Communicate refinement flags in p:s:T

diff --git a/doc/news/changes/minor/20220712Munch b/doc/news/changes/minor/20220712Munch
new file mode 100644 (file)
index 0000000..f2dd59e
--- /dev/null
+++ b/doc/news/changes/minor/20220712Munch
@@ -0,0 +1,4 @@
+Improved: Refinement and coarsening flags are now
+communicated in parallel::shared::Triangulation.
+<br>
+(Peter Munch, 2022/07/12)

diff --git a/include/deal.II/distributed/shared_tria.h b/include/deal.II/distributed/shared_tria.h
index 102c07ac6546507db8e109aa6ffa58595395435e..65128423902bd301c7015ef6a2f9bc7e31fb3b5d 100644 (file)
--- a/include/deal.II/distributed/shared_tria.h
+++ b/include/deal.II/distributed/shared_tria.h
@@ -69,10 +69,9 @@ namespace parallel
      * about cells owned by other processors with the exception of a single
      * layer of ghost cells around their own part of the domain.
      *
-     * As a consequence of storing the entire mesh on each processor, active
-     * cells need to be flagged for refinement or coarsening consistently on
-     * all processors if you want to adapt them, regardless of being classified
-     * as locally owned, ghost or artificial.
+     * Active cells need to be flagged for refinement or coarsening
+     * locally owned cells. The relevant information is gathered for
+     * ghost and artificial cells internally via MPI communication.
      *
      * The class is also useful in cases where compute time and memory
      * considerations dictate that the program needs to be run in parallel,

diff --git a/source/distributed/shared_tria.cc b/source/distributed/shared_tria.cc
index deb132b1fe3cfc67a6c4716d12a0bf36fea646ff..f9b999d28f73860016d3a0f0da2ecb09506105bf 100644 (file)
--- a/source/distributed/shared_tria.cc
+++ b/source/distributed/shared_tria.cc
@@ -351,6 +351,51 @@ namespace parallel
     void
     Triangulation<dim, spacedim>::execute_coarsening_and_refinement()
     {
+      // make sure that all refinement/coarsening flags are the same on all
+      // processes
+      {
+        std::vector<unsigned int> refinement_configurations(
+          this->n_active_cells() * 2, 0u);
+        for (const auto &cell : this->active_cell_iterators())
+          if (cell->is_locally_owned())
+            {
+              refinement_configurations[cell->active_cell_index() * 2 + 0] =
+                cell->refine_flag_set();
+              refinement_configurations[cell->active_cell_index() * 2 + 1] =
+                cell->coarsen_flag_set();
+            }
+
+        Utilities::MPI::max(refinement_configurations,
+                            this->get_communicator(),
+                            refinement_configurations);
+
+        for (const auto &cell : this->active_cell_iterators())
+          {
+            cell->clear_refine_flag();
+            cell->clear_coarsen_flag();
+
+            Assert(
+              (refinement_configurations[cell->active_cell_index() * 2 + 0] >
+                   0 ?
+                 1 :
+                 0) +
+                  refinement_configurations[cell->active_cell_index() * 2 +
+                                            1] <=
+                1,
+              ExcMessage(
+                "Refinement/coarsening flags of cells are not consistent in parallel!"));
+
+            if (refinement_configurations[cell->active_cell_index() * 2 + 0] >
+                0)
+              cell->set_refine_flag(RefinementCase<dim>(
+                refinement_configurations[cell->active_cell_index() * 2 + 0]));
+
+            if (refinement_configurations[cell->active_cell_index() * 2 + 1] >
+                0)
+              cell->set_coarsen_flag();
+          }
+      }
+
       dealii::Triangulation<dim, spacedim>::execute_coarsening_and_refinement();
       partition();
       this->update_number_cache();

diff --git a/tests/sharedtria/refine_and_coarsen_02.cc b/tests/sharedtria/refine_and_coarsen_02.cc
new file mode 100644 (file)
index 0000000..a42d545
--- /dev/null
+++ b/tests/sharedtria/refine_and_coarsen_02.cc
@@ -0,0 +1,88 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 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.
+//
+// ---------------------------------------------------------------------
+
+
+
+// test that coarsening/refinement flags are communicated correctly
+
+#include <deal.II/distributed/shared_tria.h>
+
+#include <deal.II/grid/grid_generator.h>
+
+#include "../tests.h"
+
+
+template <int dim>
+void
+test()
+{
+  using Number              = double;
+  using VectorizedArrayType = VectorizedArray<Number>;
+
+  parallel::shared::Triangulation<dim> tria(
+    MPI_COMM_WORLD,
+    ::Triangulation<dim>::none,
+    true,
+    parallel::shared::Triangulation<dim>::partition_custom_signal);
+
+  tria.signals.create.connect([&]() {
+    for (const auto &cell : tria.active_cell_iterators())
+      if (cell->center()[1] < 0.5)
+        cell->set_subdomain_id(0);
+      else
+        cell->set_subdomain_id(1);
+  });
+
+  const auto print = [&]() {
+    for (unsigned int l = 0; l < tria.n_levels(); ++l)
+      deallog << tria.n_cells(l) << " ";
+    deallog << std::endl;
+  };
+
+  GridGenerator::hyper_cube(tria);
+
+  print();
+
+  tria.refine_global();
+
+  print();
+
+  for (const auto &cell : tria.active_cell_iterators())
+    if (cell->is_locally_owned())
+      {
+        const auto center = cell->center();
+
+        if (center[0] < 0.5 && center[1] < 0.5)
+          cell->set_refine_flag();
+        else if (center[0] > 0.5 && center[1] > 0.5)
+          cell->set_coarsen_flag();
+      }
+
+  tria.execute_coarsening_and_refinement();
+
+  print();
+}
+
+
+main(int argc, char **argv)
+{
+  Utilities::MPI::MPI_InitFinalize mpi_initialization(argc, argv, 1);
+
+  MPILogInitAll log;
+
+  AssertDimension(Utilities::MPI::n_mpi_processes(MPI_COMM_WORLD), 2);
+
+  test<2>();
+}

diff --git a/tests/sharedtria/refine_and_coarsen_02.mpirun=2.output b/tests/sharedtria/refine_and_coarsen_02.mpirun=2.output
new file mode 100644 (file)
index 0000000..7b87127
--- /dev/null
+++ b/tests/sharedtria/refine_and_coarsen_02.mpirun=2.output
@@ -0,0 +1,9 @@
+
+DEAL:0::1 
+DEAL:0::1 4 
+DEAL:0::1 4 4 
+
+DEAL:1::1 
+DEAL:1::1 4 
+DEAL:1::1 4 4 
+