condensed_eigen_system.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_CONDENSED_EIGEN_SYSTEM_H
#define LIBMESH_CONDENSED_EIGEN_SYSTEM_H

#include "libmesh/libmesh_config.h"

// Currently, the EigenSystem should only be available
// if SLEPc support is enabled.
#if defined(LIBMESH_HAVE_SLEPC)

// Local Includes
#include "libmesh/eigen_system.h"
#include "libmesh/sparse_matrix.h"

namespace libMesh
{

class CondensedEigenSystem : public EigenSystem
{
public:

  CondensedEigenSystem (EquationSystems & es,
                        const std::string & name_in,
                        const unsigned int number_in);

  CondensedEigenSystem (const CondensedEigenSystem &) = delete;
  CondensedEigenSystem & operator= (const CondensedEigenSystem &) = delete;
  CondensedEigenSystem (CondensedEigenSystem &&) = default;
  CondensedEigenSystem & operator= (CondensedEigenSystem &&) = delete;
  virtual ~CondensedEigenSystem ();

  typedef CondensedEigenSystem sys_type;

  typedef EigenSystem Parent;

  sys_type & system () { return *this; }

  void initialize_condensed_dofs(const std::set<dof_id_type> &
                                 global_condensed_dofs_set =
                                 std::set<dof_id_type>());

  dof_id_type n_global_non_condensed_dofs() const;

  virtual void solve() override;

  virtual void clear () override;

  virtual std::pair<Real, Real> get_eigenpair(dof_id_type i) override;

  bool has_condensed_matrix_A() const { return _condensed_matrix_A.get(); }
  bool has_condensed_matrix_B() const { return _condensed_matrix_B.get(); }
  bool has_condensed_precond_matrix() const { return _condensed_precond_matrix.get(); }

  SparseMatrix<Number> & get_condensed_matrix_A();

  SparseMatrix<Number> & get_condensed_matrix_B();

  SparseMatrix<Number> & get_condensed_precond_matrix();

  void copy_sub_to_super(const NumericVector<Number> & sub, NumericVector<Number> & super);

  void copy_super_to_sub(NumericVector<Number> & super, NumericVector<Number> & sub);

  void copy_super_to_sub(const SparseMatrix<Number> & super, SparseMatrix<Number> & sub);

  void dont_create_submatrices_in_solve() { _create_submatrices_in_solve = false; }

  std::vector<dof_id_type> local_non_condensed_dofs_vector;

  void initialize_condensed_matrices();

  bool have_condensed_dofs() const
  { libmesh_assert(_condensed_dofs_initialized); return _have_condensed_dofs; }

  virtual void reinit() override;

protected:
  virtual void add_matrices () override;

private:
  virtual bool condense_constrained_dofs() const override final { return true; }

  bool _condensed_dofs_initialized;

  bool _have_condensed_dofs;

  bool _create_submatrices_in_solve;

  std::unique_ptr<SparseMatrix<Number>> _condensed_matrix_A;

  std::unique_ptr<SparseMatrix<Number>> _condensed_matrix_B;

  std::unique_ptr<SparseMatrix<Number>> _condensed_precond_matrix;
};


} // namespace libMesh


#endif // LIBMESH_HAVE_SLEPC

#endif // LIBMESH_CONDENSED_EIGEN_SYSTEM_H