--- /dev/null
+//---------------------------------------------------------------------------
+// $Id$
+// Version: $Name$
+//
+// Copyright (C) 2009, 2010, 2011 by the deal.II authors
+//
+// This file is subject to QPL and may not be distributed
+// without copyright and license information. Please refer
+// to the file deal.II/doc/license.html for the text and
+// further information on this license.
+//
+//---------------------------------------------------------------------------
+
+
+// Test VectorTools::integrate_difference for parallel computations.
+
+#include "../tests.h"
+#include "coarse_grid_common.h"
+#include <base/logstream.h>
+#include <base/function.h>
+#include <base/tensor.h>
+#include <lac/trilinos_vector.h>
+#include <grid/tria.h>
+#include <grid/grid_generator.h>
+#include <distributed/tria.h>
+#include <grid/grid_generator.h>
+#include <grid/grid_out.h>
+#include <dofs/dof_handler.h>
+#include <dofs/dof_handler.h>
+#include <dofs/dof_tools.h>
+#include <grid/tria_accessor.h>
+#include <grid/tria_iterator.h>
+#include <dofs/dof_accessor.h>
+
+#include <fe/fe_q.h>
+#include <numerics/vectors.h>
+
+#include <fstream>
+
+
+template <int dim>
+class LinearFunction : public Function<dim>
+{
+ public:
+ double value (const Point<dim> &p,
+ const unsigned int) const
+ {
+ return p[0];
+ }
+};
+
+
+template<int dim>
+void test()
+{
+ parallel::distributed::Triangulation<dim> tr(MPI_COMM_WORLD);
+
+ GridGenerator::hyper_cube(tr);
+ tr.refine_global (2);
+
+ const FE_Q<dim> fe(2);
+ DoFHandler<dim> dofh(tr);
+ dofh.distribute_dofs (fe);
+
+ TrilinosWrappers::MPI::Vector interpolated(dofh.locally_owned_dofs(),
+ MPI_COMM_WORLD);
+ VectorTools::interpolate (dofh,
+ LinearFunction<dim>(),
+ interpolated);
+
+ IndexSet relevant_set;
+ DoFTools::extract_locally_relevant_dofs (dofh, relevant_set);
+ TrilinosWrappers::MPI::Vector x_rel(relevant_set, MPI_COMM_WORLD);
+ x_rel = interpolated;
+
+ // integrate the difference between the
+ // linear function above and the zero
+ // function. for this case, we can
+ // compute the exact values by hand. the
+ // ones printed in the output are correct
+ Vector<float> results (tr.n_active_cells());
+ VectorTools::integrate_difference (dofh, x_rel,
+ ZeroFunction<dim>(),
+ results,
+ QGauss<dim>(3),
+ VectorTools::L2_norm);
+ double local = results.l2_norm() * results.l2_norm();
+ double global;
+
+ MPI_Allreduce (&local, &global, 1, MPI_DOUBLE,
+ MPI_SUM,
+ tr.get_communicator());
+
+ if (Utilities::System::get_this_mpi_process (MPI_COMM_WORLD) == 0)
+ deallog << "difference = " << std::sqrt(global)
+ << std::endl;
+
+ // we have f(\vec x)=x, so the difference
+ // squared is \int f(x)^2 = 1/3 and the
+ // norm is 1/sqrt(3)
+ //
+ // note that we have used a quadrature
+ // formula of sufficient order to get exact
+ // results
+ Assert (std::fabs(std::sqrt(global) - 1./std::sqrt(3.)) < 1e-6,
+ ExcInternalError());
+}
+
+
+int main(int argc, char *argv[])
+{
+#ifdef DEAL_II_COMPILER_SUPPORTS_MPI
+ MPI_Init (&argc,&argv);
+#else
+ (void)argc;
+ (void)argv;
+#endif
+
+ unsigned int myid = Utilities::System::get_this_mpi_process (MPI_COMM_WORLD);
+
+
+ deallog.push(Utilities::int_to_string(myid));
+
+ if (myid == 0)
+ {
+ std::ofstream logfile(output_file_for_mpi("integrate_difference").c_str());
+ deallog.attach(logfile);
+ deallog.depth_console(0);
+ deallog.threshold_double(1.e-10);
+
+ deallog.push("2d");
+ test<2>();
+ deallog.pop();
+
+ deallog.push("3d");
+ test<3>();
+ deallog.pop();
+ }
+ else
+ {
+ deallog.push("2d");
+ test<2>();
+ deallog.pop();
+
+ deallog.push("3d");
+ test<3>();
+ deallog.pop();
+ }
+
+#ifdef DEAL_II_COMPILER_SUPPORTS_MPI
+ MPI_Finalize();
+#endif
+}