functions in umfpack to
solve the linear system.  But the default matrix format in umfack should be
csc, and I did get how the interface handle this problem.


My matrix conversion problem is generally solved. The crucial point is that
you need to count the number of the non-zero entries in each row and use
that information to do the preallocation.

I go forward to try some linear solvers now.

The matrix generated with my problem is a little poor, resulting from a
mixed finite element method, asymmetric and indefinite. And the inclusion
of irregular boundary makes it worse.  This is actually one reason I began
with a direct solver.

If you have any suggestions on solve this kinds of linear systems, please
tell me.

Thank you very much.

Best Regard,
Kai



> Message: 3
> Date: Wed, 9 Nov 2011 08:44:24 -0600
> From: Hong Zhang <hzhang at mcs.anl.gov>
> Subject: Re: [petsc-users] How to use other matrix directly in petsc?
> To: PETSc users list <petsc-users at mcs.anl.gov>
> Message-ID:
>        <CAGCphBsnmj0uvTnvcWvg=TCBiNhzuiBF8CAw1p3uKZjiyE7ySw at mail.gmail.com
> >
> Content-Type: text/plain; charset=ISO-8859-1
>
> Bao:
> You may look at petsc-umfpack interface
> ~petsc/src/mat/impls/aij/seq/umfpack/umfpack.c
>
> It seems umfpack use csr format, same as petsc aij format.
>
> Hong
>
> > Dear all,
> > I have been writing a serial FEM code with a direct linear solver
> umfpack,
> > which is pretty easy to use. The problem is the memory required turned
> to be
> > very big and I can not afford it.
> > So I want to turn to PETSC to use ?some iterative solver.
> > I have written the the whole matrix assembly process with?coordinates
> list
> > format. The matrix can be converted to CSC format to use umfpack.
> > When I tried to use MatSetValues to generate the Matrix for petsc, it
> turned
> > out to be really slow.
> > I am wondering if there is some?efficient?way to convert the generated
> > matrix ( with COO, or CSC, or even CSR ) properly to make it usable for
> > PETSC.
> > Since the code at the moment is serial, the methods working for serial
> petsc
> > will be OK.
> > And I do many matrix manipulation( some may not easy with petsc) during
> the
> > matrix assembly, so I do not want to rewrite the whole assembling process
> > with petsc at the moment.
> > I just want to convert the matrix generated to the format the petsc can
> use.
> > It can save much time.
> > Thank you very much.
> >
> > Best Regards,
> > Kai
> >
> >
> >
>
>
>
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