Actual source code: ex14.c


  2: static char help[] = "Tests sequential and parallel MatGetRow() and MatRestoreRow().\n";

  4: #include <petscmat.h>

  6: int main(int argc, char **args)
  7: {
  8:   Mat                C;
  9:   PetscInt           i, j, m = 5, n = 5, Ii, J, nz, rstart, rend;
 10:   PetscMPIInt        rank;
 11:   const PetscInt    *idx;
 12:   PetscScalar        v;
 13:   const PetscScalar *values;

 16:   PetscInitialize(&argc, &args, (char *)0, help);
 17:   /* Create the matrix for the five point stencil, YET AGAIN */
 18:   MatCreate(PETSC_COMM_WORLD, &C);
 19:   MatSetSizes(C, PETSC_DECIDE, PETSC_DECIDE, m * n, m * n);
 20:   MatSetFromOptions(C);
 21:   MatSetUp(C);
 22:   for (i = 0; i < m; i++) {
 23:     for (j = 0; j < n; j++) {
 24:       v  = -1.0;
 25:       Ii = j + n * i;
 26:       if (i > 0) {
 27:         J = Ii - n;
 28:         MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES);
 29:       }
 30:       if (i < m - 1) {
 31:         J = Ii + n;
 32:         MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES);
 33:       }
 34:       if (j > 0) {
 35:         J = Ii - 1;
 36:         MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES);
 37:       }
 38:       if (j < n - 1) {
 39:         J = Ii + 1;
 40:         MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES);
 41:       }
 42:       v = 4.0;
 43:       MatSetValues(C, 1, &Ii, 1, &Ii, &v, INSERT_VALUES);
 44:     }
 45:   }
 46:   MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY);
 47:   MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY);
 48:   MatView(C, PETSC_VIEWER_STDOUT_WORLD);

 50:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);
 51:   MatGetOwnershipRange(C, &rstart, &rend);
 52:   for (i = rstart; i < rend; i++) {
 53:     MatGetRow(C, i, &nz, &idx, &values);
 54:     if (rank == 0) {
 55:       for (j = 0; j < nz; j++) PetscPrintf(PETSC_COMM_SELF, "%" PetscInt_FMT " %g ", idx[j], (double)PetscRealPart(values[j]));
 56:       PetscPrintf(PETSC_COMM_SELF, "\n");
 57:     }
 58:     MatRestoreRow(C, i, &nz, &idx, &values);
 59:   }

 61:   MatDestroy(&C);
 62:   PetscFinalize();
 63:   return 0;
 64: }

 66: /*TEST

 68:    test:

 70: TEST*/