[petsc-dev] Two questions about PC Object

[Matthew Knepley]

On Mon, Aug 8, 2011 at 2:17 AM, Gabriele Jost <gjost at tacc.utexas.edu> wrote:

>  Hello!
>
>  I am working with a user of XSEDE (forerly know as TeraGrid) on
> converting his code from Scalapack to using PETSc. His physical problem
> yields matrices which are sparse, but the structure is rather general.
> We have a version going that works very well for one type of problems. I
> can use MUMPS or SuperLU and I get results which are pretty close to what he
> gets when using Scalapack.
> However, I am running into problems with the matrices that correspond to a
> different problem type. I get results when using MUMPS, but they differ
> widely from the Scalapack results. With MUMPS I get an error like:
>
>  Error reported by MUMPS in numerical factorization phase: INFO(1)=-1,
> INFO(2)=359
>
>  I noticed that for the matrix types where I get good results, the
> nonzeros reported for the PC Object type exactly the number of entries in my
> input data for the matrix (MPIAIJ format). For the type that does not work,
> petsc reports more nonzeros than what I enter. The message looks like this:
>
>    linear system matrix = precond matrix:
>   Matrix Object:
>     type=mpiaij, rows=123120, cols=123120
>     total: nonzeros=59094408, allocated nonzeros=59173613
>
>  My questions are:
>
>  1) Does anybody know what the error INFO(1)=-1 means in MUMPS?
>

-1 means the error code is in INFO(2). I cannot find any online list of the
error codes. I suggest mailing the MUMPS list.

  Thanks,

     Matt


> 2) How does PETSc calculate the number of nonzeros for the PC matrix?
>
>  Have banging my head against this problem for a while. Any advice is
> highly appreciated.
>
>  Many thanks in advance!
>
>  Gabriele Jost
> Texas Advanced Computing Center
>
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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