eigen_solver.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_EIGEN_SOLVER_H
#define LIBMESH_EIGEN_SOLVER_H


#include "libmesh/libmesh_config.h"
#ifdef LIBMESH_HAVE_SLEPC

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

// C++ includes
#include <memory>

namespace libMesh
{

// forward declarations
template <typename T> class SparseMatrix;
template <typename T> class ShellMatrix;
template <typename T> class NumericVector;
class SolverConfiguration;
enum EigenSolverType : int;
enum EigenProblemType : int;
enum PositionOfSpectrum : int;

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

  EigenSolver (const Parallel::Communicator & comm_in);

  virtual ~EigenSolver ();

  static std::unique_ptr<EigenSolver<T>> build(const Parallel::Communicator & comm_in,
                                               const SolverPackage solver_package = SLEPC_SOLVERS);

  bool initialized () const { return _is_initialized; }

  bool get_close_matrix_before_solve() const
  {
    libmesh_experimental();
    return _close_matrix_before_solve;
  }

  void set_close_matrix_before_solve(bool val)
  {
    libmesh_experimental();
    _close_matrix_before_solve = val;
  }

  virtual void clear () {}

  virtual void init () = 0;

  EigenSolverType eigen_solver_type () const { return _eigen_solver_type; }

  EigenProblemType eigen_problem_type () const { return _eigen_problem_type;}

  PositionOfSpectrum position_of_spectrum () const
  { return _position_of_spectrum;}

  void set_eigensolver_type (const EigenSolverType est)
  { _eigen_solver_type = est; }

  void set_eigenproblem_type ( EigenProblemType ept)
  {_eigen_problem_type = ept;}

  void set_position_of_spectrum (PositionOfSpectrum pos)
  {_position_of_spectrum= pos;}

  void set_position_of_spectrum (Real pos);
  void set_position_of_spectrum (Real pos, PositionOfSpectrum target);

  virtual std::pair<unsigned int, unsigned int> solve_standard (SparseMatrix<T> & matrix_A,
                                                                int nev,
                                                                int ncv,
                                                                const double tol,
                                                                const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_standard (ShellMatrix<T> & matrix_A,
                                                                int nev,
                                                                int ncv,
                                                                const double tol,
                                                                const unsigned int m_its) = 0;

   virtual std::pair<unsigned int, unsigned int> solve_standard (ShellMatrix<T> & matrix_A,
                                                                 SparseMatrix<T> & precond,
                                                                 int nev,
                                                                 int ncv,
                                                                 const double tol,
                                                                 const unsigned int m_its) = 0;

   virtual std::pair<unsigned int, unsigned int> solve_standard (ShellMatrix<T> & matrix_A,
                                                                 ShellMatrix<T> & precond,
                                                                 int nev,
                                                                 int ncv,
                                                                 const double tol,
                                                                 const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_generalized (SparseMatrix<T> & matrix_A,
                                                                   SparseMatrix<T> & matrix_B,
                                                                   int nev,
                                                                   int ncv,
                                                                   const double tol,
                                                                   const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_generalized (ShellMatrix<T> & matrix_A,
                                                                   SparseMatrix<T> & matrix_B,
                                                                   int nev,
                                                                   int ncv,
                                                                   const double tol,
                                                                   const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_generalized (SparseMatrix<T> & matrix_A,
                                                                   ShellMatrix<T> & matrix_B,
                                                                   int nev,
                                                                   int ncv,
                                                                   const double tol,
                                                                   const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_generalized (ShellMatrix<T> & matrix_A,
                                                                   ShellMatrix<T> & matrix_B,
                                                                   int nev,
                                                                   int ncv,
                                                                   const double tol,
                                                                   const unsigned int m_its) = 0;

   virtual std::pair<unsigned int, unsigned int> solve_generalized (ShellMatrix<T> & matrix_A,
                                                                    ShellMatrix<T> & matrix_B,
                                                                    SparseMatrix<T> & precond,
                                                                    int nev,
                                                                    int ncv,
                                                                    const double tol,
                                                                    const unsigned int m_its) = 0;

  virtual std::pair<unsigned int, unsigned int> solve_generalized (ShellMatrix<T> & matrix_A,
                                                                   ShellMatrix<T> & matrix_B,
                                                                   ShellMatrix<T> & precond,
                                                                   int nev,
                                                                   int ncv,
                                                                   const double tol,
                                                                   const unsigned int m_its) = 0;


  virtual std::pair<Real, Real> get_eigenpair (dof_id_type i,
                                               NumericVector<T> & solution) = 0;

  virtual std::pair<Real, Real> get_eigenvalue (dof_id_type i) = 0;

  virtual void attach_deflation_space(NumericVector<T> & deflation_vector) = 0;

  virtual void set_initial_space(NumericVector<T> & initial_space_in) = 0;

  void set_solver_configuration(SolverConfiguration & solver_configuration);

protected:

  EigenSolverType _eigen_solver_type;

  EigenProblemType _eigen_problem_type;

  PositionOfSpectrum _position_of_spectrum;

  bool _is_initialized;

  SolverConfiguration * _solver_configuration;

  Real _target_val;

  bool _close_matrix_before_solve;
};

} // namespace libMesh

#endif // LIBMESH_HAVE_SLEPC

#endif // LIBMESH_EIGEN_SOLVER_H