[petsc-users] ISCreateStride and MatGetSubmatrices

[Jed Brown]

On Tue, Aug 28, 2012 at 10:42 AM, shu guo <greatgs2008 at gmail.com> wrote:

> Hi Jed,
>
> I was thinking about this issue either. But when I create the matrix,
> I hardcoded as
>
>           call MatCreateMPIBAIJ  (PETSC_COMM_WORLD,4,32,32,
>      &                          PETSC_DETERMINE, PETSC_DETERMINE,
>      &                          PETSC_NULL_INTEGER, mr(np(246)),
>      &                          PETSC_NULL_INTEGER, mr(np(247)),
>      &                          Kmatem, ierr)
>
> And it works good. Does that mean this should not be a concern as you
> mentioned?
>

Probably, but it's still bad practice when using Fortran, and it will cause
problems if you change the integer size later (e.g. to solve problems with
more than 2B degrees of freedom). What does Valgrind say?


>
> Thanks.
>
> Shu
>
>
>
> On Tue, Aug 28, 2012 at 11:37 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> > On Tue, Aug 28, 2012 at 10:33 AM, shu guo <greatgs2008 at gmail.com> wrote:
> >>
> >> Dear All,
> >>
> >> I want to extract a sequential matrix from a MPIBAIJ matrix A with a
> >> dimension of 4n*4n. After assembly A, I use ISCreateStride to define
> >> the index by
> >>
> >>           call ISCreateStride(PETSC_COMM_WORLD,n,0,1,isrow,ierr)
> >
> >
> > Fortran does not do type conversion without interfaces (which are about
> as
> > much hassle as benefit). If you configured PETSc with non-default integer
> > sizes, be sure to declare PetscInt zero,one instead of using numeric
> > literals.
> >
> > Otherwise, run in valgrind to check that there isn't earlier corruption
> and
> > run in a debugger to get a stack trace.
> >
> >>
> >>
> >> And extract the matrix as
> >>           call MatGetSubMatrices(Kmatem,1,isrow,isrow,
> >>      &                           MAT_INITIAL_MATRIX,Kmatemseq)
> >>
> >> But it gives me a segmentation fault when I call ISCreateStride. Is
> >> there anything I did wrong? Thanks for any advice.
> >>
> >> Shu
> >
> >
>
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