Add test to check MatrixFree::reinit() works for multiple ranks and t…

…hreads

tests/matrix_free/reinit_matrix_free_threading.cc

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+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2023 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.
+//
+// ---------------------------------------------------------------------
+
+// Verify that MatrixFree::reinit() works without errors if run with
+// multithreadingf and multiple ranks.
+
+
+#include <deal.II/distributed/tria.h>
+
+#include <deal.II/fe/fe_dgq.h>
+#include <deal.II/fe/mapping_q1.h>
+
+#include <deal.II/grid/grid_generator.h>
+
+#include <deal.II/lac/affine_constraints.h>
+
+#include <deal.II/matrix_free/matrix_free.h>
+
+#include <iostream>
+
+#include "../tests.h"
+
+using namespace dealii;
+
+template <int dim, typename Number>
+void
+do_test(const unsigned int degree, const unsigned int n_refinements)
+{
+  deallog << "Create Triangulation with " << n_refinements << " refinements..."
+          << std::endl;
+  parallel::distributed::Triangulation<dim> tria(MPI_COMM_WORLD);
+  GridGenerator::hyper_cube(tria);
+  tria.refine_global(n_refinements);
+
+
+  deallog << "Create DoFHandler..." << std::endl;
+  DoFHandler<dim> dof_handler(tria);
+  dof_handler.distribute_dofs(FE_DGQ<dim>(degree));
+
+  deallog << "Setup AffineConstraints..." << std::endl;
+  AffineConstraints<Number> constraints;
+  constraints.close();
+
+  deallog << "Set MatrixFree AdditionalData..." << std::endl;
+  typename MatrixFree<dim, Number>::AdditionalData data;
+  data.mapping_update_flags_inner_faces = update_values;
+
+  deallog << "Reinit MatrixFree..." << std::endl;
+  MatrixFree<dim, Number> matrix_free;
+  matrix_free.reinit(
+    MappingQ1<dim>(), dof_handler, constraints, QGauss<dim>(degree + 1), data);
+
+  deallog << "OK" << std::endl << std::endl;
+}
+
+
+
+int
+main(int argc, char **argv)
+{
+  // Init with threading enabled
+  Utilities::MPI::MPI_InitFinalize mpi_init(argc, argv);
+  mpi_initlog();
+
+  do_test<2, double>(3, 3);
+  do_test<3, double>(2, 2);
+
+  deallog << std::endl;
+}

tests/matrix_free/reinit_matrix_free_threading.with_p4est=true.mpirun=2.output

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+
+DEAL::Create Triangulation with 3 refinements...
+DEAL::Create DoFHandler...
+DEAL::Setup AffineConstraints...
+DEAL::Set MatrixFree AdditionalData...
+DEAL::Reinit MatrixFree...
+DEAL::OK
+DEAL::
+DEAL::Create Triangulation with 3 refinements...
+DEAL::Create DoFHandler...
+DEAL::Setup AffineConstraints...
+DEAL::Set MatrixFree AdditionalData...
+DEAL::Reinit MatrixFree...
+DEAL::OK
+DEAL::
+DEAL::