continuation_system.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 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
 
 
 
#ifndef LIBMESH_CONTINUATION_SYSTEM_H
#define LIBMESH_CONTINUATION_SYSTEM_H
 
// Local Includes
#include "libmesh/fem_system.h"
 
namespace libMesh
{
 
// Forward Declarations
template <typename T> class LinearSolver;
class NewtonSolver;
 
class ContinuationSystem : public FEMSystem
{
public:
  ContinuationSystem (EquationSystems & es,
                      const std::string & name,
                      const unsigned int number);
 
  ContinuationSystem (const ContinuationSystem &) = delete;
  ContinuationSystem & operator= (const ContinuationSystem &) = delete;
  ContinuationSystem (ContinuationSystem &&) = delete;
  ContinuationSystem & operator= (ContinuationSystem &&) = delete;
  virtual ~ContinuationSystem ();
 
  typedef ContinuationSystem sys_type;
 
  typedef FEMSystem Parent;
 
  virtual void clear () override;
 
  virtual void solve () override;
 
  void continuation_solve();
 
  void advance_arcstep();
 
  Real * continuation_parameter;
 
  bool quiet;
 
  void set_max_arclength_stepsize(Real maxds) { ds=maxds; ds_current=maxds; }
 
  double continuation_parameter_tolerance;
 
  double solution_tolerance;
 
  double initial_newton_tolerance;
 
  void save_current_solution();
 
  Real old_continuation_parameter;
 
  Real min_continuation_parameter;
 
  Real max_continuation_parameter;
 
  Real Theta;
 
  Real Theta_LOCA;
 
  //Real tau;
 
  unsigned int n_backtrack_steps;
 
  unsigned int n_arclength_reductions;
 
  Real ds_min;
 
  enum Predictor {
    Euler,
 
    AB2,
 
    Invalid_Predictor
  };
 
  Predictor predictor;
 
  Real newton_stepgrowth_aggressiveness;
 
  bool newton_progress_check;
 
protected:
  virtual void init_data () override;
 
  enum RHS_Mode {Residual,
                 G_Lambda};
 
  RHS_Mode rhs_mode;
 
 
 
private:
  void initialize_tangent();
 
  void solve_tangent();
 
  void update_solution();
 
  void set_Theta();
 
  void set_Theta_LOCA();
 
  void apply_predictor();
 
  NumericVector<Number> * du_ds;
 
  NumericVector<Number> * previous_du_ds;
 
  NumericVector<Number> * previous_u;
 
  NumericVector<Number> * y;
 
  NumericVector<Number> * y_old;
 
  NumericVector<Number> * z;
 
  NumericVector<Number> * delta_u;
 
  bool tangent_initialized;
 
  NewtonSolver * newton_solver;
 
  Real dlambda_ds;
 
  Real ds;
 
  Real ds_current;
 
  Real previous_dlambda_ds;
 
  Real previous_ds;
 
  unsigned int newton_step;
};
 
} // namespace libMesh
 
#endif // LIBMESH_CONTINUATION_SYSTEM_H