Add new test for repartitioning of p:f:T

diff --git a/tests/fullydistributed_grids/repartitioning_09.cc b/tests/fullydistributed_grids/repartitioning_09.cc
new file mode 100644 (file)
index 0000000..0212370
--- /dev/null
+++ b/tests/fullydistributed_grids/repartitioning_09.cc
@@ -0,0 +1,167 @@
+// ------------------------------------------------------------------------
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// Copyright (C) 2025 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
+// TriangulationDescription::Utilities::create_description_from_triangulation()
+// with repartitioning capabilities (partition immersed mesh as the background
+// mesh).
+
+#include <deal.II/base/mpi_consensus_algorithms.h>
+
+#include <deal.II/distributed/fully_distributed_tria.h>
+#include <deal.II/distributed/repartitioning_policy_tools.h>
+#include <deal.II/distributed/tria.h>
+
+#include <deal.II/fe/fe_q.h>
+
+#include <deal.II/grid/grid_generator.h>
+#include <deal.II/grid/grid_out.h>
+#include <deal.II/grid/grid_tools.h>
+#include <deal.II/grid/tria_description.h>
+
+#include <deal.II/lac/la_parallel_vector.h>
+
+#include <deal.II/numerics/data_out.h>
+#include <deal.II/numerics/vector_tools.h>
+
+#include "../grid/tests.h"
+
+
+
+template <int dim, int spacedim = dim>
+class MyPolicy : public RepartitioningPolicyTools::Base<dim, spacedim>
+{
+public:
+  MyPolicy(const Triangulation<dim, spacedim> &tria_background)
+    : tria_background(tria_background)
+  {}
+
+  virtual LinearAlgebra::distributed::Vector<double>
+  partition(const Triangulation<dim, spacedim> &tria_immersed) const override
+  {
+    // 1) collect centers of immeresed mesh
+    std::vector<Point<spacedim>> points;
+
+    for (const auto &cell : tria_immersed.active_cell_iterators())
+      if (cell->is_locally_owned())
+        points.push_back(cell->center());
+
+    // 2) determine owner on background mesh
+    Utilities::MPI::RemotePointEvaluation<dim, spacedim> rpe;
+    Vector<double> ranks(tria_background.n_active_cells());
+    ranks =
+      Utilities::MPI::this_mpi_process(tria_background.get_communicator());
+
+    const auto point_ranks =
+      VectorTools::point_values<1>(mapping,
+                                   tria_background,
+                                   ranks,
+                                   points,
+                                   rpe,
+                                   VectorTools::EvaluationFlags::min);
+
+    const auto tria =
+      dynamic_cast<const parallel::TriangulationBase<dim, spacedim> *>(
+        &tria_immersed);
+
+    Assert(tria, ExcNotImplemented());
+
+    // 3) set partitioning
+    LinearAlgebra::distributed::Vector<double> partition(
+      tria->global_active_cell_index_partitioner().lock());
+
+    unsigned int counter = 0;
+    for (const auto &cell : tria_immersed.active_cell_iterators())
+      if (cell->is_locally_owned())
+        partition[cell->global_active_cell_index()] = point_ranks[counter++];
+
+    partition.update_ghost_values();
+
+    return partition;
+  }
+
+private:
+  const Triangulation<dim, spacedim> &tria_background;
+  const MappingQ1<dim, spacedim>      mapping; // TODO
+};
+
+
+template <int dim>
+void
+output_mesh(const Triangulation<dim> &tria_background, const std::string label)
+{
+  DataOut<dim> data_out_background;
+  data_out_background.attach_triangulation(tria_background);
+
+  Vector<double> ranks(tria_background.n_active_cells());
+  ranks = Utilities::MPI::this_mpi_process(tria_background.get_communicator());
+  data_out_background.add_data_vector(ranks, "ranks");
+  data_out_background.build_patches();
+  data_out_background.write_vtu_in_parallel(label,
+                                            tria_background.get_communicator());
+}
+
+
+template <int dim>
+void
+test()
+{
+  const MPI_Comm comm = MPI_COMM_WORLD;
+
+  // create background mesh
+  parallel::distributed::Triangulation<dim> tria_background(comm);
+  GridGenerator::hyper_cube(tria_background, -1, +1);
+  tria_background.refine_global(5);
+
+  // create immersed mesh (default partitioning)
+  parallel::distributed::Triangulation<dim> tria_immersed_old(comm);
+  GridGenerator::hyper_ball(tria_immersed_old, Point<dim>(0.1, 0.2), 0.5);
+  tria_immersed_old.refine_global(5);
+
+  // create immersed mesh with partitioning as in the case of the
+  // background mesh
+  MyPolicy<dim> policy_0(tria_background);
+  const auto    partition_0 = policy_0.partition(tria_immersed_old);
+
+  const auto construction_data =
+    TriangulationDescription::Utilities::create_description_from_triangulation(
+      tria_immersed_old, partition_0);
+
+  parallel::fullydistributed::Triangulation<dim> tria_immersed_new(comm);
+  for (const auto i : tria_immersed_old.get_manifold_ids())
+    if (i != numbers::flat_manifold_id)
+      tria_immersed_new.set_manifold(i, tria_immersed_old.get_manifold(i));
+
+  tria_immersed_new.create_triangulation(construction_data);
+
+  // output meshes
+  output_mesh(tria_background, "mesh_background.vtu");
+  output_mesh(tria_immersed_old, "mesh_immersed_old.vtu");
+  output_mesh(tria_immersed_new, "mesh_immersed_new.vtu");
+
+  // print statistics
+  print_statistics(tria_immersed_new);
+}
+
+
+
+int
+main(int argc, char **argv)
+{
+  Utilities::MPI::MPI_InitFinalize mpi(argc, argv, 1);
+  MPILogInitAll                    all;
+
+  test<2>();
+}

diff --git a/tests/fullydistributed_grids/repartitioning_09.with_p4est=true.mpirun=4.output b/tests/fullydistributed_grids/repartitioning_09.with_p4est=true.mpirun=4.output
new file mode 100644 (file)
index 0000000..c7c762a
--- /dev/null
+++ b/tests/fullydistributed_grids/repartitioning_09.with_p4est=true.mpirun=4.output
@@ -0,0 +1,27 @@
+
+DEAL:0::n_levels:                  6
+DEAL:0::n_cells:                   762
+DEAL:0::n_active_cells:            572
+DEAL:0::has_hanging_nodes:         false
+DEAL:0::
+
+DEAL:1::n_levels:                  6
+DEAL:1::n_cells:                   1222
+DEAL:1::n_active_cells:            917
+DEAL:1::has_hanging_nodes:         false
+DEAL:1::
+
+
+DEAL:2::n_levels:                  6
+DEAL:2::n_cells:                   2300
+DEAL:2::n_active_cells:            1726
+DEAL:2::has_hanging_nodes:         false
+DEAL:2::
+
+
+DEAL:3::n_levels:                  6
+DEAL:3::n_cells:                   3976
+DEAL:3::n_active_cells:            2983
+DEAL:3::has_hanging_nodes:         false
+DEAL:3::
+