Actual source code: ex80.c


  2: static char help[] = "Partition tiny grid.\n\n";

  4: /*
  5:   Include "petscmat.h" so that we can use matrices.  Note that this file
  6:   automatically includes:
  7:      petscsys.h       - base PETSc routines   petscvec.h - vectors
  8:      petscmat.h - matrices
  9:      petscis.h     - index sets
 10:      petscviewer.h - viewers
 11: */
 12: #include <petscmat.h>

 14: int main(int argc, char **args)
 15: {
 16:   Mat             A, At;
 17:   PetscMPIInt     rank, size;
 18:   PetscInt       *ia, *ja, row;
 19:   MatPartitioning part;
 20:   IS              is, isn;
 21:   PetscBool       equal;

 23:   PetscFunctionBeginUser;
 24:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 25:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 26:   PetscCheck(size == 4, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Must run with 4 processors");
 27:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

 29:   PetscCall(PetscMalloc1(5, &ia));
 30:   PetscCall(PetscMalloc1(16, &ja));
 31:   if (rank == 0) {
 32:     ja[0] = 1;
 33:     ja[1] = 4;
 34:     ja[2] = 0;
 35:     ja[3] = 2;
 36:     ja[4] = 5;
 37:     ja[5] = 1;
 38:     ja[6] = 3;
 39:     ja[7] = 6;
 40:     ja[8] = 2;
 41:     ja[9] = 7;
 42:     ia[0] = 0;
 43:     ia[1] = 2;
 44:     ia[2] = 5;
 45:     ia[3] = 8;
 46:     ia[4] = 10;
 47:   } else if (rank == 1) {
 48:     ja[0]  = 0;
 49:     ja[1]  = 5;
 50:     ja[2]  = 8;
 51:     ja[3]  = 1;
 52:     ja[4]  = 4;
 53:     ja[5]  = 6;
 54:     ja[6]  = 9;
 55:     ja[7]  = 2;
 56:     ja[8]  = 5;
 57:     ja[9]  = 7;
 58:     ja[10] = 10;
 59:     ja[11] = 3;
 60:     ja[12] = 6;
 61:     ja[13] = 11;
 62:     ia[0]  = 0;
 63:     ia[1]  = 3;
 64:     ia[2]  = 7;
 65:     ia[3]  = 11;
 66:     ia[4]  = 14;
 67:   } else if (rank == 2) {
 68:     ja[0]  = 4;
 69:     ja[1]  = 9;
 70:     ja[2]  = 12;
 71:     ja[3]  = 5;
 72:     ja[4]  = 8;
 73:     ja[5]  = 10;
 74:     ja[6]  = 13;
 75:     ja[7]  = 6;
 76:     ja[8]  = 9;
 77:     ja[9]  = 11;
 78:     ja[10] = 14;
 79:     ja[11] = 7;
 80:     ja[12] = 10;
 81:     ja[13] = 15;
 82:     ia[0]  = 0;
 83:     ia[1]  = 3;
 84:     ia[2]  = 7;
 85:     ia[3]  = 11;
 86:     ia[4]  = 14;
 87:   } else {
 88:     ja[0] = 8;
 89:     ja[1] = 13;
 90:     ja[2] = 9;
 91:     ja[3] = 12;
 92:     ja[4] = 14;
 93:     ja[5] = 10;
 94:     ja[6] = 13;
 95:     ja[7] = 15;
 96:     ja[8] = 11;
 97:     ja[9] = 14;
 98:     ia[0] = 0;
 99:     ia[1] = 2;
100:     ia[2] = 5;
101:     ia[3] = 8;
102:     ia[4] = 10;
103:   }

105:   PetscCall(MatCreateMPIAdj(PETSC_COMM_WORLD, 4, 16, ia, ja, NULL, &A));
106:   PetscCall(MatView(A, PETSC_VIEWER_STDOUT_WORLD));

108:   /* Create the same matrix but using MatSetValues() */
109:   PetscCall(MatCreate(PETSC_COMM_WORLD, &At));
110:   PetscCall(MatSetSizes(At, 4, 4, 16, 16));
111:   PetscCall(MatSetType(At, MATMPIADJ));
112:   for (PetscInt i = 0; i < 4; i++) {
113:     row = i + 4 * rank;
114:     PetscCall(MatSetValues(At, 1, &row, ia[i + 1] - ia[i], ja + ia[i], NULL, INSERT_VALUES));
115:   }
116:   PetscCall(MatAssemblyBegin(At, MAT_FINAL_ASSEMBLY));
117:   PetscCall(MatAssemblyEnd(At, MAT_FINAL_ASSEMBLY));
118:   PetscCall(MatEqual(A, At, &equal));
119:   PetscCheck(equal, PETSC_COMM_WORLD, PETSC_ERR_PLIB, "Matrices are not equal that should be equal");
120:   PetscCall(MatDestroy(&At));

122:   /*
123:        Partition the graph of the matrix
124:   */
125:   PetscCall(MatPartitioningCreate(PETSC_COMM_WORLD, &part));
126:   PetscCall(MatPartitioningSetAdjacency(part, A));
127:   PetscCall(MatPartitioningSetFromOptions(part));
128:   /* get new processor owner number of each vertex */
129:   PetscCall(MatPartitioningApply(part, &is));
130:   /* get new global number of each old global number */
131:   PetscCall(ISPartitioningToNumbering(is, &isn));
132:   PetscCall(ISView(isn, PETSC_VIEWER_STDOUT_WORLD));
133:   PetscCall(ISDestroy(&is));

135:   PetscCall(ISDestroy(&isn));
136:   PetscCall(MatPartitioningDestroy(&part));

138:   /*
139:        Free work space.  All PETSc objects should be destroyed when they
140:        are no longer needed.
141:   */
142:   PetscCall(MatDestroy(&A));

144:   PetscCall(PetscFinalize());
145:   return 0;
146: }
147: /*
148:    test:
149:      requires: parmetis
150:      args: -mat_view
151:      nsize: 4
152: */