Add test where inversion in real_to_unit_cell fails

diff --git a/tests/mappings/mapping_real_to_unit_q1_singular.cc b/tests/mappings/mapping_real_to_unit_q1_singular.cc
new file mode 100644 (file)
index 0000000..717a3c4
--- /dev/null
+++ b/tests/mappings/mapping_real_to_unit_q1_singular.cc
@@ -0,0 +1,68 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2006 - 2016 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 at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+
+
+
+// check that MappingQ1::transform_real_to_unit_cell can handle the case of a
+// singular discriminant. Previously we used to have a division by zero
+
+#include "../tests.h"
+
+#include <deal.II/base/utilities.h>
+#include <deal.II/grid/tria.h>
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/fe/mapping_q1.h>
+
+
+template<int dim>
+void test_real_to_unit_cell()
+{
+  deallog << "dim=" << dim << std::endl;
+
+  Triangulation<dim>   triangulation;
+  GridGenerator::hyper_ball (triangulation);
+
+  Point<dim> point;
+  MappingQGeneric<dim> mapping(1);
+
+  point[1] = -1./(1+std::sqrt(2.0))/std::sqrt(2);
+
+  // check on cell 2
+  typename Triangulation<dim>::cell_iterator cell = triangulation.begin();
+  ++cell;
+  try
+    {
+      mapping.transform_real_to_unit_cell(cell, point);
+    }
+  catch (typename Mapping<dim>::ExcTransformationFailed)
+    {
+      deallog << "Transformation for point " << point << " on cell with "
+              << "center " << cell->center() << " is not invertible" << std::endl;
+    }
+  deallog << "OK" << std::endl;
+}
+
+
+int
+main()
+{
+  std::ofstream logfile ("output");
+  deallog.attach(logfile);
+  deallog.threshold_double(1.e-10);
+
+  test_real_to_unit_cell<2>();
+
+  return 0;
+}

diff --git a/tests/mappings/mapping_real_to_unit_q1_singular.output b/tests/mappings/mapping_real_to_unit_q1_singular.output
new file mode 100644 (file)
index 0000000..bdc167b
--- /dev/null
+++ b/tests/mappings/mapping_real_to_unit_q1_singular.output
@@ -0,0 +1,4 @@
+
+DEAL::dim=2
+DEAL::Transformation for point 0.00000 -0.292893 on cell with center -0.500000 -1.38778e-17 is not invertible
+DEAL::OK