nonlinear_solver.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_NONLINEAR_SOLVER_H
#define LIBMESH_NONLINEAR_SOLVER_H
 
// Local includes
#include "libmesh/libmesh_common.h"
#include "libmesh/reference_counted_object.h"
#include "libmesh/nonlinear_implicit_system.h"
#include "libmesh/libmesh.h"
#include "libmesh/parallel_object.h"
 
// C++ includes
#include <cstddef>
#include <memory>
 
namespace libMesh
{
 
// forward declarations
template <typename T> class SparseMatrix;
template <typename T> class NumericVector;
template <typename T> class Preconditioner;
class SolverConfiguration;
enum SolverPackage : int;
 
template <typename T>
class NonlinearSolver : public ReferenceCountedObject<NonlinearSolver<T>>,
                        public ParallelObject
{
public:
  typedef NonlinearImplicitSystem sys_type;
 
  explicit
  NonlinearSolver (sys_type & s);
 
  virtual ~NonlinearSolver ();
 
  static std::unique_ptr<NonlinearSolver<T>> build(sys_type & s,
                                                   const SolverPackage solver_package = libMesh::default_solver_package());
 
  bool initialized () const { return _is_initialized; }
 
  virtual void clear () {}
 
  virtual void init (const char * name = nullptr) = 0;
 
  virtual std::pair<unsigned int, Real> solve (SparseMatrix<T> &,  // System Jacobian Matrix
                                               NumericVector<T> &, // Solution vector
                                               NumericVector<T> &, // Residual vector
                                               const double,      // Stopping tolerance
                                               const unsigned int) = 0; // N. Iterations
 
  virtual void print_converged_reason() { libmesh_not_implemented(); }
 
  virtual int get_total_linear_iterations() = 0;
 
  virtual unsigned get_current_nonlinear_iteration_number() const = 0;
 
  void (* residual) (const NumericVector<Number> & X,
                     NumericVector<Number> & R,
                     sys_type & S);
 
  NonlinearImplicitSystem::ComputeResidual * residual_object;
 
  NonlinearImplicitSystem::ComputeResidual * fd_residual_object;
 
  NonlinearImplicitSystem::ComputeResidual * mffd_residual_object;
 
  void (* jacobian) (const NumericVector<Number> & X,
                     SparseMatrix<Number> & J,
                     sys_type & S);
 
  NonlinearImplicitSystem::ComputeJacobian * jacobian_object;
 
  void (* matvec) (const NumericVector<Number> & X,
                   NumericVector<Number> * R,
                   SparseMatrix<Number> * J,
                   sys_type & S);
 
  NonlinearImplicitSystem::ComputeResidualandJacobian * residual_and_jacobian_object;
 
  void (* bounds) (NumericVector<Number> & XL,
                   NumericVector<Number> & XU,
                   sys_type & S);
  NonlinearImplicitSystem::ComputeBounds * bounds_object;
 
  void (* nullspace) (std::vector<NumericVector<Number> *> & sp, sys_type & S);
 
  NonlinearImplicitSystem::ComputeVectorSubspace * nullspace_object;
 
  void (* transpose_nullspace) (std::vector<NumericVector<Number> *> & sp, sys_type & S);
 
  NonlinearImplicitSystem::ComputeVectorSubspace * transpose_nullspace_object;
 
  void (* nearnullspace) (std::vector<NumericVector<Number> *> & sp, sys_type & S);
 
  NonlinearImplicitSystem::ComputeVectorSubspace * nearnullspace_object;
 
  void (* user_presolve)(sys_type & S);
 
  void (* postcheck) (const NumericVector<Number> & old_soln,
                      NumericVector<Number> & search_direction,
                      NumericVector<Number> & new_soln,
                      bool & changed_search_direction,
                      bool & changed_new_soln,
                      sys_type & S);
 
  NonlinearImplicitSystem::ComputePostCheck * postcheck_object;
 
  NonlinearImplicitSystem::ComputePreCheck * precheck_object;
 
  const sys_type & system () const { return _system; }
 
  sys_type & system () { return _system; }
 
  void attach_preconditioner(Preconditioner<T> * preconditioner);
 
  unsigned int max_nonlinear_iterations;
 
  unsigned int max_function_evaluations;
 
  double absolute_residual_tolerance;
  double relative_residual_tolerance;
 
  double divergence_tolerance;
 
  double absolute_step_tolerance;
  double relative_step_tolerance;
 
  unsigned int max_linear_iterations;
 
  double initial_linear_tolerance;
 
  double minimum_linear_tolerance;
 
  bool converged;
 
  void set_solver_configuration(SolverConfiguration & solver_configuration);
 
  virtual bool reuse_preconditioner() const;
 
  virtual void set_reuse_preconditioner(bool reuse);
 
  virtual unsigned int reuse_preconditioner_max_linear_its() const;
 
  virtual void set_reuse_preconditioner_max_linear_its(unsigned int i);
 
  virtual void force_new_preconditioner() {};
 
  virtual void set_exact_constraint_enforcement(bool enable)
  {
    _exact_constraint_enforcement = enable;
  }
 
  bool exact_constraint_enforcement()
  {
    return _exact_constraint_enforcement;
  }
 
protected:
  bool _reuse_preconditioner;
 
  bool _exact_constraint_enforcement;
 
  unsigned int _reuse_preconditioner_max_linear_its;
 
  sys_type & _system;
 
  bool _is_initialized;
 
  Preconditioner<T> * _preconditioner;
 
  SolverConfiguration * _solver_configuration;
};
 
 
 
 
/*----------------------- inline functions ----------------------------------*/
template <typename T>
inline
NonlinearSolver<T>::NonlinearSolver (sys_type & s) :
  ParallelObject               (s),
  residual                     (nullptr),
  residual_object              (nullptr),
  fd_residual_object           (nullptr),
  mffd_residual_object         (nullptr),
  jacobian                     (nullptr),
  jacobian_object              (nullptr),
  matvec                       (nullptr),
  residual_and_jacobian_object (nullptr),
  bounds                       (nullptr),
  bounds_object                (nullptr),
  nullspace                    (nullptr),
  nullspace_object             (nullptr),
  transpose_nullspace          (nullptr),
  transpose_nullspace_object   (nullptr),
  nearnullspace                (nullptr),
  nearnullspace_object         (nullptr),
  user_presolve                (nullptr),
  postcheck                    (nullptr),
  postcheck_object             (nullptr),
  precheck_object              (nullptr),
  max_nonlinear_iterations(0),
  max_function_evaluations(0),
  absolute_residual_tolerance(0),
  relative_residual_tolerance(0),
  divergence_tolerance(0),
  absolute_step_tolerance(0),
  relative_step_tolerance(0),
  max_linear_iterations(0),
  initial_linear_tolerance(0),
  minimum_linear_tolerance(0),
  converged(false),
  _reuse_preconditioner(false),
  _exact_constraint_enforcement(true),
  _reuse_preconditioner_max_linear_its(0),
  _system(s),
  _is_initialized (false),
  _preconditioner (nullptr),
  _solver_configuration(nullptr)
{
}
 
 
 
template <typename T>
inline
NonlinearSolver<T>::~NonlinearSolver ()
{
  this->NonlinearSolver::clear ();
}
 
 
} // namespace libMesh
 
 
#endif // LIBMESH_NONLINEAR_SOLVER_H