Add another testcase for make_consistent_in_parallel().

diff --git a/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.cc b/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.cc
new file mode 100644 (file)
index 0000000..3970016
--- /dev/null
+++ b/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.cc
@@ -0,0 +1,71 @@
+// ------------------------------------------------------------------------
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// Copyright (C) 2018 - 2023 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.
+//
+// ------------------------------------------------------------------------
+
+
+
+// Test AffineConstraints<double>::make_consistent_in_parallel for a
+// case where each process owns one DoF and on each process p>0 we
+// know about one constraint that constrains X_p=0.5*X_{p-1}. After making
+// things consistent in parallel, this needs to all reduce to X_p=factor*X1.
+//
+// Compared to the plain _05 test, this variation has the same
+// constraints except that the constraint is not added by the process
+// that *owns* the DoF, but by another process that only has this DoF
+// among its locally relevant ones.
+
+#include <deal.II/base/mpi.h>
+
+#include <deal.II/lac/affine_constraints.h>
+
+#include "../tests.h"
+
+int
+main(int argc, char **argv)
+{
+  Utilities::MPI::MPI_InitFinalize mpi_init(argc, argv);
+  MPILogInitAll                    all;
+
+  const unsigned int my_proc = Utilities::MPI::this_mpi_process(MPI_COMM_WORLD);
+  const unsigned int n_procs = Utilities::MPI::n_mpi_processes(MPI_COMM_WORLD);
+
+  // Process N only owns DoF N:
+  const unsigned int n_indices = n_procs;
+  IndexSet           owned_elements(n_indices);
+  owned_elements.add_index(my_proc);
+
+  // Process N has N, N+1 and N-1 as its locally relevant DoFs:
+  IndexSet relevant_elements(n_indices);
+  relevant_elements.add_index(my_proc);
+  if (my_proc > 0)
+    relevant_elements.add_index(my_proc - 1);
+  if (my_proc != n_procs - 1)
+    relevant_elements.add_index(my_proc + 1);
+  AffineConstraints<double> constraints(owned_elements, relevant_elements);
+
+  // Let each process add a constraint for a DoF that it doesn't own:
+  if (my_proc != n_procs - 1)
+    constraints.add_constraint(my_proc + 1, {{my_proc, 0.5}});
+
+  deallog << "Constraints as created:" << std::endl;
+  constraints.print(deallog.get_file_stream());
+
+  constraints.make_consistent_in_parallel(owned_elements,
+                                          relevant_elements,
+                                          MPI_COMM_WORLD);
+
+  deallog << "Constraints as made consistent:" << std::endl;
+  constraints.print(deallog.get_file_stream());
+
+  return 0;
+}

diff --git a/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.mpirun=5.output b/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.mpirun=5.output
new file mode 100644 (file)
index 0000000..21da6c3
--- /dev/null
+++ b/tests/lac/constraints_make_consistent_in_parallel_05_nonowning.mpirun=5.output
@@ -0,0 +1,37 @@
+
+DEAL:0::Constraints as created:
+    1 0:  0.500000
+DEAL:0::Constraints as made consistent:
+    1 0:  0.500000
+
+DEAL:1::Constraints as created:
+    2 1:  0.500000
+DEAL:1::Constraints as made consistent:
+    1 0:  0.500000
+    2 0:  0.250000
+
+
+DEAL:2::Constraints as created:
+    3 2:  0.500000
+DEAL:2::Constraints as made consistent:
+    1 0:  0.500000
+    2 0:  0.250000
+    3 0:  0.125000
+
+
+DEAL:3::Constraints as created:
+    4 3:  0.500000
+DEAL:3::Constraints as made consistent:
+    1 0:  0.500000
+    2 0:  0.250000
+    3 0:  0.125000
+    4 0:  0.0625000
+
+
+DEAL:4::Constraints as created:
+DEAL:4::Constraints as made consistent:
+    1 0:  0.500000
+    2 0:  0.250000
+    3 0:  0.125000
+    4 0:  0.0625000
+