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

[Fande Kong]

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 <http://user.coarse.mx> = 20; user.coarse.my
<http://user.coarse.my> = 20; user.coarse.mz <http://user.coarse.mz> = 20;*

*  ierr = PetscOptionsGetInt(NULL,NULL,"-Mx",&user.coarse.mx
<http://user.coarse.mx>,NULL);CHKERRQ(ierr);*
*  ierr = PetscOptionsGetInt(NULL,NULL,"-My",&user.coarse.my
<http://user.coarse.my>,NULL);CHKERRQ(ierr);*
*  ierr = PetscOptionsGetInt(NULL,NULL,"-Mz",&user.coarse.mz
<http://user.coarse.mz>,NULL);CHKERRQ(ierr);*
*  ierr =
PetscOptionsGetInt(NULL,NULL,"-ratio",&user.ratio,NULL);CHKERRQ(ierr);*

*  if (user.coarse.mz <http://user.coarse.mz>) Test_3D = PETSC_TRUE;*

*  user.fine.mx <http://user.fine.mx> = user.ratio*(user.coarse.mx-1)+1;*
*  user.fine.my <http://user.fine.my> = user.ratio*(user.coarse.my-1)+1;*
*  user.fine.mz <http://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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