From: Denis Davydov Date: Tue, 9 Aug 2016 14:08:43 +0000 (+0200) Subject: GMG: add MGCoarseGridPreconditioner to apply a few steps of smoother at the coarse... X-Git-Tag: v8.5.0-rc1~785^2~3 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=052e09c75767ee2dd8880186e97dcd7bd6a9fa7a;p=dealii.git GMG: add MGCoarseGridPreconditioner to apply a few steps of smoother at the coarse level --- diff --git a/include/deal.II/multigrid/mg_coarse.h b/include/deal.II/multigrid/mg_coarse.h index db6b57a2bd..b4cff26a1c 100644 --- a/include/deal.II/multigrid/mg_coarse.h +++ b/include/deal.II/multigrid/mg_coarse.h @@ -27,6 +27,47 @@ DEAL_II_NAMESPACE_OPEN /*!@addtogroup mg */ /*@{*/ +/** + * Coarse grid solver using preconditioners only. This is a little wrapper, + * transforming a preconditioner into + * a coarse grid solver. + * + * @author Denis Davydov, 2016. + */ +template > +class MGCoarseGridApplySmoother : public MGCoarseGridBase +{ +public: + /** + * Default constructor. + */ + MGCoarseGridApplySmoother (); + + /** + * Constructor. Store preconditioner for later use. + */ + MGCoarseGridApplySmoother (const MGSmootherBase &coarse_smooth); + + /** + * Initialize new data. + */ + void initialize (const MGSmootherBase &coarse_smooth); + + /** + * Implementation of the abstract function. + */ + void operator() (const unsigned int level, + VectorType &dst, + const VectorType &src) const; + +private: + /** + * Reference to the preconditioner. + */ + SmartPointer,Multigrid > coarse_smooth; +}; + + /** * Coarse grid solver using LAC iterative methods. This is a little wrapper, * transforming a triplet of iterative solver, matrix and preconditioner into @@ -185,6 +226,39 @@ private: /*@}*/ #ifndef DOXYGEN +/* ------------------ Functions for MGCoarseGridApplySmoother -----------*/ +template +MGCoarseGridApplySmoother::MGCoarseGridApplySmoother () + : coarse_smooth(NULL) +{ +} + +template +MGCoarseGridApplySmoother::MGCoarseGridApplySmoother (const MGSmootherBase &coarse_smooth) + : coarse_smooth(NULL) +{ + initialize(coarse_smooth); +} + + +template +void +MGCoarseGridApplySmoother::initialize (const MGSmootherBase &coarse_smooth_) +{ + coarse_smooth = + SmartPointer,Multigrid > + (&coarse_smooth_,typeid(*this).name()); +} + +template +void +MGCoarseGridApplySmoother::operator() (const unsigned int level, + VectorType &dst, + const VectorType &src) const +{ + coarse_smooth->smooth(level, dst, src); +} + /* ------------------ Functions for MGCoarseGridLACIteration ------------ */ diff --git a/tests/multigrid/step-16-50-mpi-smoother.cc b/tests/multigrid/step-16-50-mpi-smoother.cc new file mode 100644 index 0000000000..71544b62e9 --- /dev/null +++ b/tests/multigrid/step-16-50-mpi-smoother.cc @@ -0,0 +1,581 @@ +/* --------------------------------------------------------------------- + * + * Copyright (C) 2016 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 at + * the top level of the deal.II distribution. + * + * --------------------------------------------------------------------- + */ + +// Same as step-16-50, but use Jacobi smoother at the coarsest grid via MGCoarseGridApplySmoother. +// In this particular case, the number of iterations untill convergence is +// exactly the same as for MGCoarseGridLACIteration. + +#include "../tests.h" + +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include +#include + +#include +#include +#include + +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + + +#include + + +namespace LA +{ +#ifdef USE_PETSC_LA + using namespace dealii::LinearAlgebraPETSc; +#else + using namespace dealii::LinearAlgebraTrilinos; +#endif +} + +#include +#include +#include + +namespace Step50 +{ + using namespace dealii; + + + + template + class LaplaceProblem + { + public: + LaplaceProblem (const unsigned int deg); + void run (); + + private: + void setup_system (); + void assemble_system (); + void assemble_multigrid (); + void solve (); + void refine_grid (); + + parallel::distributed::Triangulation triangulation; + FE_Q fe; + DoFHandler mg_dof_handler; + + typedef LA::MPI::SparseMatrix matrix_t; + typedef LA::MPI::Vector vector_t; + + matrix_t system_matrix; + + IndexSet locally_relevant_set; + + ConstraintMatrix hanging_node_constraints; + ConstraintMatrix constraints; + + vector_t solution; + vector_t system_rhs; + + const unsigned int degree; + + MGLevelObject mg_matrices; + MGLevelObject mg_interface_matrices; + MGConstrainedDoFs mg_constrained_dofs; + }; + + + + + + template + class Coefficient : public Function + { + public: + Coefficient () : Function() {} + + virtual double value (const Point &p, + const unsigned int component = 0) const; + + virtual void value_list (const std::vector > &points, + std::vector &values, + const unsigned int component = 0) const; + }; + + + + template + double Coefficient::value (const Point &p, + const unsigned int) const + { + if (p.square() < 0.5*0.5) + return 5; + else + return 1; + } + + + + template + void Coefficient::value_list (const std::vector > &points, + std::vector &values, + const unsigned int component) const + { + const unsigned int n_points = points.size(); + + Assert (values.size() == n_points, + ExcDimensionMismatch (values.size(), n_points)); + + Assert (component == 0, + ExcIndexRange (component, 0, 1)); + + for (unsigned int i=0; i::value (points[i]); + } + + + + + template + LaplaceProblem::LaplaceProblem (const unsigned int degree) + : + triangulation (MPI_COMM_WORLD,Triangulation:: + limit_level_difference_at_vertices, + parallel::distributed::Triangulation::construct_multigrid_hierarchy), + fe (degree), + mg_dof_handler (triangulation), + degree(degree) + {} + + + + template + void LaplaceProblem::setup_system () + { + mg_dof_handler.distribute_dofs (fe); + mg_dof_handler.distribute_mg_dofs (fe); + + DoFTools::extract_locally_relevant_dofs (mg_dof_handler, + locally_relevant_set); + + solution.reinit(mg_dof_handler.locally_owned_dofs(), MPI_COMM_WORLD); + system_rhs.reinit(mg_dof_handler.locally_owned_dofs(), MPI_COMM_WORLD); + + constraints.reinit (locally_relevant_set); + hanging_node_constraints.reinit (locally_relevant_set); + DoFTools::make_hanging_node_constraints (mg_dof_handler, hanging_node_constraints); + DoFTools::make_hanging_node_constraints (mg_dof_handler, constraints); + + typename FunctionMap::type dirichlet_boundary; + ZeroFunction homogeneous_dirichlet_bc; + dirichlet_boundary[0] = &homogeneous_dirichlet_bc; + VectorTools::interpolate_boundary_values (mg_dof_handler, + dirichlet_boundary, + constraints); + constraints.close (); + hanging_node_constraints.close (); + + DynamicSparsityPattern dsp(mg_dof_handler.n_dofs(), mg_dof_handler.n_dofs()); + DoFTools::make_sparsity_pattern (mg_dof_handler, dsp, constraints); + system_matrix.reinit (mg_dof_handler.locally_owned_dofs(), dsp, MPI_COMM_WORLD, true); + + + mg_constrained_dofs.clear(); + mg_constrained_dofs.initialize(mg_dof_handler, dirichlet_boundary); + + + const unsigned int n_levels = triangulation.n_global_levels(); + + mg_interface_matrices.resize(0, n_levels-1); + mg_interface_matrices.clear_elements (); + mg_matrices.resize(0, n_levels-1); + mg_matrices.clear_elements (); + + for (unsigned int level=0; level + void LaplaceProblem::assemble_system () + { + const QGauss quadrature_formula(degree+1); + + FEValues fe_values (fe, quadrature_formula, + update_values | update_gradients | + update_quadrature_points | update_JxW_values); + + const unsigned int dofs_per_cell = fe.dofs_per_cell; + const unsigned int n_q_points = quadrature_formula.size(); + + FullMatrix cell_matrix (dofs_per_cell, dofs_per_cell); + Vector cell_rhs (dofs_per_cell); + + std::vector local_dof_indices (dofs_per_cell); + + const Coefficient coefficient; + std::vector coefficient_values (n_q_points); + + typename DoFHandler::active_cell_iterator + cell = mg_dof_handler.begin_active(), + endc = mg_dof_handler.end(); + for (; cell!=endc; ++cell) + if (cell->is_locally_owned()) + { + cell_matrix = 0; + cell_rhs = 0; + + fe_values.reinit (cell); + + coefficient.value_list (fe_values.get_quadrature_points(), + coefficient_values); + + for (unsigned int q_point=0; q_pointget_dof_indices (local_dof_indices); + constraints.distribute_local_to_global (cell_matrix, cell_rhs, + local_dof_indices, + system_matrix, system_rhs); + } + + system_matrix.compress(VectorOperation::add); + system_rhs.compress(VectorOperation::add); + } + + + + template + void LaplaceProblem::assemble_multigrid () + { + QGauss quadrature_formula(1+degree); + + FEValues fe_values (fe, quadrature_formula, + update_values | update_gradients | + update_quadrature_points | update_JxW_values); + + const unsigned int dofs_per_cell = fe.dofs_per_cell; + const unsigned int n_q_points = quadrature_formula.size(); + + FullMatrix cell_matrix (dofs_per_cell, dofs_per_cell); + + std::vector local_dof_indices (dofs_per_cell); + + const Coefficient coefficient; + std::vector coefficient_values (n_q_points); + + + + std::vector boundary_constraints (triangulation.n_global_levels()); + ConstraintMatrix empty_constraints; + for (unsigned int level=0; level::cell_iterator cell = mg_dof_handler.begin(), + endc = mg_dof_handler.end(); + + for (; cell!=endc; ++cell) + if (cell->level_subdomain_id()==triangulation.locally_owned_subdomain()) + { + cell_matrix = 0; + fe_values.reinit (cell); + + coefficient.value_list (fe_values.get_quadrature_points(), + coefficient_values); + + for (unsigned int q_point=0; q_pointget_mg_dof_indices (local_dof_indices); + + boundary_constraints[cell->level()] + .distribute_local_to_global (cell_matrix, + local_dof_indices, + mg_matrices[cell->level()]); + + + const IndexSet &interface_dofs_on_level + = mg_constrained_dofs.get_refinement_edge_indices(cell->level()); + const unsigned int lvl = cell->level(); + + for (unsigned int i=0; ilevel()]); + } + + for (unsigned int i=0; i + void LaplaceProblem::solve () + { + MGTransferPrebuilt mg_transfer(hanging_node_constraints, mg_constrained_dofs); + mg_transfer.build_matrices(mg_dof_handler); + + // pre and post smoothers: + typedef LA::MPI::PreconditionJacobi Smoother; + MGSmootherPrecondition mg_smoother; + mg_smoother.initialize(mg_matrices, Smoother::AdditionalData(0.5)); + mg_smoother.set_steps(2); + + // coarse grid solver: + MGSmootherPrecondition mg_coase_grid_smoother; + mg_coase_grid_smoother.initialize(mg_matrices, Smoother::AdditionalData(0.5)); + mg_coase_grid_smoother.set_steps(2); + mg_coase_grid_smoother.set_symmetric(true); + MGCoarseGridApplySmoother coarse_grid_solver(mg_coase_grid_smoother); + + + mg::Matrix mg_matrix(mg_matrices); + mg::Matrix mg_interface_up(mg_interface_matrices); + mg::Matrix mg_interface_down(mg_interface_matrices); + + Multigrid mg(mg_dof_handler, + mg_matrix, + coarse_grid_solver, + mg_transfer, + mg_smoother, + mg_smoother); + mg.set_edge_matrices(mg_interface_down, mg_interface_up); + + PreconditionMG > + preconditioner(mg_dof_handler, mg, mg_transfer); + + + SolverControl solver_control (500, 1e-8*system_rhs.l2_norm(), false); + SolverCG solver (solver_control); + + solution = 0; + solver.solve (system_matrix, solution, system_rhs, + preconditioner); + constraints.distribute (solution); + } + + + + + template + void LaplaceProblem::refine_grid () + { + Vector estimated_error_per_cell (triangulation.n_active_cells()); + + LA::MPI::Vector temp_solution; + temp_solution.reinit(locally_relevant_set, MPI_COMM_WORLD); + temp_solution = solution; + + KellyErrorEstimator::estimate (static_cast&>(mg_dof_handler), + QGauss(degree+1), + typename FunctionMap::type(), + temp_solution, + estimated_error_per_cell); + + const double threshold = 0.6 * Utilities::MPI::max(estimated_error_per_cell.linfty_norm(),MPI_COMM_WORLD); + GridRefinement::refine (triangulation, estimated_error_per_cell, threshold); + + for (typename Triangulation::active_cell_iterator + cell = triangulation.begin_active(); + cell != triangulation.end(); ++cell) + if (cell->subdomain_id() != triangulation.locally_owned_subdomain()) + { + cell->clear_refine_flag (); + cell->clear_coarsen_flag (); + } + + triangulation.execute_coarsening_and_refinement (); + } + + template + void LaplaceProblem::run () + { + for (unsigned int cycle=0; cycle<5; ++cycle) + { + deallog << "Cycle " << cycle << ':' << std::endl; + + if (cycle == 0) + { + GridGenerator::hyper_cube (triangulation); + + triangulation.refine_global (4); + } + else + refine_grid (); + + deallog << " Number of active cells: " + << triangulation.n_global_active_cells() + << std::endl; + + setup_system (); + + deallog << " Number of degrees of freedom: " + << mg_dof_handler.n_dofs() + << " (by level: "; + for (unsigned int level=0; level laplace_problem(1/*degree*/); + laplace_problem.run (); + } + catch (std::exception &exc) + { + std::cerr << std::endl << std::endl + << "----------------------------------------------------" + << std::endl; + std::cerr << "Exception on processing: " << std::endl + << exc.what() << std::endl + << "Aborting!" << std::endl + << "----------------------------------------------------" + << std::endl; + throw; + } + catch (...) + { + std::cerr << std::endl << std::endl + << "----------------------------------------------------" + << std::endl; + std::cerr << "Unknown exception!" << std::endl + << "Aborting!" << std::endl + << "----------------------------------------------------" + << std::endl; + throw; + } + + return 0; +} diff --git a/tests/multigrid/step-16-50-mpi-smoother.with_mpi=true.with_trilinos=true.with_p4est=true.mpirun=3.output b/tests/multigrid/step-16-50-mpi-smoother.with_mpi=true.with_trilinos=true.with_p4est=true.mpirun=3.output new file mode 100644 index 0000000000..3f3684cfb0 --- /dev/null +++ b/tests/multigrid/step-16-50-mpi-smoother.with_mpi=true.with_trilinos=true.with_p4est=true.mpirun=3.output @@ -0,0 +1,26 @@ + +DEAL::Cycle 0: +DEAL:: Number of active cells: 256 +DEAL:: Number of degrees of freedom: 289 (by level: 4, 9, 25, 81, 289) +DEAL:cg::Starting value 0.585938 +DEAL:cg::Convergence step 7 value 4.58200e-09 +DEAL::Cycle 1: +DEAL:: Number of active cells: 418 +DEAL:: Number of degrees of freedom: 495 (by level: 4, 9, 25, 81, 289, 305) +DEAL:cg::Starting value 0.533937 +DEAL:cg::Convergence step 10 value 7.40543e-10 +DEAL::Cycle 2: +DEAL:: Number of active cells: 865 +DEAL:: Number of degrees of freedom: 952 (by level: 4, 9, 25, 81, 289, 769, 153) +DEAL:cg::Starting value 0.378780 +DEAL:cg::Convergence step 11 value 1.39894e-09 +DEAL::Cycle 3: +DEAL:: Number of active cells: 1219 +DEAL:: Number of degrees of freedom: 1354 (by level: 4, 9, 25, 81, 289, 953, 277, 261) +DEAL:cg::Starting value 0.343729 +DEAL:cg::Convergence step 13 value 6.16552e-10 +DEAL::Cycle 4: +DEAL:: Number of active cells: 1297 +DEAL:: Number of degrees of freedom: 1446 (by level: 4, 9, 25, 81, 289, 961, 313, 349) +DEAL:cg::Starting value 0.339440 +DEAL:cg::Convergence step 13 value 7.00850e-10