Hello,
I want to know how apply boundary constraints in a time-dependent,
adaptively refined and distributed memory code. In a time-step, I want
multiple refinements. I could not find such an example in deal.II
tutorial.
I have the following code, with questionable code in red. Basically,
when transferring old solution, I need boundary constraints for one
time-step back. When assembling the system, I need boundary constraints for
the current time-step. But I don't know how to satisfy both.
for (int time_step = 0; time_step < n_time_steps; time_step++) {
time += dt;
old_locally_relevant_solution = locally_relevant_solution;
for (int refine_step = 0; refine_step < n_refine_steps;
refine_step++) {
assemble_system(); // this function accesses
old_locally_relevant_solution and calls
constraints.distribute_local_to_global (...) to add local matrix to global
matrix.
// The boundary constraints were
computed for time - dt, i.e., one time-step back, however, here what we
need is boundary constraints for the current time step.
solve(); // update locally_relevant_solution
if (refine_step+1 < n_refine_steps) {
// Estimate Kelly errors;
...
// Do triangulation, and transfer old solution from old mesh to
new mesh
triangulation.prepare_coarsening_and_refinement();
parallel::distributed::SolutionTransfer<dim,
PETScWrappers::MPI::Vector> soltrans(dof_handler);
soltrans.prepare_for_coarsening_and_refinement(old_locally_relevant_solution);
triangulation.execute_coarsening_and_refinement ();
setup_system(); // reinit vector, matrix and constraints for the
new mesh. The boundary function is computed for time - dt, since that is
the time when old_locally_relevant_solution was computed
PETScWrappers::MPI::Vector
interpolated_solution(locally_owned_dofs, mpi_communicator);
soltrans.interpolate(interpolated_solution);
constraints.distribute(interpolated_solution);
old_locally_relevant_solution = interpolated_solution;
}
}
Thank you!
--Junchao Zhang
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