Hello,
I am facing an issue when I use hanging nodes with periodic boundary
conditions. I have reproduced the error in the attached minimal example
where I do the following steps:
1) Create a hypercube
2) Set appropriate boundary_ids on the faces of the hypercube for periodic
boundary conditions, call collect_periodic_faces and
triangulation.add_periodicity.
3) Perform two levels of mesh refinement:- a) first one step uniform
refinement hypercube to get 8 cells ,and b) then pick one of the 8 cells
and refine only that cell which creates hanging nodes on the faces. Finally
I get 15 cells (see attached image).
4) Create constraintMatrix which includes both hanging node and periodic
constraints.
*The issue:*
If I flip the boundary ids of the face pairs while marking the faces of
the hypercube in step-2 (change Ltemp=L in line 62 to Ltemp=-L), the size
of the constraint matrix created in step-4 changes. Further investigation
of the constraint matrix entries in the two cases revealed
that the number of identity_constraints are different- in one case it gives
19 identity_constraints and 17 in the other case. Manually counting the
numbering of identity_constraints using the attached image gives 19.
Is it correct to expect the size of the constraint matrix to remain
unchanged in the above case?
Additional note: The minimal example doesn't throw any error in the debug
mode. I am using deal ii version 8.5.1 and serial triangulation.
Thanks,
Sambit
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//Include all deal.II header file
#include <deal.II/base/quadrature.h>
#include <deal.II/base/function.h>
#include <deal.II/base/logstream.h>
#include <deal.II/base/timer.h>
#include <deal.II/base/table.h>
#include <deal.II/lac/vector.h>
#include <deal.II/lac/full_matrix.h>
#include <deal.II/lac/constraint_matrix.h>
#include <deal.II/fe/fe_system.h>
#include <deal.II/fe/fe_q.h>
#include <deal.II/fe/fe_values.h>
#include <deal.II/fe/mapping_q1.h>
#include <deal.II/grid/tria.h>
#include <deal.II/grid/tria_accessor.h>
#include <deal.II/grid/tria_iterator.h>
#include <deal.II/grid/grid_generator.h>
#include <deal.II/dofs/dof_tools.h>
#include <deal.II/dofs/dof_handler.h>
#include <deal.II/numerics/data_out.h>
#include <deal.II/numerics/vector_tools.h>
#include <deal.II/base/tensor_function.h>
#include <deal.II/base/point.h>
#include <deal.II/base/conditional_ostream.h>
#include <deal.II/base/utilities.h>
#include <deal.II/lac/lapack_full_matrix.h>
#include <deal.II/numerics/matrix_tools.h>
#include <deal.II/numerics/error_estimator.h>
#include <deal.II/base/parameter_handler.h>
#include <deal.II/grid/grid_refinement.h>
#include <deal.II/grid/tria_boundary_lib.h>
#include <deal.II/grid/grid_tools.h>
#include <deal.II/grid/grid_in.h>
#include <deal.II/grid/grid_out.h>
#include <deal.II/dofs/dof_renumbering.h>
#include <deal.II/dofs/dof_accessor.h>
#include <deal.II/lac/solver_cg.h>
#include <deal.II/lac/solver_gmres.h>
#include <deal.II/lac/solver_bicgstab.h>
#include <deal.II/lac/precondition.h>
#include <deal.II/distributed/tria.h>
#include <deal.II/lac/parallel_vector.h>
#include <deal.II/matrix_free/matrix_free.h>
#include <deal.II/matrix_free/fe_evaluation.h>
#include <deal.II/lac/slepc_solver.h>
#include <deal.II/base/config.h>
#include <deal.II/base/smartpointer.h>
//Include generic C++ headers
#include <fstream>
#include <iostream>
using namespace dealii;
int main (int argc, char *argv[])
{
Utilities::MPI::MPI_InitFinalize mpi_initialization(argc, argv);
const double L=20;
Triangulation<3,3> triangulation;
GridGenerator::hyper_cube (triangulation, -L, L);
const double Ltemp=L;//FIXME: Size of constraint matrix changes between Ltemp=L, and Ltemp=-L;
//mark faces
typename Triangulation<3,3>::active_cell_iterator cell = triangulation.begin_active(), endc = triangulation.end();
for(; cell!=endc; ++cell)
{
for(unsigned int f=0; f < GeometryInfo<3>::faces_per_cell; ++f)
{
const Point<3> face_center = cell->face(f)->center();
if(cell->face(f)->at_boundary())
{
if (std::abs(face_center[0]-Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(1);
else if (std::abs(face_center[0]+Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(2);
else if (std::abs(face_center[1]-Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(3);
else if (std::abs(face_center[1]+Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(4);
else if (std::abs(face_center[2]-Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(5);
else if (std::abs(face_center[2]+Ltemp)<1.0e-5)
cell->face(f)->set_boundary_id(6);
}
}
}
std::vector<GridTools::PeriodicFacePair<typename Triangulation<3,3>::cell_iterator> > periodicity_vector;
for (int i = 0; i < 3; ++i)
{
GridTools::collect_periodic_faces(triangulation, /*b_id1*/ 2*i+1, /*b_id2*/ 2*i+2,/*direction*/ i, periodicity_vector);
}
triangulation.add_periodicity(periodicity_vector);
//two level mesh refinement
triangulation.refine_global(1);
typename Triangulation<3,3>::active_cell_iterator cellBegin = triangulation.begin_active();
cellBegin->set_refine_flag();
triangulation.execute_coarsening_and_refinement();
std::cout << "number of elements: "
<< triangulation.n_global_active_cells()
<< std::endl;
/////
FESystem<3> FE(FE_Q<3>(QGaussLobatto<1>(2)), 1); //linear shape function
DoFHandler<3> dofHandler (triangulation);
dofHandler.distribute_dofs(FE);
///creating constraint matrix
ConstraintMatrix constraints;
constraints.clear();
std::cout<< "Adding hanging node constraints... "<< std::endl;
DoFTools::make_hanging_node_constraints(dofHandler, constraints);
std::cout<< "Adding periodicity constraints... "<< std::endl;
std::vector<GridTools::PeriodicFacePair<typename DoFHandler<3>::cell_iterator> > periodicity_vectorDof;
for (int i = 0; i < 3; ++i)
{
GridTools::collect_periodic_faces(dofHandler, /*b_id1*/ 2*i+1, /*b_id2*/ 2*i+2,/*direction*/ i, periodicity_vectorDof);
}
DoFTools::make_periodicity_constraints<DoFHandler<3> >(periodicity_vectorDof, constraints);
constraints.close();
std::cout<< "size of constraint matrix: "<< constraints.n_constraints()<<std::endl;
std::cout<< "printing constraint matrix ...."<<std::endl;
constraints.print(std::cout);
/////write mesh
std::cout<<"writing mesh .." <<std::endl;
DataOut<3> data_out;
data_out.attach_dof_handler(dofHandler);
data_out.build_patches ();
std::ofstream output("mesh.vtu");
data_out.write_vtu (output);
}
