Actual source code: ex14.c

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

  3: #include <petscmat.h>

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

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

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

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

 65: /*TEST

 67:    test:

 69: TEST*/