I'd like to simulate four coupled PDEs (with variables A, B, C and D) using
deal.II. At each step in time I'm interested in the maximum and minimum
value of each variable. Therefore, I have to loop over my solution, and
gather the maximum and minimum value of each variable by using
vector_t local_solution;
present_solution.update_ghost_values();
local_solution = present_solution;
IndexSet locally_owned_elements = local_solution.locally_owned_elements();
locally_owned_elements.compress();
for(auto index: present_solution.locally_owned_elements()) {
if(A_value_mask.is_element(locally_owned_elements.index_within_set(index)))
{
max_A_value = std::max(max_A_value,
static_cast<double>(local_solution(index)));
min_A_value = std::min(min_A_value,
static_cast<double>(local_solution(index)));
}
}
To create A_value_mask, I use
const FEValuesExtractors::Scalar surface_A(0);
const ComponentMask surface_A_mask = fe.component_mask(surface_A);
IndexSet A_value_mask = DoFTools::extract_dofs(dof_handler, surface_A_mask);
For 2.4 million elements and four variables (i.e. four calls), this second
part (more specifically the call extract_dofs()) takes ~120 sec., which
takes up ~30% of the total run time. I have to use such a construct three
times in my code, resulting in 360 sec. spend in extracting dofs, and ~40
sec. in the other parts of the program. Is that by design, or is there
something wrong in my code?
Thanks!
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