Functions
int	main (int argc, char **argv)
Function Documentation

◆ main()

int main	(	int	argc,
		char **	argv
	)
Definition at line 54 of file reduced_basis_ex3.C.
 {
   // Initialize libMesh.
   LibMeshInit init (argc, argv);
 
   // This example requires SLEPc
 #if !defined(LIBMESH_HAVE_SLEPC)
   libmesh_example_requires(false, "--enable-slepc");
 #else
 
 #if !defined(LIBMESH_HAVE_XDR)
   // We need XDR support to write out reduced bases
   libmesh_example_requires(false, "--enable-xdr");
 #elif defined(LIBMESH_DEFAULT_SINGLE_PRECISION)
   // XDR binary support requires double precision
   libmesh_example_requires(false, "--disable-singleprecision");
 #endif
   // FIXME: This example currently segfaults with Trilinos?
   libmesh_example_requires(libMesh::default_solver_package() == PETSC_SOLVERS, "--enable-petsc");
 
   // Skip this 2D example if libMesh was compiled as 1D-only.
   libmesh_example_requires(2 <= LIBMESH_DIM, "2D support");
 
 #ifndef LIBMESH_ENABLE_DIRICHLET
   libmesh_example_requires(false, "--enable-dirichlet");
 #else
 
   // Parse the input file (reduced_basis_ex3.in) using GetPot
   std::string parameters_filename = "reduced_basis_ex3.in";
   GetPot infile(parameters_filename);
 
   // But allow the command line to override it.
   infile.parse_command_line(argc, argv);
 
   unsigned int n_elem = infile("n_elem", 1);       // Determines the number of elements in the "truth" mesh
   const unsigned int dim = 2;                      // The number of spatial dimensions
 
   bool store_basis_functions = infile("store_basis_functions", true); // Do we write the RB basis functions to disk?
 
   // Read the "online_mode" flag from the command line
   const int online_mode = libMesh::command_line_next("-online_mode", 0);
 
   // Build a mesh on the default MPI communicator.
   Mesh mesh (init.comm(), dim);
   MeshTools::Generation::build_square (mesh,
                                        n_elem, n_elem,
                                        0., 1.,
                                        0., 1.,
                                        QUAD4);
 
   // Create an equation systems object.
   EquationSystems equation_systems (mesh);
 
   // We override RBConstruction with SimpleRBConstruction in order to
   // specialize a few functions for this particular problem.
   SimpleRBConstruction & rb_con =
     equation_systems.add_system<SimpleRBConstruction> ("RBConvectionDiffusion");
 
 
   // Initialize the data structures for the equation system.
   equation_systems.init ();
 
   // Print out some information about the "truth" discretization
   equation_systems.print_info();
   mesh.print_info();
 
   // Build a new RBEvaluation object which will be used to perform
   // Reduced Basis calculations. This is required in both the
   // "Offline" and "Online" stages.
   SimpleRBEvaluation rb_eval(mesh.comm());
 
   // Finally, we need to give the RBConstruction object a pointer to
   // our RBEvaluation object
   rb_con.set_rb_evaluation(rb_eval);
 
   if (!online_mode) // Perform the Offline stage of the RB method
     {
       // Read in the data that defines this problem from the specified text file
       rb_con.process_parameters_file(parameters_filename);
 
       // Print out info that describes the current setup of rb_con
       rb_con.print_info();
 
       // Prepare rb_con for the Construction stage of the RB method.
       // This sets up the necessary data structures and performs
       // initial assembly of the "truth" affine expansion of the PDE.
       rb_con.initialize_rb_construction();
 
       // Compute the reduced basis space by computing "snapshots", i.e.
       // "truth" solves, at well-chosen parameter values and employing
       // these snapshots as basis functions.
       rb_con.train_reduced_basis();
 
       // Write out the data that will subsequently be required for the Evaluation stage
 #if defined(LIBMESH_HAVE_CAPNPROTO)
       RBDataSerialization::TransientRBEvaluationSerialization rb_eval_writer(rb_eval);
       rb_eval_writer.write_to_file("trans_rb_eval.bin");
 #else
       rb_eval.legacy_write_offline_data_to_files();
 #endif
 
       // If requested, write out the RB basis functions for visualization purposes
       if (store_basis_functions)
         {
           // Write out the basis functions
           rb_con.get_rb_evaluation().write_out_basis_functions(rb_con);
         }
     }
   else // Perform the Online stage of the RB method
     {
       // Read in the reduced basis data
 #if defined(LIBMESH_HAVE_CAPNPROTO)
       RBDataDeserialization::TransientRBEvaluationDeserialization rb_eval_reader(rb_eval);
       rb_eval_reader.read_from_file("trans_rb_eval.bin", /*read_error_bound_data*/ true);
 #else
       rb_eval.legacy_read_offline_data_from_files();
 #endif
 
       // Read in online_N and initialize online parameters
       unsigned int online_N = infile("online_N", 1);
       Real online_x_vel = infile("online_x_vel", 0.);
       Real online_y_vel = infile("online_y_vel", 0.);
       RBParameters online_mu;
       online_mu.set_value("x_vel", online_x_vel);
       online_mu.set_value("y_vel", online_y_vel);
       rb_eval.set_parameters(online_mu);
       rb_eval.print_parameters();
 
       // Now do the Online solve using the precomputed reduced basis
       Real error_bound_final_time = rb_eval.rb_solve(online_N);
 
       libMesh::out << "Error bound (absolute) at the final time is "
                    << error_bound_final_time << std::endl << std::endl;
 
       if (store_basis_functions)
         {
           // Read in the basis functions
           rb_eval.read_in_basis_functions(rb_con);
 
           // Plot the solution at the final time level
           rb_con.pull_temporal_discretization_data(rb_eval);
           rb_con.set_time_step(rb_con.get_n_time_steps());
           rb_con.load_rb_solution();
 #ifdef LIBMESH_HAVE_EXODUS_API
           ExodusII_IO(mesh).write_equation_systems ("RB_sol.e", equation_systems);
 #endif
 
           // Plot the first basis function that was generated from the train_reduced_basis
           // call in the Offline stage
           rb_con.load_basis_function(0);
 #ifdef LIBMESH_HAVE_EXODUS_API
           ExodusII_IO(mesh).write_equation_systems ("bf0.e", equation_systems);
 #endif
         }
     }
 
 #endif // LIBMESH_ENABLE_DIRICHLET
 
   return 0;
 
 #endif // LIBMESH_HAVE_SLEPC
 }
Functions

Function Documentation

◆ main()
