[petsc-users] ISCreateStride and MatGetSubmatrices

[shu guo]

Hi Jed,

I solve the problem. It seems that that the array to hold the Mat is
not necessary, at least I was not assign this value but it works fine.

The mistake I made is that I forget the ierr using MatGetSubmatrices.
It seems without this error indicator, it won't let me proceed. Thank
you for your help. I will look into the tips on use Petsc in fortran.

Shu

On Tue, Aug 28, 2012 at 12:21 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> On Tue, Aug 28, 2012 at 11:18 AM, shu guo <greatgs2008 at gmail.com> wrote:
>>
>> So I have to define this submatrix and extract is into this pre-set
>> location?
>
>
> No, you have to create an array to hold the Mat objects, e.g.
>
> Mat submats(10)
>
>>
>>
>> On Tue, Aug 28, 2012 at 12:03 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> > On Tue, Aug 28, 2012 at 10:56 AM, shu guo <greatgs2008 at gmail.com> wrote:
>> >>
>> >> Hi All,
>> >>
>> >> I think I made a mistake. It seems it crashes when I call the command
>> >> of MatGetSubMatrices. There is an indication that saying,
>> >>
>> >>  MatGetSubmatrices() is slightly different from C since the
>> >>      Fortran provides the array to hold the submatrix objects,while in
>> >> C
>> >> that
>> >>      array is allocated by the MatGetSubmatrices()
>> >>
>> >> What does this mean? I don't even need this command to extract the
>> >> submatrix?
>> >
>> >
>> > It means that you have to allocate the array to hold the result.
>> >
>> > If this seems cumbersome to you, ask yourself why you chose to write in
>> > Fortran. ;-)
>
>