> On Aug 29, 2020, at 2:23 PM, Eda Oktay <eda.ok...@metu.edu.tr> wrote:
>
> Hi all,
>
> I am trying to partition a sparse matrix by using ParMETIS. I am converting
> my matrix to adjacency type and then applying partitioning.
You don't need to do this. Just pass your original matrix directly into
MatPartitioningSetAdjacency() it will handle any conversions needed.
Edge weights need to be positive, since they represent how much communication
is to take place over that link. You may need to force your matrix to have all
positive values before giving it to MatPartitioningSetAdjacency and using edge
weights.
I this doesn't work than our code is broken, please send us a simple test case
Question: Why are you partitioning a matrix? Is it for load balancing of
solves or matrix vector products with the matrix? To reduce interprocess
communication during solves or matrix vector products with the matrix? If so
the numerical values in the matrix don't affect load balance or interprocess
communication for these operations.
Barry
> Default, I understood that partitioning doesn't use edge-weights. However,
> when I used the following codes I saw from ex15 and used
> "-test_use_edge_weights 1", I am getting the same results as when I don't
> consider edge weights.
>
> PetscBool use_edge_weights=PETSC_FALSE;
>
> PetscOptionsGetBool(NULL,NULL,"-test_use_edge_weights",&use_edge_weights,NULL);
> if (use_edge_weights) {
> MatPartitioningSetUseEdgeWeights(part,use_edge_weights);
>
> MatPartitioningGetUseEdgeWeights(part,&use_edge_weights);
> if (!use_edge_weights) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,
> "use_edge_weights flag does not setup correctly \n");
> }
>
> My matrix does not consist of 1s and 0s, so I want partitioning to consider
> all the nonzero elements in the matrix as edge weights. Don't
> MatPartitioningSetUseEdgeWeights and MatPartitioningGetUseEdgeWeights do
> that? Should I add something more? In the page of
> MatPartitioningSetUseEdgeWeights, it is written that "If set use_edge_weights
> to TRUE, users need to make sure legal edge weights are stored in an ADJ
> matrix.". How can I make sure of this?
>
> I am trying to compare the use of ParMETIS with the spectral partitioning
> algorithm when I used a weighted Laplacian.
>
> Thanks!
>
> Eda
>
