[petsc-users] Processor's coarse DMDA must lie over fine DMDA ( i_start 1375 i_c 687 i_start_ghost_c 689)

[Fande Kong]

OK, I figured it out. It was caused by the different partition of the
coarse DA from the fine DA.

I will fix ex96.c.

Thanks,

Fande,

On Sat, May 11, 2019 at 7:24 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
>    Check the source code for exact details.
>
>
> > On May 11, 2019, at 5:58 PM, Fande Kong via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
> >
> > Hi All,
> >
> > I was running src/mat/examples/tests/ex96.c  with "-Mx 1000 -My 1000 -Mz
> 1000"  with 8192 MPI ranks, and got the message.  If I changed the mesh
> size a little bit (such as -Mx 400 -My 400 -Mz 400), then the code ran
> fine.
> >
> > The relationship between the coarse mesh and the fine mesh is defined
> through the following code
> >
> >
> >   user.ratio     = 2;
> >   user.coarse.mx = 20; user.coarse.my = 20; user.coarse.mz = 20;
> >
> >   ierr = PetscOptionsGetInt(NULL,NULL,"-Mx",&user.coarse.mx
> ,NULL);CHKERRQ(ierr);
> >   ierr = PetscOptionsGetInt(NULL,NULL,"-My",&user.coarse.my
> ,NULL);CHKERRQ(ierr);
> >   ierr = PetscOptionsGetInt(NULL,NULL,"-Mz",&user.coarse.mz
> ,NULL);CHKERRQ(ierr);
> >   ierr =
> PetscOptionsGetInt(NULL,NULL,"-ratio",&user.ratio,NULL);CHKERRQ(ierr);
> >
> >   if (user.coarse.mz) Test_3D = PETSC_TRUE;
> >
> >   user.fine.mx = user.ratio*(user.coarse.mx-1)+1;
> >   user.fine.my = user.ratio*(user.coarse.my-1)+1;
> >   user.fine.mz = user.ratio*(user.coarse.mz-1)+1;
> >
> >
> > I was wondering what is the rule to determine what sizes I could pass
> in?
> >
> > Thanks,
> >
> > Fande,
>
>
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