preconditioner.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_PRECONDITIONER_H
#define LIBMESH_PRECONDITIONER_H


// Local includes
#include "libmesh/libmesh_common.h"
#include "libmesh/reference_counted_object.h"
#include "libmesh/libmesh.h"
#include "libmesh/parallel_object.h"

// C++ includes
#include <cstddef>

namespace libMesh
{

// forward declarations
template <typename T> class SparseMatrix;
template <typename T> class NumericVector;
template <typename T> class ShellMatrix;
enum SolverPackage : int;
enum PreconditionerType : int;

template <typename T>
class Preconditioner : public ReferenceCountedObject<Preconditioner<T>>,
                       public ParallelObject
{
public:

  Preconditioner (const libMesh::Parallel::Communicator & comm);

  virtual ~Preconditioner ();

  static std::unique_ptr<Preconditioner<T>>
  build_preconditioner(const libMesh::Parallel::Communicator & comm,
                       const SolverPackage solver_package = libMesh::default_solver_package());

  virtual bool initialized () const { return _is_initialized; }

  virtual void apply(const NumericVector<T> & x, NumericVector<T> & y) = 0;

  virtual void clear () {}

  virtual void init () {}

  virtual void setup () {}

  virtual void zero() {}

  void set_matrix(SparseMatrix<Number> & mat);

  PreconditionerType type () const { return _preconditioner_type; }

  void set_type (const PreconditionerType pct);

protected:

  SparseMatrix<T> * _matrix;

  PreconditionerType _preconditioner_type;

  bool _is_initialized;
};




/*----------------------- inline functions ----------------------------------*/
template <typename T>
inline
Preconditioner<T>::~Preconditioner ()
{
  this->clear ();
}

template <typename T>
void
Preconditioner<T>::set_matrix(SparseMatrix<Number> & mat)
{
  //If the matrix is changing then we (probably) need to reinitialize.
  _is_initialized = false;
  _matrix = &mat;
}

template <typename T>
void
Preconditioner<T>::set_type (const PreconditionerType pct)
{
  //If the preconditioner type changes we (probably) need to reinitialize.
  _is_initialized = false;
  _preconditioner_type = pct;
}

} // namespace libMesh


#endif // LIBMESH_PRECONDITIONER_H