Hello,
I am developing code in the Step-40 like setting - Cahn-
Hilliard Navier Stokes system. I am witnessing very poor
performance of startup for large problems.
For the system with
1458 dof for Cahn Hilliard
47000 dofs for Navier Stoke
I got the following results (4 computer cores)
Setup CH, wall time: 0.1601s.
Setup NS, wall time: 29.9953s.
Setup, wall time: 30.1752s.
The times deteriorate if I solve larger problems.
I guess, that there is something wrong with my setup function
for the Navier-Stokes part of the system.
Could You help me please to find out, where is the performance flaw?
I use namespace ::LinearAlgebraTrilinos for backend of computations.
LA::MPI::Vector locally_relevant_solution_nse;
LA::MPI::Vector old_solution_nse;
LA::MPI::Vector solution_nse;
IndexSet locally_owned_dofs_nse;
IndexSet locally_relevant_dofs_nse;
{
computing_timer.enter_subsection("Setup NS");
dof_handler_nse.distribute_dofs(fe_nse);
DoFRenumbering::Cuthill_McKee(dof_handler_nse);
locally_owned_dofs_nse = dof_handler_nse.locally_owned_dofs();
DoFTools::extract_locally_relevant_dofs(dof_handler_nse,
locally_relevant_dofs_nse);
locally_relevant_solution_nse.reinit(locally_owned_dofs_nse,
locally_relevant_dofs_nse, mpi_communicator);
old_solution_nse.reinit(locally_owned_dofs_nse,
locally_relevant_dofs_nse, mpi_communicator);
old_solution_nse = 0;
solution_nse.reinit(locally_owned_dofs_nse,
locally_relevant_dofs_nse,
mpi_communicator);
system_rhs_nse.reinit(locally_owned_dofs_nse, mpi_communicator);
system_rhs_nse = 0;
constraint_matrix_nse.clear();
constraint_matrix_nse.reinit(locally_relevant_dofs_nse);
DoFTools::make_hanging_node_constraints(dof_handler_nse,
constraint_matrix_nse);
std::vector<bool> component_mask(dim + 1, false);
for (int i = 0; i < dim; ++i)
component_mask[i] = true; // velocities
VectorTools::interpolate_boundary_values(dof_handler_nse, 0,
ConstantFunction<dim>(0., dim + 1), constraint_matrix_nse,
component_mask);
VectorTools::interpolate_boundary_values(dof_handler_nse, 1,
InflowVelocityBoundaryValues<dim>(), constraint_matrix_nse,
component_mask);
constraint_matrix_nse.close();
LA::Vector<double> vec_old_solution(dof_handler_nse.n_dofs());
VectorTools::interpolate(dof_handler_nse, ZeroFunction<3>(dim + 1),
vec_old_solution);
old_solution_nse = vec_old_solution;
DynamicSparsityPattern csp(locally_relevant_dofs_nse);
DoFTools::make_sparsity_pattern(dof_handler_nse, csp,
constraint_matrix_nse, false);
SparsityTools::distribute_sparsity_pattern(csp,
dof_handler_nse.n_locally_owned_dofs_per_processor(),
mpi_communicator, locally_relevant_dofs_nse);
system_matrix_nse.reinit(locally_owned_dofs_nse,
locally_owned_dofs_nse,
csp, mpi_communicator);
computing_timer.leave_subsection();
}
Thank You
Marek C
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