1: static char help[] = "Example of using graph partitioning with a matrix in which some procs have empty ownership\n\n";

  3: #include <petscmat.h>

  5: int main(int argc, char **args)
  6: {
  7:   Mat             A;
  8:   MatPartitioning part;
  9:   IS              is;
 10:   PetscInt        i, m, N, rstart, rend, nemptyranks, *emptyranks, nbigranks, *bigranks;
 11:   PetscMPIInt     rank, size;

 13:   PetscFunctionBeginUser;
 14:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 15:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
 16:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));

 18:   nemptyranks = 10;
 19:   nbigranks   = 10;
 20:   PetscCall(PetscMalloc2(nemptyranks, &emptyranks, nbigranks, &bigranks));

 22:   PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "Partitioning example options", NULL);
 23:   PetscCall(PetscOptionsIntArray("-emptyranks", "Ranks to be skipped by partition", "", emptyranks, &nemptyranks, NULL));
 24:   PetscCall(PetscOptionsIntArray("-bigranks", "Ranks to be overloaded", "", bigranks, &nbigranks, NULL));
 25:   PetscOptionsEnd();

 27:   m = 1;
 28:   for (i = 0; i < nemptyranks; i++)
 29:     if (rank == emptyranks[i]) m = 0;
 30:   for (i = 0; i < nbigranks; i++)
 31:     if (rank == bigranks[i]) m = 5;

 33:   PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
 34:   PetscCall(MatSetSizes(A, m, m, PETSC_DECIDE, PETSC_DECIDE));
 35:   PetscCall(MatSetFromOptions(A));
 36:   PetscCall(MatSeqAIJSetPreallocation(A, 3, NULL));
 37:   PetscCall(MatMPIAIJSetPreallocation(A, 3, NULL, 2, NULL));
 38:   PetscCall(MatSeqBAIJSetPreallocation(A, 1, 3, NULL));
 39:   PetscCall(MatMPIBAIJSetPreallocation(A, 1, 3, NULL, 2, NULL));
 40:   PetscCall(MatSeqSBAIJSetPreallocation(A, 1, 2, NULL));
 41:   PetscCall(MatMPISBAIJSetPreallocation(A, 1, 2, NULL, 1, NULL));

 43:   PetscCall(MatGetSize(A, NULL, &N));
 44:   PetscCall(MatGetOwnershipRange(A, &rstart, &rend));
 45:   for (i = rstart; i < rend; i++) {
 46:     const PetscInt    cols[] = {(i + N - 1) % N, i, (i + 1) % N};
 47:     const PetscScalar vals[] = {1, 1, 1};
 48:     PetscCall(MatSetValues(A, 1, &i, 3, cols, vals, INSERT_VALUES));
 49:   }
 50:   PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
 51:   PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
 52:   PetscCall(MatView(A, PETSC_VIEWER_STDOUT_WORLD));

 54:   PetscCall(MatPartitioningCreate(PETSC_COMM_WORLD, &part));
 55:   PetscCall(MatPartitioningSetAdjacency(part, A));
 56:   PetscCall(MatPartitioningSetFromOptions(part));
 57:   PetscCall(MatPartitioningApply(part, &is));
 58:   PetscCall(ISView(is, PETSC_VIEWER_STDOUT_WORLD));
 59:   PetscCall(ISDestroy(&is));
 60:   PetscCall(MatPartitioningDestroy(&part));
 61:   PetscCall(MatDestroy(&A));
 62:   PetscCall(PetscFree2(emptyranks, bigranks));
 63:   PetscCall(PetscFinalize());
 64:   return 0;
 65: }

 67: /*TEST

 69:    test:
 70:       nsize: 8
 71:       args: -emptyranks 0,2,4 -bigranks 1,3,7 -mat_partitioning_type average
 72:       # cannot test with external package partitioners since they produce different results on different systems

 74: TEST*/