fem_system.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2025 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_FEM_SYSTEM_H
#define LIBMESH_FEM_SYSTEM_H

// Local Includes
#include "libmesh/diff_system.h"
#include "libmesh/fem_physics.h"

// C++ includes
#include <cstddef>

namespace libMesh
{

// Forward Declarations
class DiffContext;
class FEMContext;


class FEMSystem : public DifferentiableSystem,
                  public FEMPhysics
{
public:

  FEMSystem (EquationSystems & es,
             const std::string & name,
             const unsigned int number);

  FEMSystem (const FEMSystem &) = delete;
  FEMSystem & operator= (const FEMSystem &) = delete;
  FEMSystem (FEMSystem &&) = delete;
  FEMSystem & operator= (FEMSystem &&) = delete;
  virtual ~FEMSystem ();

  typedef FEMSystem sys_type;

  typedef DifferentiableSystem Parent;

  virtual void assembly (bool get_residual,
                         bool get_jacobian,
                         bool apply_heterogeneous_constraints = false,
                         bool apply_no_constraints = false) override;

  virtual void solve () override;

  void mesh_position_get();

  void mesh_position_set();

  virtual std::unique_ptr<DiffContext> build_context() override;

  /*
   * Prepares the result of a build_context() call for use.
   *
   * Most FEMSystem-based problems will need to reimplement this in order to
   * call FE::get_*() as their particular physics requires.
   */
  virtual void init_context(DiffContext &) override;

  virtual void postprocess () override;

  virtual void assemble_qoi (const QoISet & indices = QoISet()) override;

  virtual void assemble_qoi_derivative (const QoISet & qoi_indices = QoISet(),
                                        bool include_liftfunc = true,
                                        bool apply_constraints = true) override;

  bool fe_reinit_during_postprocess;

  Real numerical_jacobian_h;

  Real numerical_jacobian_h_for_var(unsigned int var_num) const;

  void set_numerical_jacobian_h_for_var(unsigned int var_num, Real new_h);

  Real verify_analytic_jacobians;

  typedef bool (TimeSolver::*TimeSolverResPtr)(bool, DiffContext &);

  void numerical_jacobian (TimeSolverResPtr res,
                           FEMContext & context) const;

  void numerical_elem_jacobian (FEMContext & context) const;

  void numerical_side_jacobian (FEMContext & context) const;

  void numerical_nonlocal_jacobian (FEMContext & context) const;

protected:
  virtual void init_data () override;

private:
  std::vector<Real> _numerical_jacobian_h_for_var;
};

// --------------------------------------------------------------
// FEMSystem inline methods
inline
Real
FEMSystem::numerical_jacobian_h_for_var(unsigned int var_num) const
{
  if ((var_num >= _numerical_jacobian_h_for_var.size()) ||
      _numerical_jacobian_h_for_var[var_num] == Real(0))
    return numerical_jacobian_h;

  return _numerical_jacobian_h_for_var[var_num];
}

inline
void FEMSystem::set_numerical_jacobian_h_for_var(unsigned int var_num,
                                                 Real new_h)
{
  if (_numerical_jacobian_h_for_var.size() <= var_num)
    _numerical_jacobian_h_for_var.resize(var_num+1,Real(0));

  libmesh_assert_greater(new_h, Real(0));

  _numerical_jacobian_h_for_var[var_num] = new_h;
}

} // namespace libMesh


#endif // LIBMESH_FEM_SYSTEM_H