From fe006402cf3d60ded068cf88aaa72402263a72f3 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Tue, 25 Apr 2023 13:33:02 -0600
Subject: [PATCH] Add a test.

---
 tests/feinterface/fe_interface_values_14.cc   | 125 ++++++++++++++++++
 .../feinterface/fe_interface_values_14.output |   7 +
 2 files changed, 132 insertions(+)
 create mode 100644 tests/feinterface/fe_interface_values_14.cc
 create mode 100644 tests/feinterface/fe_interface_values_14.output

diff --git a/tests/feinterface/fe_interface_values_14.cc b/tests/feinterface/fe_interface_values_14.cc
new file mode 100644
index 0000000000..07c006afe7
--- /dev/null
+++ b/tests/feinterface/fe_interface_values_14.cc
@@ -0,0 +1,125 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2018 - 2021 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.
+//
+// ---------------------------------------------------------------------
+
+
+// Set up a two cells with different elements, such that neither element
+// dominates. Create an FEInterfaceValues object and call reinit on it.
+//
+// In this test case, there is only one quadrature and mapping, so
+// that is the only reasonable choice.
+
+#include <deal.II/base/quadrature_lib.h>
+
+#include <deal.II/fe/fe_interface_values.h>
+#include <deal.II/fe/fe_q.h>
+#include <deal.II/fe/fe_system.h>
+
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/tria.h>
+
+#include "../tests.h"
+
+template <int dim>
+void
+make_2_cells(Triangulation<dim> &tria);
+
+template <>
+void
+make_2_cells<2>(Triangulation<2> &tria)
+{
+  const unsigned int        dim         = 2;
+  std::vector<unsigned int> repetitions = {2, 1};
+  Point<dim>                p1;
+  Point<dim>                p2(2.0, 1.0);
+
+  GridGenerator::subdivided_hyper_rectangle(tria, repetitions, p1, p2);
+}
+
+
+template <int dim>
+void
+test()
+{
+  Triangulation<dim> tria;
+  make_2_cells(tria);
+
+  const unsigned      max_fe_degree = 2;
+  const FESystem<dim> fe_left(FE_Q<dim>(1), FE_Q<dim>(2));
+  const FESystem<dim> fe_right(FE_Q<dim>(2), FE_Q<dim>(1));
+
+  hp::FECollection<dim> fe_collection;
+  fe_collection.push_back(fe_left);
+  fe_collection.push_back(fe_right);
+
+  DoFHandler<dim> dofh(tria);
+
+  const unsigned int face_index = 1;
+
+  auto cell     = dofh.begin();
+  auto neighbor = cell->neighbor(face_index);
+
+  cell->set_active_fe_index(0);
+  neighbor->set_active_fe_index(1);
+
+  dofh.distribute_dofs(fe_collection);
+
+  const QGauss<dim - 1>          quadrature(max_fe_degree + 1);
+  const hp::QCollection<dim - 1> q_collection(quadrature);
+
+  const MappingQ<dim>              mapping(1);
+  const hp::MappingCollection<dim> mapping_collection(mapping);
+
+
+  deallog << "Adjacent finite elements: " << cell->get_fe().get_name()
+          << " and " << neighbor->get_fe().get_name() << std::endl;
+
+  const UpdateFlags      update_flags = update_values;
+  FEInterfaceValues<dim> fiv(mapping_collection,
+                             fe_collection,
+                             q_collection,
+                             update_flags);
+  fiv.reinit(cell,
+             face_index,
+             /* subface_no */ numbers::invalid_unsigned_int,
+             neighbor,
+             cell->neighbor_of_neighbor(face_index),
+             /* subface_no_neighbor */ numbers::invalid_unsigned_int,
+             /* q_index */ numbers::invalid_unsigned_int,
+             /* mapping_index */ numbers::invalid_unsigned_int,
+             /* fe_index */ numbers::invalid_unsigned_int);
+
+  deallog << "Chosen quadrature for the common face has "
+          << fiv.get_fe_face_values(0).get_quadrature().size()
+          << " quadrature points. These points are located at:" << std::endl;
+  for (const auto p : fiv.get_fe_face_values(0).get_quadrature().get_points())
+    deallog << "  " << p << std::endl;
+
+  // Also check that we see the same quadrature formula from both
+  // sides:
+  Assert(fiv.get_fe_face_values(0).get_quadrature().get_points() ==
+           fiv.get_fe_face_values(1).get_quadrature().get_points(),
+         ExcInternalError());
+
+  deallog << "OK" << std::endl;
+}
+
+
+
+int
+main()
+{
+  initlog();
+  test<2>();
+}
diff --git a/tests/feinterface/fe_interface_values_14.output b/tests/feinterface/fe_interface_values_14.output
new file mode 100644
index 0000000000..f3c0a20f22
--- /dev/null
+++ b/tests/feinterface/fe_interface_values_14.output
@@ -0,0 +1,7 @@
+
+DEAL::Adjacent finite elements: FESystem<2>[FE_Q<2>(1)-FE_Q<2>(2)] and FESystem<2>[FE_Q<2>(2)-FE_Q<2>(1)]
+DEAL::Chosen quadrature for the common face has 3 quadrature points. These points are located at:
+DEAL::  0.112702
+DEAL::  0.500000
+DEAL::  0.887298
+DEAL::OK
-- 
2.39.5