petsc_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_PETSC_NONLINEAR_SOLVER_H
#define LIBMESH_PETSC_NONLINEAR_SOLVER_H

#include "libmesh/libmesh_config.h"

// Petsc include files.
#ifdef LIBMESH_HAVE_PETSC

// Local includes
#include "libmesh/nonlinear_solver.h"
#include "libmesh/petsc_macro.h"
#include "libmesh/wrapped_petsc.h"
#include "libmesh/petsc_dm_wrapper.h"
#include "libmesh/petsc_mffd_matrix.h"

// PETSc includes
#ifdef I
# define LIBMESH_SAW_I
#endif
#include <petscsnes.h>
#ifndef LIBMESH_SAW_I
# undef I // Avoid complex.h contamination
#endif

namespace libMesh
{
class ResidualContext;

// Allow users access to these functions in case they want to reuse them.  Users shouldn't
// need access to these most of the time as they are used internally by this object.
extern "C"
{
  PetscErrorCode libmesh_petsc_recalculate_monitor(SNES snes, PetscInt it, PetscReal norm, void* mctx);
  PetscErrorCode libmesh_petsc_snes_monitor (SNES, PetscInt its, PetscReal fnorm, void *);
  PetscErrorCode libmesh_petsc_snes_residual (SNES, Vec x, Vec r, void * ctx);
  PetscErrorCode libmesh_petsc_snes_fd_residual (SNES, Vec x, Vec r, void * ctx);
  PetscErrorCode libmesh_petsc_snes_mffd_residual (SNES snes, Vec x, Vec r, void * ctx);
  PetscErrorCode libmesh_petsc_snes_mffd_interface (void * ctx, Vec x, Vec r);
  PetscErrorCode libmesh_petsc_snes_jacobian (SNES, Vec x, Mat jac, Mat pc, void * ctx);
  PetscErrorCode libmesh_petsc_snes_precheck(SNESLineSearch, Vec X, Vec Y, PetscBool * changed, void * context);
  PetscErrorCode libmesh_petsc_snes_postcheck(SNESLineSearch, Vec x, Vec y, Vec w, PetscBool * changed_y, PetscBool * changed_w, void * context);
  PetscErrorCode libmesh_petsc_linesearch_shellfunc(SNESLineSearch linesearch, void * ctx);
}

template <typename T>
class PetscNonlinearSolver : public NonlinearSolver<T>
{
public:
  typedef NonlinearImplicitSystem sys_type;

  explicit
  PetscNonlinearSolver (sys_type & system);

  ~PetscNonlinearSolver ();

  virtual void clear () override;

  virtual void init (const char * name = nullptr) override;

  SNES snes(const char * name = nullptr);

  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) override; // N. Iterations

  virtual void print_converged_reason() override;

  SNESConvergedReason get_converged_reason();

  virtual int get_total_linear_iterations() override;

  virtual unsigned get_current_nonlinear_iteration_number() const override
  { return _current_nonlinear_iteration_number; }

  void set_residual_zero_out(bool state) { _zero_out_residual = state; }

  void set_jacobian_zero_out(bool state) { _zero_out_jacobian = state; }

  void use_default_monitor(bool state) { _default_monitor = state; }

  void set_snesmf_reuse_base(bool state) { _snesmf_reuse_base = state; }

  bool snes_mf_reuse_base() const { return _snesmf_reuse_base; }

  void set_computing_base_vector(bool computing_base_vector) { _computing_base_vector = computing_base_vector; }

  bool computing_base_vector() const { return _computing_base_vector; }

  class ComputeLineSearchObject
  {
  public:
    virtual ~ComputeLineSearchObject () = default;

    virtual void linesearch (SNESLineSearch linesearch) = 0;
  };

  std::unique_ptr<ComputeLineSearchObject> linesearch_object;

  void setup_default_monitor();

  virtual bool reuse_preconditioner() const override;

  virtual unsigned int reuse_preconditioner_max_linear_its() const override;

  virtual void force_new_preconditioner() override;

protected:

  WrappedPetsc<SNES> _snes;

  SNESConvergedReason _reason;

  PetscInt _n_linear_iterations;

  unsigned _current_nonlinear_iteration_number;

  bool _zero_out_residual;

  bool _zero_out_jacobian;

  bool _default_monitor;

  bool _snesmf_reuse_base;

  void build_mat_null_space(NonlinearImplicitSystem::ComputeVectorSubspace * computeSubspaceObject,
                            void (*)(std::vector<NumericVector<Number> *> &, sys_type &),
                            MatNullSpace *);

  bool _computing_base_vector;

  bool _setup_reuse;

#if defined(LIBMESH_ENABLE_AMR) && defined(LIBMESH_HAVE_METAPHYSICL)

  PetscDMWrapper _dm_wrapper;
#endif

  PetscMFFDMatrix<Number> _mffd_jac;

private:
  friend ResidualContext libmesh_petsc_snes_residual_helper (SNES snes, Vec x, void * ctx);
  friend PetscErrorCode libmesh_petsc_snes_residual (SNES snes, Vec x, Vec r, void * ctx);
  friend PetscErrorCode libmesh_petsc_snes_fd_residual (SNES snes, Vec x, Vec r, void * ctx);
  friend PetscErrorCode libmesh_petsc_snes_mffd_residual (SNES snes, Vec x, Vec r, void * ctx);
  friend PetscErrorCode libmesh_petsc_snes_jacobian (SNES snes, Vec x, Mat jac, Mat pc, void * ctx);
  friend PetscErrorCode libmesh_petsc_snes_precheck (SNESLineSearch,
                                                     Vec X,
                                                     Vec Y,
                                                     PetscBool * changed,
                                                     void * context);
};

} // namespace libMesh


#endif // #ifdef LIBMESH_HAVE_PETSC
#endif // LIBMESH_PETSC_NONLINEAR_SOLVER_H