From: Sebastian Stark <stark.sebastian@gmx.de>
Date: Tue, 8 Oct 2019 11:53:47 +0000 (+0200)
Subject: Fix a bug in merge triangulations()
X-Git-Tag: v9.2.0-rc1~990^2~2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=de582145eb28dbd728a226cb80e185def874cae6;p=dealii.git

Fix a bug in merge triangulations()

This patch makes sure that merge_triangulations() does not forget about where the boundary is (the problem has actually been in create_triangulation(), which assigned numbers::internal_face_boundary_id to boundary_faces)
---

diff --git a/doc/news/changes/minor/20191008SebastianStark b/doc/news/changes/minor/20191008SebastianStark
new file mode 100644
index 0000000000..426975d3c6
--- /dev/null
+++ b/doc/news/changes/minor/20191008SebastianStark
@@ -0,0 +1,6 @@
+Fixed: Make sure that merge_triangulations() does
+not forget about where the boundary is (the problem has
+actually been in create_triangulation(), which assigned
+numbers::internal_face_boundary_id to boundary faces)
+<br>
+(Sebastian Stark, 2019/10/08)
diff --git a/source/grid/tria.cc b/source/grid/tria.cc
index da64da1b3a..09b6b586aa 100644
--- a/source/grid/tria.cc
+++ b/source/grid/tria.cc
@@ -3166,8 +3166,11 @@ namespace internal
                             ExcInconsistentLineInfoOfLine(line_vertices.first,
                                                           line_vertices.second,
                                                           "boundary ids"));
-
-                line->set_boundary_id_internal(subcell_line.boundary_id);
+                // do not use the boundary id provided in subcell_line
+                // if it is an internal one
+                if (subcell_line.boundary_id !=
+                    numbers::internal_face_boundary_id)
+                  line->set_boundary_id_internal(subcell_line.boundary_id);
               }
             // Set manifold id if given
             AssertThrow(line->manifold_id() == numbers::flat_manifold_id ||
@@ -3317,8 +3320,11 @@ namespace internal
                                                           line[2]->index(),
                                                           line[3]->index(),
                                                           "boundary ids"));
-
-                quad->set_boundary_id_internal(subcell_quad.boundary_id);
+                // do not use the boundary id provided in subcell_quad
+                // if it is an invalid or internal one
+                if (subcell_quad.boundary_id !=
+                    numbers::internal_face_boundary_id)
+                  quad->set_boundary_id_internal(subcell_quad.boundary_id);
               }
             // Set manifold id if given
             if (quad->manifold_id() != numbers::flat_manifold_id)
diff --git a/tests/grid/merge_triangulations_07.cc b/tests/grid/merge_triangulations_07.cc
new file mode 100644
index 0000000000..03fb15cc33
--- /dev/null
+++ b/tests/grid/merge_triangulations_07.cc
@@ -0,0 +1,61 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2018 - 2019 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// ---------------------------------------------------------------------
+
+
+
+// Test for a patch which makes sure that merge_triangulations() does
+// not forget about where the boundary is (the problem has
+// actually been in create_triangulation(), which assigned
+// numbers::internal_face_boundary_id to boundary faces)
+
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/grid_tools.h>
+
+#include "../tests.h"
+
+using namespace dealii;
+
+int
+main()
+{
+  initlog();
+
+  const unsigned int spacedim = 3;
+
+  Triangulation<spacedim> tria_0, tria_1, tria_2;
+
+  GridGenerator::hyper_cube(tria_0);
+  GridGenerator::hyper_cube(tria_1);
+  Tensor<1, spacedim> shift;
+  shift[0] = 1.0;
+  GridTools::shift(shift, tria_1);
+
+  tria_0.set_all_manifold_ids(0);
+  tria_1.set_all_manifold_ids(0);
+  GridGenerator::merge_triangulations(tria_0, tria_1, tria_2, 1e-12, true);
+
+  unsigned int boundary_face_count = 0;
+  for (const auto &cell : tria_2.active_cell_iterators())
+    for (unsigned int f = 0; f < GeometryInfo<spacedim>::faces_per_cell; ++f)
+      if (cell->face(f)->at_boundary())
+        ++boundary_face_count;
+
+  if (boundary_face_count != 10)
+    deallog << "Found " << boundary_face_count
+            << " boundary faces. However, there should be 10 of them!"
+            << std::endl;
+  else
+    deallog << "OK!" << std::endl;
+}
diff --git a/tests/grid/merge_triangulations_07.output b/tests/grid/merge_triangulations_07.output
new file mode 100644
index 0000000000..5cfb783b8f
--- /dev/null
+++ b/tests/grid/merge_triangulations_07.output
@@ -0,0 +1,2 @@
+
+DEAL::OK!