Questions regarding MatCreateMPIAIJWithArrays

[Matthew Knepley]

On 4/24/07, Mads Fredrik Skoge Hoel <mfhoel at ifi.uio.no> wrote:
> Thank you for your answer. I did not at first understand Barrys
> suggestion, but looking at it a second time helped.
>
> So if i got it right there is two options:
>
> 1. Barrys suggestion: use code that distributes a SeqAIJ matrix owned by a
> single process to multiple processes. Ie. code from
> http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-dev/src/ksp/pc/impls/openmp/openmp.c.html#PCOPENMP
>
> 2. Randys suggestion: create an empty distributed MPIAIJ matrix, using
> MatCreateMPIAIJ. Have it filled with existing data, distributed or non-
> distributed, in an CRS format, and have it assembeled.

Yes, although you really want the data "distributed" for option 2. If
you are reading
from disk, have all procs read and just ignore rows which you do not own.

  Matt

> Regards,
> Mads
>
>
> > On 4/24/07, Mads Fredrik Skoge Hoel <mfhoel at ifi.uio.no> wrote:
> >> Hi,
> >>
> >> I am in a similar situation as Tim. I am starting out with a sequential
> >> program using PETSc as a solver and this other library to discretisize.
> >> Which hopefully will become a parallel program once run under mpirun.
> >>
> >> But calling MatCreateMPIAIJWithArrays i get the error message:
> >> [0]PETSC ERROR: --------------------- Error Message
> >> ------------------------------------
> >> [0]PETSC ERROR: Object is in wrong state!
> >> [0]PETSC ERROR: Must call MatSetSizes() first!
> >> [0]PETSC ERROR:
> >> ------------------------------------------------------------------------
> >>
> >> This is the call generating the error message:
> >> MatCreateMPIAIJWithArrays(PETSC_COMM_WORLD, n, m, n, m, irow, jcol,
> >> &dpA(1), &A);
> >>
> >> I am probably using the MatCreateMPIAIJWithArrays function wrong or in a
> >> wrong context.
> >>
> >> Is it allowed to call MatCreateMPIAIJWithArrays when running as a
> >> uniprocessor application? Or must I use in a multiprocessor context
> >> calling MatCreateSeqAIJWithArrays on each processor? And how would a
> >> PETSc
> >> solver know that local Mat A is part of a global matrix?
> >
> > No, this method is for people who already have partitioned their matrix.
> > For a
> > uniprocessor application, please follow Barry's instructions for the
> > OPENMP PC.
> > Otherwise, you will need to rework your code as Randy pointed out before.
> >
> >   Thanks,
> >
> >      Matt
> >
> >> Any help is highly appreciated.
> >>
> >> Regards,
> >> Mads
> >>
> >>
> >
> >
> > --
> > The government saving money is like me spilling beer. It happens, but
> > never on purpose.
> >
> >
>
>
>


-- 
The government saving money is like me spilling beer. It happens, but
never on purpose.