Hi guys, I have a question on setting the boundary constraints for mg_constrained_dofs object.
In many problems where the only boundary conditions(for AffineConstraints) are Dirichlet BC and hanging nodes, mg_constrained knows them by MGConstrainedDoFs::make_zero_boundary_constraints(the Dirichlet boundary id, not necessarily zero) and MGConstrainedDoFs::initialize(dof_handler)(the hanging nodes), respectively.
However, in case other BC like compute_normal_flux_constraints or compute_no_normal_flux_constraints exists, mg_constrained_dofs has no way to include it. Therefore the MGLevelObject mg_matrices is intrinsically different to global system_matrix. Then mg_matrices[0] cannot be a good approximation of coarsest grid.
Is there some hint for such cases?