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

◆ main()

int main	(	int	argc,
		char **	argv
	)
Definition at line 77 of file reduced_basis_ex1.C.
 {
   // Initialize libMesh.
   LibMeshInit init (argc, argv);
  
   // This example requires a linear solver package.
   libmesh_example_requires(libMesh::default_solver_package() != INVALID_SOLVER_PACKAGE,
                            "--enable-petsc, --enable-trilinos, or --enable-eigen");
  
 #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?  It works
   // with PETSc and Eigen sparse linear solvers though.
   libmesh_example_requires(libMesh::default_solver_package() != TRILINOS_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_ex1.in) using GetPot
   std::string parameters_filename = "reduced_basis_ex1.in";
   GetPot infile(parameters_filename);
  
   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
   GetPot command_line (argc, argv);
   int online_mode = 0;
   if (command_line.search(1, "-online_mode"))
     online_mode = command_line.next(online_mode);
  
   // 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());
  
   // 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::RBEvaluationSerialization rb_eval_writer(rb_con.get_rb_evaluation());
       rb_eval_writer.write_to_file("rb_eval.bin");
 #else
       rb_con.get_rb_evaluation().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);
         }
  
       // Basis functions should be orthonormal, so
       // print out the inner products to check this
       rb_con.print_basis_function_orthogonality();
     }
   else // Perform the Online stage of the RB method
     {
       // Read in the reduced basis data
 #if defined(LIBMESH_HAVE_CAPNPROTO)
       RBDataDeserialization::RBEvaluationDeserialization rb_eval_reader(rb_eval);
       rb_eval_reader.read_from_file("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
       rb_eval.rb_solve(online_N);
  
       // Print out outputs as well as the corresponding output error bounds.
       libMesh::out << "output 1, value = " << rb_eval.RB_outputs[0]
                    << ", bound = " << rb_eval.RB_output_error_bounds[0]
                    << std::endl;
       libMesh::out << "output 2, value = " << rb_eval.RB_outputs[1]
                    << ", bound = " << rb_eval.RB_output_error_bounds[1]
                    << std::endl;
       libMesh::out << "output 3, value = " << rb_eval.RB_outputs[2]
                    << ", bound = " << rb_eval.RB_output_error_bounds[2]
                    << std::endl;
       libMesh::out << "output 4, value = " << rb_eval.RB_outputs[3]
                    << ", bound = " << rb_eval.RB_output_error_bounds[3]
                    << std::endl << std::endl;
  
       if (store_basis_functions)
         {
           // Read in the basis functions
           rb_eval.read_in_basis_functions(rb_con);
  
           // Plot the solution
           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;
 }
Functions

Function Documentation

◆ main()
