From 95e717acab9196d3c2f447e5c6b34af17e846e6f Mon Sep 17 00:00:00 2001
From: Martin Kronbichler <kronbichler@lnm.mw.tum.de>
Date: Wed, 27 Jan 2016 18:41:16 +0100
Subject: [PATCH] Overload perpare_coarsening_and_refinement for the periodic
 case

---
 include/deal.II/distributed/tria.h            |  8 +++
 include/deal.II/grid/tria.h                   |  2 +-
 source/distributed/tria.cc                    | 50 +++++++++++++++----
 ...ute_mg_dofs_periodicity_02.mpirun=7.output |  4 ++
 4 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/include/deal.II/distributed/tria.h b/include/deal.II/distributed/tria.h
index 4e4184d4e6..7d5a97a824 100644
--- a/include/deal.II/distributed/tria.h
+++ b/include/deal.II/distributed/tria.h
@@ -501,6 +501,14 @@ namespace parallel
        */
       virtual void execute_coarsening_and_refinement ();
 
+      /**
+       * Override the implementation of prepare_coarsening_and_refinement from
+       * the base class. This is necessary if periodic boundaries are enabled
+       * and the level difference over vertices over the periodic boundary
+       * must be not more than 2:1.
+       */
+      virtual bool prepare_coarsening_and_refinement ();
+
       /**
        * Manually repartition the active cells between processors. Normally
        * this repartitioning will happen automatically when calling
diff --git a/include/deal.II/grid/tria.h b/include/deal.II/grid/tria.h
index d243cf37d9..89a1016540 100644
--- a/include/deal.II/grid/tria.h
+++ b/include/deal.II/grid/tria.h
@@ -1897,7 +1897,7 @@ public:
    * This function uses the user flags, so store them if you still need them
    * afterwards.
    */
-  bool prepare_coarsening_and_refinement ();
+  virtual bool prepare_coarsening_and_refinement ();
 
   /*
    * @}
diff --git a/source/distributed/tria.cc b/source/distributed/tria.cc
index fe6b63bd7a..f025a84549 100644
--- a/source/distributed/tria.cc
+++ b/source/distributed/tria.cc
@@ -3192,21 +3192,26 @@ namespace parallel
       }
 
       template <int dim, int spacedim>
-      void enforce_mesh_balance_over_periodic_boundaries
+      bool enforce_mesh_balance_over_periodic_boundaries
       (Triangulation<dim,spacedim> &tria,
        std::vector<GridTools::PeriodicFacePair<typename dealii::Triangulation<dim,spacedim>::cell_iterator> > periodic_face_pairs_level_0)
       {
         if (periodic_face_pairs_level_0.empty())
-          return;
+          return false;
+
+        std::vector<bool> flags_before[2];
+        tria.save_coarsen_flags (flags_before[0]);
+        tria.save_refine_flags (flags_before[1]);
 
         std::vector<unsigned int> topological_vertex_numbering(tria.n_vertices());
         for (unsigned int i=0; i<topological_vertex_numbering.size(); ++i)
           topological_vertex_numbering[i] = i;
         for (unsigned int i=0; i<periodic_face_pairs_level_0.size(); ++i)
           {
-          identify_periodic_vertices_recursively(periodic_face_pairs_level_0[i],
-                                                 topological_vertex_numbering);
+            identify_periodic_vertices_recursively(periodic_face_pairs_level_0[i],
+                                                   topological_vertex_numbering);
           }
+
         // this code is replicated from grid/tria.cc but using an indirection
         // for periodic boundary conditions
         bool continue_iterating = true;
@@ -3316,11 +3321,43 @@ namespace parallel
                       cell->child(child)->clear_coarsen_flag();
               }
           }
+        std::vector<bool> flags_after[2];
+        tria.save_coarsen_flags (flags_after[0]);
+        tria.save_refine_flags (flags_after[1]);
+        return ((flags_before[0] != flags_after[0]) ||
+                (flags_before[1] != flags_after[1]));
       }
     }
 
 
 
+    template <int dim, int spacedim>
+    bool
+    Triangulation<dim,spacedim>::prepare_coarsening_and_refinement()
+    {
+      std::vector<bool> flags_before[2];
+      this->save_coarsen_flags (flags_before[0]);
+      this->save_refine_flags (flags_before[1]);
+
+      do
+        {
+          this->dealii::Triangulation<dim,spacedim>::prepare_coarsening_and_refinement();
+        }
+      // enforce 2:1 mesh balance over periodic boundaries
+      while ((this->smooth_grid & dealii::Triangulation<dim,spacedim>::limit_level_difference_at_vertices)
+             &&
+             enforce_mesh_balance_over_periodic_boundaries(*this,
+                                                           periodic_face_pairs_level_0));
+
+      std::vector<bool> flags_after[2];
+      this->save_coarsen_flags (flags_after[0]);
+      this->save_refine_flags (flags_after[1]);
+      return ((flags_before[0] != flags_after[0]) ||
+              (flags_before[1] != flags_after[1]));
+    }
+
+
+
     template <int dim, int spacedim>
     void
     Triangulation<dim,spacedim>::copy_local_forest_to_triangulation ()
@@ -3471,11 +3508,6 @@ namespace parallel
           // fix all the flags to make sure we have a consistent mesh
           this->prepare_coarsening_and_refinement ();
 
-          // enforce 2:1 mesh balance over periodic boundaries
-          if (this->smooth_grid & dealii::Triangulation<dim,spacedim>::limit_level_difference_at_vertices)
-            enforce_mesh_balance_over_periodic_boundaries(*this,
-                                                          periodic_face_pairs_level_0);
-
           // see if any flags are still set
           mesh_changed = false;
           for (typename Triangulation<dim,spacedim>::active_cell_iterator
diff --git a/tests/mpi/distribute_mg_dofs_periodicity_02.mpirun=7.output b/tests/mpi/distribute_mg_dofs_periodicity_02.mpirun=7.output
index b74e1dedec..eed327ead0 100644
--- a/tests/mpi/distribute_mg_dofs_periodicity_02.mpirun=7.output
+++ b/tests/mpi/distribute_mg_dofs_periodicity_02.mpirun=7.output
@@ -50,6 +50,10 @@ DEAL:1::6_1:0 4294967294
 DEAL:1::6_1:1 4294967294
 DEAL:1::6_1:2 4
 DEAL:1::6_1:3 4
+DEAL:1::8_1:0 4294967294
+DEAL:1::8_1:1 4294967294
+DEAL:1::8_1:2 4294967294
+DEAL:1::8_1:3 4294967294
 DEAL:1::0_2:00 4294967294
 DEAL:1::0_2:01 0
 DEAL:1::0_2:02 0
-- 
2.39.5