Hi Seyed,
If you're wanting the infinity norm of a deal.II vector, then there's already
a function
<https://www.dealii.org/8.4.1/doxygen/deal.II/classVector.html#a6e60ea952a6d3185b2f63f24e273329c>
for that. You can find the equivalent function for the specific MPI vector
class that you're using in its documentation.
Regards,
Jean-Paul
On Sunday, February 26, 2017 at 3:35:58 PM UTC+1, Seyed Ali Mohseni wrote:
>
> Thank you everyone. I understand your suggestions. From what I learned now
> in deal.II is, that each cell is owned by a specific processor which means
> I cannot access the information within a locally owned cell. That's why I
> have to loop over all cells and work with distributed data without using
> locally owned entities.
>
> Maybe I describe my aim more properly. I like to find the maximum value
> within a MPI vector such as our locally_relevant_solution in step-40.
> Hence, I have to loop over all cells and all nodes to find where the
> geometrical position and value of the displacement lies. How is this
> possible within a parallely distributed environment?
>
> My approach using local_dof_indices is somehow impossible. It only works
> for 1 core according to the below code:
>
> std::vector<double> displacement_norms, loaded_nodes, loaded_elements;
> double max_displacement;
> int max_loaded_node, max_loaded_element;
>
> typename DoFHandler<dim>::active_cell_iterator cell =
> dof_handler.begin_active(), endc = dof_handler.end();
> std::vector<unsigned int> local_dof_indices(fe.dofs_per_cell);
> unsigned int cell_number = 0;
>
> for (; cell != endc; ++cell, ++cell_number)
> {
> pcout << "CELL ID: " << cell_number << std::endl; // this works
> surprisingly.
>
> cell->get_dof_indices(local_dof_indices); // Output or accessing
> this won't work I assume.
>
> for (unsigned int i = 0, j = 1; i < fe.dofs_per_cell; i += 2, j += 2)
> {
> double displacement_x = locally_relevant_solution(local_dof_indices[i]);
> double displacement_y = locally_relevant_solution(local_dof_indices[j]);
>
> double displacement_norm = sqrt(displacement_x * displacement_x
> + displacement_y * displacement_y);
>
> loaded_nodes.push_back(cell->vertex_index(v));
> loaded_elements.push_back(cell_number);
> displacement_norms.push_back(displacement_norm);
> }
> }
>
> max_displacement = *max_element(displacement_norms.begin(),
> displacement_norms.end());
>
> double max_index = distance(displacement_norms.begin(), max_element(
> displacement_norms.begin(), displacement_norms.end()));
>
> // Node and element number of maximal displacements
> max_loaded_node = loaded_nodes[max_index];
> max_loaded_element = loaded_elements[max_index];
>
>
> Hopefully someone has an idea to help me out. Thank you :)
>
>
> Kind regards,
> S. A. Mohseni
>
>
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