Questions regarding MatCreateMPIAIJWithArrays

[Mads Fredrik Skoge Hoel]

Thanks, for clearing that up. Truly helps alot. From an efficiency point
of view I will go with option 2. And maybe implement a third option: to
create an SeqAIJ if run as a uniprocessor program.

Regards,
Mads

> 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.
>
>