1: static char help[] = "Tests 1D Gauss-Lobatto-Legendre discretization on [-1, 1].\n\n";

  3: #include <petscdt.h>

  5: int main(int argc, char **argv)
  6: {
  7:   PetscInt   n = 3, i;
  8:   PetscReal *la_nodes, *la_weights, *n_nodes, *n_weights;

 10:   PetscFunctionBeginUser;
 11:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
 12:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

 14:   PetscCall(PetscMalloc1(n, &la_nodes));
 15:   PetscCall(PetscMalloc1(n, &la_weights));
 16:   PetscCall(PetscMalloc1(n, &n_nodes));
 17:   PetscCall(PetscMalloc1(n, &n_weights));
 18:   PetscCall(PetscDTGaussLobattoLegendreQuadrature(n, PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA, la_nodes, la_weights));

 20:   PetscCall(PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_SELF, "Gauss-Lobatto-Legendre nodes and weights computed via linear algebra: \n"));
 21:   PetscCall(PetscRealView(n, la_nodes, PETSC_VIEWER_STDOUT_SELF));
 22:   PetscCall(PetscRealView(n, la_weights, PETSC_VIEWER_STDOUT_SELF));
 23:   PetscCall(PetscDTGaussLobattoLegendreQuadrature(n, PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON, n_nodes, n_weights));
 24:   PetscCall(PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_SELF, "Gauss-Lobatto-Legendre nodes and weights computed via Newton: \n"));
 25:   PetscCall(PetscRealView(n, n_nodes, PETSC_VIEWER_STDOUT_SELF));
 26:   PetscCall(PetscRealView(n, n_weights, PETSC_VIEWER_STDOUT_SELF));

 28:   for (i = 0; i < n; i++) {
 29:     la_nodes[i] -= n_nodes[i];
 30:     la_weights[i] -= n_weights[i];
 31:   }
 32:   PetscCall(PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_SELF, "Difference: \n"));
 33:   PetscCall(PetscRealView(n, la_nodes, PETSC_VIEWER_STDOUT_SELF));
 34:   PetscCall(PetscRealView(n, la_weights, PETSC_VIEWER_STDOUT_SELF));

 36:   PetscCall(PetscFree(la_nodes));
 37:   PetscCall(PetscFree(la_weights));
 38:   PetscCall(PetscFree(n_nodes));
 39:   PetscCall(PetscFree(n_weights));

 41:   PetscCall(PetscFinalize());
 42:   return 0;
 43: }

 45: /*TEST

 47:    test:

 49: TEST*/