Date: 2021-03-03T22:26:39+00:00

Actual source code: ex15.c
petsc-3.14.5 2021-03-03
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      1: static char help[] = "Example of using graph partitioning to partition a graph\n\n";

      3: /*T
      4:    Concepts: Mat^mat partitioning
      5:    Concepts: Mat^image segmentation
      6:    Processors: n
      7: T*/

      9: #include <petscmat.h>

     11: int main(int argc, char **args)
     12: {
     13:   Mat             A;
     14:   MatPartitioning part;
     15:   IS              is;
     16:   PetscInt        r,N = 10, start, end, *vweights;
     17:   PetscBool       set_vweights=PETSC_FALSE,use_edge_weights=PETSC_FALSE;
     18:   PetscMPIInt     rank;
     19:   MPI_Comm        comm;
     20:   PetscErrorCode  ierr;

     22:   PetscInitialize(&argc, &args, (char*) 0, help);if (ierr) return ierr;
     23:   comm = PETSC_COMM_WORLD;
     24:   PetscOptionsGetInt(NULL,NULL, "-N", &N, NULL);
     25:   MPI_Comm_rank(comm,&rank);
     26:   MatCreate(comm, &A);
     27:   MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, N, N);
     28:   MatSetFromOptions(A);
     29:   MatSeqAIJSetPreallocation(A, 3, NULL);
     30:   MatMPIAIJSetPreallocation(A, 3, NULL, 2, NULL);
     31:   PetscOptionsGetBool(NULL,NULL,"-test_vertex_weights",&set_vweights,NULL);
     32:   PetscOptionsGetBool(NULL,NULL,"-test_use_edge_weights",&use_edge_weights,NULL);
     33:   /* Create a linear mesh */
     34:   MatGetOwnershipRange(A, &start, &end);
     35:   if (set_vweights) {
     36:     PetscMalloc1(end-start,&vweights);
     37:     for (r = start; r < end; ++r)
     38:       vweights[r-start] = rank+1;
     39:   }
     40:   for (r = start; r < end; ++r) {
     41:     if (r == 0) {
     42:       PetscInt    cols[2];
     43:       PetscScalar vals[2];

     45:       cols[0] = r;   cols[1] = r+1;
     46:       vals[0] = 1.0; vals[1] = use_edge_weights? 2.0: 1.0;

     48:       MatSetValues(A, 1, &r, 2, cols, vals, INSERT_VALUES);
     49:     } else if (r == N-1) {
     50:       PetscInt    cols[2];
     51:       PetscScalar vals[2];

     53:       cols[0] = r-1; cols[1] = r;
     54:       vals[0] = use_edge_weights? 3.0:1.0; vals[1] = 1.0;

     56:       MatSetValues(A, 1, &r, 2, cols, vals, INSERT_VALUES);
     57:     } else {
     58:       PetscInt    cols[3];
     59:       PetscScalar vals[3];

     61:       cols[0] = r-1; cols[1] = r;   cols[2] = r+1;
     62:       /* ADJ matrix needs to be symmetric */
     63:       vals[0] = use_edge_weights? (cols[0]==0? 2.0:5.0):1.0;
     64:       vals[1] = 1.0;
     65:       vals[2] = use_edge_weights? (cols[2]==N-1? 3.0:5.0):1.0;

     67:       MatSetValues(A, 1, &r, 3, cols, vals, INSERT_VALUES);
     68:     }
     69:   }
     70:   MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY);
     71:   MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY);

     73:   MatPartitioningCreate(comm, &part);
     74:   MatPartitioningSetAdjacency(part, A);
     75:   if (set_vweights) {
     76:     MatPartitioningSetVertexWeights(part,vweights);
     77:   }
     78:   if (use_edge_weights) {
     79:     MatPartitioningSetUseEdgeWeights(part,use_edge_weights);

     81:     MatPartitioningGetUseEdgeWeights(part,&use_edge_weights);
     82:     if (!use_edge_weights) SETERRQ(comm,PETSC_ERR_ARG_INCOMP, "use_edge_weights flag does not setup correctly \n");
     83:   }
     84:   MatPartitioningSetFromOptions(part);
     85:   MatPartitioningApply(part, &is);
     86:   ISView(is, PETSC_VIEWER_STDOUT_WORLD);
     87:   ISDestroy(&is);
     88:   MatPartitioningDestroy(&part);

     90:   MatDestroy(&A);
     91:   PetscFinalize();
     92:   return ierr;
     93: }

     96: /*TEST

     98:    test:
     99:       nsize: 3
    100:       requires: parmetis
    101:       args: -mat_partitioning_type parmetis

    103:    test:
    104:       suffix: 2
    105:       nsize: 3
    106:       requires: ptscotch
    107:       args: -mat_partitioning_type ptscotch

    109:    test:
    110:       suffix: 3
    111:       nsize: 4
    112:       requires: party
    113:       args: -mat_partitioning_type party

    115:    test:
    116:       suffix: 4
    117:       nsize: 3
    118:       requires: chaco
    119:       args: -mat_partitioning_type chaco

    121:    test:
    122:       suffix: 5
    123:       nsize: 3
    124:       requires: parmetis
    125:       args: -mat_partitioning_type hierarch -mat_partitioning_hierarchical_nfineparts 3 -mat_partitioning_nparts 10 -N 100

    127:    test:
    128:       suffix: 6
    129:       nsize: 3
    130:       requires: parmetis
    131:       args: -mat_partitioning_type hierarch -mat_partitioning_hierarchical_nfineparts 3 -mat_partitioning_nparts 10 -N 100 -test_vertex_weights 1 -mat_partitioning_use_edge_weights 1

    133:    test:
    134:       suffix: 7
    135:       nsize: 2
    136:       requires: parmetis
    137:       args: -mat_partitioning_type hierarch -mat_partitioning_hierarchical_nfineparts 2 -mat_partitioning_nparts 10  -mat_partitioning_hierarchical_fineparttype hierarch -malloc_dump -N 100 -mat_partitioning_improve 1

    139:    test:
    140:       suffix: 8
    141:       nsize: 2
    142:       requires: parmetis
    143:       args: -mat_partitioning_type parmetis -mat_partitioning_nparts 3 -test_use_edge_weights 1

    145:    test:
    146:       suffix: 9
    147:       nsize: 2
    148:       requires: ptscotch
    149:       args: -mat_partitioning_type ptscotch -mat_partitioning_nparts 3 -test_use_edge_weights 1 -mat_partitioning_ptscotch_proc_weight 0

    151: TEST*/