unsteady_solver.C

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2019 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
 
// This library is free software; you can 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.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 
#include "libmesh/diff_solver.h"
#include "libmesh/diff_system.h"
#include "libmesh/dof_map.h"
#include "libmesh/numeric_vector.h"
#include "libmesh/unsteady_solver.h"
 
namespace libMesh
{
 
 
 
UnsteadySolver::UnsteadySolver (sys_type & s)
  : TimeSolver(s),
    old_local_nonlinear_solution (NumericVector<Number>::build(s.comm())),
    first_solve                  (true),
    first_adjoint_step (true)
{
}
 
 
 
UnsteadySolver::~UnsteadySolver ()
{
}
 
 
 
void UnsteadySolver::init ()
{
  TimeSolver::init();
 
  _system.add_vector("_old_nonlinear_solution");
}
 
 
 
void UnsteadySolver::init_data()
{
  TimeSolver::init_data();
 
#ifdef LIBMESH_ENABLE_GHOSTED
  old_local_nonlinear_solution->init (_system.n_dofs(), _system.n_local_dofs(),
                                      _system.get_dof_map().get_send_list(), false,
                                      GHOSTED);
#else
  old_local_nonlinear_solution->init (_system.n_dofs(), false, SERIAL);
#endif
}
 
 
 
void UnsteadySolver::reinit ()
{
  TimeSolver::reinit();
 
#ifdef LIBMESH_ENABLE_GHOSTED
  old_local_nonlinear_solution->init (_system.n_dofs(), _system.n_local_dofs(),
                                      _system.get_dof_map().get_send_list(), false,
                                      GHOSTED);
#else
  old_local_nonlinear_solution->init (_system.n_dofs(), false, SERIAL);
#endif
 
  // localize the old solution
  NumericVector<Number> & old_nonlinear_soln =
    _system.get_vector("_old_nonlinear_solution");
 
  old_nonlinear_soln.localize
    (*old_local_nonlinear_solution,
     _system.get_dof_map().get_send_list());
}
 
 
 
void UnsteadySolver::solve ()
{
  if (first_solve)
    {
      advance_timestep();
      first_solve = false;
    }
 
  unsigned int solve_result = _diff_solver->solve();
 
  // If we requested the UnsteadySolver to attempt reducing dt after a
  // failed DiffSolver solve, check the results of the solve now.
  if (reduce_deltat_on_diffsolver_failure)
    {
      bool backtracking_failed =
        solve_result & DiffSolver::DIVERGED_BACKTRACKING_FAILURE;
 
      bool max_iterations =
        solve_result & DiffSolver::DIVERGED_MAX_NONLINEAR_ITERATIONS;
 
      if (backtracking_failed || max_iterations)
        {
          // Cut timestep in half
          for (unsigned int nr=0; nr<reduce_deltat_on_diffsolver_failure; ++nr)
            {
              _system.deltat *= 0.5;
              libMesh::out << "Newton backtracking failed.  Trying with smaller timestep, dt="
                           << _system.deltat << std::endl;
 
              solve_result = _diff_solver->solve();
 
              // Check solve results with reduced timestep
              bool backtracking_still_failed =
                solve_result & DiffSolver::DIVERGED_BACKTRACKING_FAILURE;
 
              bool backtracking_max_iterations =
                solve_result & DiffSolver::DIVERGED_MAX_NONLINEAR_ITERATIONS;
 
              if (!backtracking_still_failed && !backtracking_max_iterations)
                {
                  if (!quiet)
                    libMesh::out << "Reduced dt solve succeeded." << std::endl;
                  return;
                }
            }
 
          // If we made it here, we still couldn't converge the solve after
          // reducing deltat
          libMesh::out << "DiffSolver::solve() did not succeed after "
                       << reduce_deltat_on_diffsolver_failure
                       << " attempts." << std::endl;
          libmesh_convergence_failure();
 
        } // end if (backtracking_failed || max_iterations)
    } // end if (reduce_deltat_on_diffsolver_failure)
}
 
 
 
void UnsteadySolver::advance_timestep ()
{
  if (!first_solve)
    {
      // Store the solution, does nothing by default
      // User has to attach appropriate solution_history object for this to
      // actually store anything anywhere
      solution_history->store();
 
      _system.time += _system.deltat;
    }
 
  NumericVector<Number> & old_nonlinear_soln =
    _system.get_vector("_old_nonlinear_solution");
  NumericVector<Number> & nonlinear_solution =
    *(_system.solution);
 
  old_nonlinear_soln = nonlinear_solution;
 
  old_nonlinear_soln.localize
    (*old_local_nonlinear_solution,
     _system.get_dof_map().get_send_list());
}
 
 
 
void UnsteadySolver::adjoint_advance_timestep ()
{
  // On the first call of this function, we dont save the adjoint solution or
  // decrement the time, we just call the retrieve function below
  if (!first_adjoint_step)
    {
      // Call the store function to store the last adjoint before decrementing the time
      solution_history->store();
      // Decrement the system time
      _system.time -= _system.deltat;
    }
  else
    {
      first_adjoint_step = false;
    }
 
  // Retrieve the primal solution vectors at this time using the
  // solution_history object
  solution_history->retrieve();
 
  // Dont forget to localize the old_nonlinear_solution !
  _system.get_vector("_old_nonlinear_solution").localize
    (*old_local_nonlinear_solution,
     _system.get_dof_map().get_send_list());
}
 
void UnsteadySolver::retrieve_timestep()
{
  // Retrieve all the stored vectors at the current time
  solution_history->retrieve();
 
  // Dont forget to localize the old_nonlinear_solution !
  _system.get_vector("_old_nonlinear_solution").localize
    (*old_local_nonlinear_solution,
     _system.get_dof_map().get_send_list());
}
 
 
Number UnsteadySolver::old_nonlinear_solution(const dof_id_type global_dof_number)
  const
{
  libmesh_assert_less (global_dof_number, _system.get_dof_map().n_dofs());
  libmesh_assert_less (global_dof_number, old_local_nonlinear_solution->size());
 
  return (*old_local_nonlinear_solution)(global_dof_number);
}
 
 
 
Real UnsteadySolver::du(const SystemNorm & norm) const
{
 
  std::unique_ptr<NumericVector<Number>> solution_copy =
    _system.solution->clone();
 
  solution_copy->add(-1., _system.get_vector("_old_nonlinear_solution"));
 
  solution_copy->close();
 
  return _system.calculate_norm(*solution_copy, norm);
}
 
} // namespace libMesh