From cc49a0467b83f2dcca82e8c4a76f204cb72310df Mon Sep 17 00:00:00 2001
From: Jiaqi Zhang <jiaqi2@clemson.edu>
Date: Sun, 19 Jun 2022 23:04:04 -0400
Subject: [PATCH] clear user constraints

---
 .../deal.II/multigrid/mg_constrained_dofs.h   |  16 +++
 tests/multigrid/constrained_dofs_07.cc        | 101 ++++++++++++++++++
 tests/multigrid/constrained_dofs_07.output    |  11 ++
 3 files changed, 128 insertions(+)
 create mode 100644 tests/multigrid/constrained_dofs_07.cc
 create mode 100644 tests/multigrid/constrained_dofs_07.output

diff --git a/include/deal.II/multigrid/mg_constrained_dofs.h b/include/deal.II/multigrid/mg_constrained_dofs.h
index 1b8304a1e3..64694b461c 100644
--- a/include/deal.II/multigrid/mg_constrained_dofs.h
+++ b/include/deal.II/multigrid/mg_constrained_dofs.h
@@ -145,6 +145,12 @@ public:
                                   const types::boundary_id         bid,
                                   const unsigned int first_vector_component);
 
+  /**
+   * Clear the user constraints on all levels.
+   */
+  void
+  clear_user_constraints();
+
   /**
    * Reset the data structures.
    */
@@ -459,6 +465,16 @@ MGConstrainedDoFs::add_user_constraints(
 }
 
 
+
+inline void
+MGConstrainedDoFs::clear_user_constraints()
+{
+  for (auto &constraint : user_constraints)
+    constraint.clear();
+}
+
+
+
 inline void
 MGConstrainedDoFs::clear()
 {
diff --git a/tests/multigrid/constrained_dofs_07.cc b/tests/multigrid/constrained_dofs_07.cc
new file mode 100644
index 0000000000..9f543778cc
--- /dev/null
+++ b/tests/multigrid/constrained_dofs_07.cc
@@ -0,0 +1,101 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2016 - 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.
+//
+// ---------------------------------------------------------------------
+
+
+// Check clear_user_constraints()
+#include <deal.II/distributed/tria.h>
+
+#include <deal.II/fe/fe_q.h>
+
+#include <deal.II/grid/grid_generator.h>
+
+#include <deal.II/lac/la_parallel_vector.h>
+
+#include <deal.II/multigrid/mg_transfer.h>
+#include <deal.II/multigrid/mg_transfer_matrix_free.h>
+
+#include "../tests.h"
+
+template <int dim>
+void
+check()
+{
+  Triangulation<dim> tr(Triangulation<dim>::limit_level_difference_at_vertices);
+  GridGenerator::hyper_cube(tr, 0, 1, false);
+
+  typename Triangulation<dim>::active_cell_iterator cell = tr.begin_active();
+  cell->face(0)->set_all_boundary_ids(1);
+
+  tr.refine_global(1);
+
+  FE_Q<dim> fe = FE_Q<dim>(1);
+
+  DoFHandler<dim> mgdof(tr);
+  mgdof.distribute_dofs(fe);
+  mgdof.distribute_mg_dofs();
+
+  MGConstrainedDoFs mg_constrained_dofs;
+  mg_constrained_dofs.initialize(mgdof);
+
+  for (unsigned int level = 0; level < tr.n_levels(); ++level)
+    {
+      IndexSet relevant_dofs;
+      DoFTools::extract_locally_relevant_level_dofs(mgdof,
+                                                    level,
+                                                    relevant_dofs);
+      AffineConstraints<double> level_constraints;
+      level_constraints.reinit(relevant_dofs);
+
+      typename DoFHandler<dim>::level_face_iterator face0 =
+        mgdof.begin(level)->face(0);
+      std::vector<types::global_dof_index> face_dofs(fe.dofs_per_face);
+      face0->get_mg_dof_indices(level, face_dofs);
+      for (unsigned int i = 0; i < face_dofs.size(); ++i)
+        {
+          if (level_constraints.can_store_line(face_dofs[i]))
+            {
+              level_constraints.add_line(face_dofs[i]);
+              level_constraints.set_inhomogeneity(face_dofs[i], 5.0);
+            }
+        }
+      level_constraints.close();
+      mg_constrained_dofs.add_user_constraints(level, level_constraints);
+      deallog << " level: " << level
+              << " n_constraints: " << level_constraints.n_constraints()
+              << std::endl;
+    }
+
+  mg_constrained_dofs.clear_user_constraints();
+  for (unsigned int level = 0; level < tr.n_levels(); ++level)
+    {
+      const AffineConstraints<double> &level_constraints =
+        mg_constrained_dofs.get_user_constraint_matrix(level);
+      deallog << " level: " << level
+              << " n_constraints: " << level_constraints.n_constraints()
+              << std::endl;
+    }
+}
+
+
+int
+main()
+{
+  initlog();
+
+  check<2>();
+  deallog << std::endl;
+  check<3>();
+  deallog << std::endl;
+}
diff --git a/tests/multigrid/constrained_dofs_07.output b/tests/multigrid/constrained_dofs_07.output
new file mode 100644
index 0000000000..a42fd4ab0f
--- /dev/null
+++ b/tests/multigrid/constrained_dofs_07.output
@@ -0,0 +1,11 @@
+
+DEAL:: level: 0 n_constraints: 2
+DEAL:: level: 1 n_constraints: 2
+DEAL:: level: 0 n_constraints: 0
+DEAL:: level: 1 n_constraints: 0
+DEAL::
+DEAL:: level: 0 n_constraints: 4
+DEAL:: level: 1 n_constraints: 4
+DEAL:: level: 0 n_constraints: 0
+DEAL:: level: 1 n_constraints: 0
+DEAL::
-- 
2.39.5