[petsc-users] Matrix Partitioning using PARMETIS

[Smith, Barry F.]

   Yes, by default there is one subdomain per process so if you run on one process you will get all zero indices. Run on two processes and you should see a partitioning.  See also MatPartitioningSetNParts()

   Barry


> On Mar 12, 2019, at 3:03 AM, Eda Oktay via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hello,
> 
> I have a Laplacian matrix PL of matrix A and I try to partition A using PARMETIS. Since PL is sequential and not adjacency matrix, I converted PL to AL, then write the following code:
> 
>   ierr = MatConvert(PL,MATMPIADJ,MAT_INITIAL_MATRIX,&AL);CHKERRQ(ierr);        
>   ierr = MatMeshToCellGraph(AL,2,&dual);CHKERRQ(ierr); 
>   ierr = MatPartitioningCreate(MPI_COMM_WORLD,&part);CHKERRQ(ierr);
>   ierr = MatPartitioningSetAdjacency(part,dual);CHKERRQ(ierr);               
>   ierr = MatPartitioningSetFromOptions(part);CHKERRQ(ierr);
>   ierr = MatPartitioningApply(part,&partitioning);CHKERRQ(ierr);
>   ierr = ISView(partitioning,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);       
>   ierr = ISDestroy(&partitioning);CHKERRQ(ierr);
>   ierr = MatPartitioningDestroy(&part);CHKERRQ(ierr);
> 
> However, when I look at partitioning with ISView, the index set consists of zeros only. Is that because I have only one processor and my codes are written for only one processor, or is there another problem? I ran my code with -mat_partitioning_type parmetis.
> 
> Thanks,
> 
> Eda