From b01635937cda56f86906ff1c8a5bde0f66f78e0b Mon Sep 17 00:00:00 2001
From: Vladimir Yushutin <vyushut@clemson.edu>
Date: Thu, 9 Mar 2023 21:48:14 -0500
Subject: [PATCH] a test is added: make_flux_sparsity_pattern() is run with a
 face filter which outputs to deallog. This should happen exactly once for
 every face.

---
 .../flux_sparsity_pattern_visiting_once.cc    | 125 ++++++++++++++++++
 ...flux_sparsity_pattern_visiting_once.output |   4 +
 2 files changed, 129 insertions(+)
 create mode 100644 tests/sparsity/flux_sparsity_pattern_visiting_once.cc
 create mode 100644 tests/sparsity/flux_sparsity_pattern_visiting_once.output

diff --git a/tests/sparsity/flux_sparsity_pattern_visiting_once.cc b/tests/sparsity/flux_sparsity_pattern_visiting_once.cc
new file mode 100644
index 0000000000..31ebb6b460
--- /dev/null
+++ b/tests/sparsity/flux_sparsity_pattern_visiting_once.cc
@@ -0,0 +1,125 @@
+/* ---------------------------------------------------------------------
+ *
+ * Copyright (C) 2021 - 2022 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.
+ *
+ * ---------------------------------------------------------------------
+ */
+
+// @sect3{Include files}
+
+#include <deal.II/base/convergence_table.h>
+#include <deal.II/base/tensor.h>
+
+#include <deal.II/dofs/dof_tools.h>
+
+#include <deal.II/fe/fe_q.h>
+#include <deal.II/fe/fe_values.h>
+#include <deal.II/fe/mapping_q1.h>
+
+#include <deal.II/grid/filtered_iterator.h>
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/grid_out.h>
+#include <deal.II/grid/tria.h>
+
+#include <deal.II/lac/affine_constraints.h>
+#include <deal.II/lac/dynamic_sparsity_pattern.h>
+#include <deal.II/lac/solver_control.h>
+#include <deal.II/lac/sparse_direct.h>
+#include <deal.II/lac/sparsity_pattern.h>
+
+#include <deal.II/numerics/data_out.h>
+#include <deal.II/numerics/vector_tools.h>
+
+#include <fstream>
+
+#include "../tests.h"
+
+
+
+// @sect3{The main() function}
+// test that a face is visited once
+using namespace dealii;
+
+template <int dim>
+bool
+is_face_on_OY(const typename Triangulation<dim>::active_cell_iterator &cell,
+              const unsigned int face_index)
+{
+  bool on_OY = (std::abs(cell->face(face_index)->center()(0)) < 0.01);
+  deallog.get_file_stream()
+    << "This sentence should appear once when the corresponding face is visited only once"
+    << std::endl;
+  deallog.get_file_stream() << cell->index() << std::endl;
+  return on_OY;
+}
+
+template <int dim>
+void
+make_two_elements(Triangulation<dim> &triangulation)
+{
+  GridGenerator::hyper_cube(triangulation, -2.0, 2.0);
+  triangulation.begin_active()->set_refine_flag(
+    RefinementCase<dim>::cut_axis(0));
+  triangulation.execute_coarsening_and_refinement();
+}
+
+template <int dim>
+void
+create_flux_pattern_with_filter(DoFHandler<dim> &       dof_handler,
+                                DynamicSparsityPattern &dsp)
+{
+  Table<2, DoFTools::Coupling> cell_coupling(1, 1);
+  Table<2, DoFTools::Coupling> face_coupling(1, 1);
+  cell_coupling[0][0] = DoFTools::always;
+  face_coupling[0][0] = DoFTools::always;
+
+  const AffineConstraints<double> constraints;
+  const bool                      keep_constrained_dofs = true;
+
+  const auto face_has_flux_coupling = [&](const auto &       cell,
+                                          const unsigned int face_index) {
+    return is_face_on_OY<dim>(cell, face_index);
+  };
+
+  DoFTools::make_flux_sparsity_pattern(dof_handler,
+                                       dsp,
+                                       constraints,
+                                       keep_constrained_dofs,
+                                       cell_coupling,
+                                       face_coupling,
+                                       numbers::invalid_subdomain_id,
+                                       face_has_flux_coupling);
+}
+
+
+int
+main()
+{
+  initlog();
+  const int dim = 2;
+
+  // create a square with two elements
+  Triangulation<dim> triangulation;
+  make_two_elements(triangulation);
+
+  deallog << "dealii::Sparsity" << std::endl;
+  {
+    // Generate Q1 dofs for the mesh grid
+    DoFHandler<dim> dof_handler(triangulation);
+    const FE_Q<dim> finite_element(1);
+    dof_handler.distribute_dofs(finite_element);
+
+    // Compute the sparsity pattern specifying a face filter
+    DynamicSparsityPattern dsp(dof_handler.n_dofs(), dof_handler.n_dofs());
+    create_flux_pattern_with_filter(dof_handler, dsp);
+  }
+}
diff --git a/tests/sparsity/flux_sparsity_pattern_visiting_once.output b/tests/sparsity/flux_sparsity_pattern_visiting_once.output
new file mode 100644
index 0000000000..22c63b1009
--- /dev/null
+++ b/tests/sparsity/flux_sparsity_pattern_visiting_once.output
@@ -0,0 +1,4 @@
+
+DEAL::dealii::Sparsity
+This sentence should appear once when the corresponding face is visited only once
+1
-- 
2.39.5