fe_q_base.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2013 - 2025 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_fe_q_base_h
#define dealii_fe_q_base_h
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/mutex.h>
 
#include <deal.II/fe/fe_poly.h>
 
DEAL_II_NAMESPACE_OPEN
 
 
template <int dim, int spacedim = dim>
class FE_Q_Base : public FE_Poly<dim, spacedim>
{
public:
  FE_Q_Base(const ScalarPolynomialsBase<dim> &poly_space,
            const FiniteElementData<dim>     &fe_data,
            const std::vector<bool>          &restriction_is_additive_flags);
 
  virtual void
  get_interpolation_matrix(const FiniteElement<dim, spacedim> &source,
                           FullMatrix<double> &matrix) const override;
 
 
  virtual void
  get_face_interpolation_matrix(const FiniteElement<dim, spacedim> &source,
                                FullMatrix<double>                 &matrix,
                                const unsigned int face_no = 0) const override;
 
  virtual void
  get_subface_interpolation_matrix(
    const FiniteElement<dim, spacedim> &source,
    const unsigned int                  subface,
    FullMatrix<double>                 &matrix,
    const unsigned int                  face_no = 0) const override;
 
  virtual bool
  has_support_on_face(const unsigned int shape_index,
                      const unsigned int face_index) const override;
 
  virtual const FullMatrix<double> &
  get_restriction_matrix(
    const unsigned int         child,
    const RefinementCase<dim> &refinement_case =
      RefinementCase<dim>::isotropic_refinement) const override;
 
  virtual const FullMatrix<double> &
  get_prolongation_matrix(
    const unsigned int         child,
    const RefinementCase<dim> &refinement_case =
      RefinementCase<dim>::isotropic_refinement) const override;
 
  virtual unsigned int
  face_to_cell_index(const unsigned int                 face_dof_index,
                     const unsigned int                 face,
                     const types::geometric_orientation combined_orientation =
                       numbers::default_geometric_orientation) const override;
 
  virtual std::pair<Table<2, bool>, std::vector<unsigned int>>
  get_constant_modes() const override;
 
  virtual bool
  hp_constraints_are_implemented() const override;
 
  virtual std::vector<std::pair<unsigned int, unsigned int>>
  hp_vertex_dof_identities(
    const FiniteElement<dim, spacedim> &fe_other) const override;
 
  virtual std::vector<std::pair<unsigned int, unsigned int>>
  hp_line_dof_identities(
    const FiniteElement<dim, spacedim> &fe_other) const override;
 
  virtual std::vector<std::pair<unsigned int, unsigned int>>
  hp_quad_dof_identities(const FiniteElement<dim, spacedim> &fe_other,
                         const unsigned int face_no = 0) const override;
 
  DeclExceptionMsg(ExcFEQCannotHaveDegree0,
                   "FE_Q can only be used for polynomial degrees "
                   "greater than zero. If you want an element of polynomial "
                   "degree zero, then it cannot be continuous and you "
                   "will want to use FE_DGQ<dim>(0).");
 
protected:
  static std::vector<unsigned int>
  get_dpo_vector(const unsigned int degree);
 
  void
  initialize(const std::vector<Point<1>> &support_points_1d);
 
  void
  initialize_constraints(const std::vector<Point<1>> &points);
 
  void
  initialize_unit_support_points(const std::vector<Point<1>> &points);
 
  void
  initialize_unit_face_support_points(const std::vector<Point<1>> &points);
 
  void
  initialize_dof_index_permutations();
 
  struct Implementation;
 
  // Declare implementation friend.
  friend struct FE_Q_Base<dim, spacedim>::Implementation;
 
private:
  mutable Threads::Mutex restriction_matrix_mutex;
  mutable Threads::Mutex prolongation_matrix_mutex;
 
  const unsigned int q_degree;
};
 
 
DEAL_II_NAMESPACE_CLOSE
 
#endif