From 0cf466504d83987adc95a220eb4cd0bf2dfc7d6f Mon Sep 17 00:00:00 2001
From: Martin Kronbichler <martin.kronbichler@rub.de>
Date: Mon, 1 Apr 2024 21:20:36 +0200
Subject: [PATCH] Test case

---
 .../mapping_cartesian_points_real_to_unit.cc  | 109 ++++++++++++++++++
 ...pping_cartesian_points_real_to_unit.output |   7 ++
 2 files changed, 116 insertions(+)
 create mode 100644 tests/mappings/mapping_cartesian_points_real_to_unit.cc
 create mode 100644 tests/mappings/mapping_cartesian_points_real_to_unit.output

diff --git a/tests/mappings/mapping_cartesian_points_real_to_unit.cc b/tests/mappings/mapping_cartesian_points_real_to_unit.cc
new file mode 100644
index 0000000000..67dba27d59
--- /dev/null
+++ b/tests/mappings/mapping_cartesian_points_real_to_unit.cc
@@ -0,0 +1,109 @@
+// ------------------------------------------------------------------------
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// Copyright (C) 2024 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// Part of the source code is dual licensed under Apache-2.0 WITH
+// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
+// governing the source code and code contributions can be found in
+// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
+//
+// ------------------------------------------------------------------------
+
+
+
+// check MappingCartesian::transform_points_real_to_unit_cell, using a case
+// otherwise similar to mapping_points_real_to_unit.cc
+
+#include <deal.II/base/utilities.h>
+
+#include <deal.II/fe/mapping_cartesian.h>
+
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/tria.h>
+
+#include "../tests.h"
+
+
+template <int dim>
+void
+test()
+{
+  Triangulation<dim> triangulation;
+  Point<dim>         lower, upper;
+  for (unsigned int d = 0; d < dim; ++d)
+    lower[d] = -0.3 + d * 0.07;
+  for (unsigned int d = 0; d < dim; ++d)
+    upper[d] = 0.45 - d * 0.03;
+
+  GridGenerator::hyper_rectangle(triangulation, lower, upper);
+
+  deallog << "dim=" << dim << std::endl;
+  deallog << "MappingCartesian: ";
+  const unsigned int      n_points = 5;
+  std::vector<Point<dim>> unit_points(Utilities::pow(n_points, dim));
+
+  switch (dim)
+    {
+      case 1:
+        for (unsigned int x = 0; x < n_points; ++x)
+          unit_points[x][0] = static_cast<double>(x) / n_points;
+        break;
+
+      case 2:
+        for (unsigned int x = 0; x < n_points; ++x)
+          for (unsigned int y = 0; y < n_points; ++y)
+            {
+              unit_points[y * n_points + x][0] =
+                static_cast<double>(x) / n_points;
+              unit_points[y * n_points + x][1] =
+                static_cast<double>(y) / n_points;
+            }
+        break;
+
+      case 3:
+        for (unsigned int x = 0; x < n_points; ++x)
+          for (unsigned int y = 0; y < n_points; ++y)
+            for (unsigned int z = 0; z < n_points; ++z)
+              {
+                unit_points[z * n_points * n_points + y * n_points + x][0] =
+                  static_cast<double>(x) / n_points;
+                unit_points[z * n_points * n_points + y * n_points + x][1] =
+                  static_cast<double>(y) / n_points;
+                unit_points[z * n_points * n_points + y * n_points + x][2] =
+                  static_cast<double>(z) / n_points;
+              }
+        break;
+    }
+
+  MappingCartesian<dim>                             mapping;
+  typename Triangulation<dim>::active_cell_iterator cell =
+    triangulation.begin_active();
+  std::vector<Point<dim>> real_points(unit_points.size());
+  for (unsigned int i = 0; i < unit_points.size(); ++i)
+    real_points[i] = mapping.transform_unit_to_real_cell(cell, unit_points[i]);
+  std::vector<Point<dim>> new_points(unit_points.size());
+  mapping.transform_points_real_to_unit_cell(cell, real_points, new_points);
+  for (unsigned int i = 0; i < unit_points.size(); ++i)
+    {
+      // for each of the points, verify that applying the forward map and
+      // then pull back get the same point again
+      AssertThrow(unit_points[i].distance(new_points[i]) < 1e-10,
+                  ExcInternalError());
+    }
+  deallog << "OK" << std::endl;
+}
+
+
+
+int
+main()
+{
+  initlog();
+
+  test<1>();
+  test<2>();
+  test<3>();
+}
diff --git a/tests/mappings/mapping_cartesian_points_real_to_unit.output b/tests/mappings/mapping_cartesian_points_real_to_unit.output
new file mode 100644
index 0000000000..cdd4ee5e92
--- /dev/null
+++ b/tests/mappings/mapping_cartesian_points_real_to_unit.output
@@ -0,0 +1,7 @@
+
+DEAL::dim=1
+DEAL::MappingCartesian: OK
+DEAL::dim=2
+DEAL::MappingCartesian: OK
+DEAL::dim=3
+DEAL::MappingCartesian: OK
-- 
2.39.5