mapping_fe.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2015 - 2026 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_mapping_fe_h
#define dealii_mapping_fe_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/derivative_form.h>
#include <deal.II/base/quadrature_lib.h>
#include <deal.II/base/table.h>
#include <deal.II/base/vectorization.h>
 
#include <deal.II/fe/mapping.h>
 
#include <deal.II/grid/tria_iterator.h>
 
#include <boost/container/small_vector.hpp>
 
#include <array>
#include <cmath>
 
DEAL_II_NAMESPACE_OPEN
 


template <int dim, int spacedim = dim>
class MappingFE : public Mapping<dim, spacedim>
{
public:
  explicit MappingFE(const FiniteElement<dim, spacedim> &fe);

  MappingFE(const MappingFE<dim, spacedim> &mapping);
 
  // for documentation, see the Mapping base class
  virtual std::unique_ptr<Mapping<dim, spacedim>>
  clone() const override;

  unsigned int
  get_degree() const;
 
  // for documentation, see the Mapping base class
  virtual BoundingBox<spacedim>
  get_bounding_box(const typename Triangulation<dim, spacedim>::cell_iterator
                     &cell) const override;
 
 
  virtual bool
  is_compatible_with(const ReferenceCell<dim> &reference_cell) const override;

  virtual bool
  preserves_vertex_locations() const override;

 
  // for documentation, see the Mapping base class
  virtual Point<spacedim>
  transform_unit_to_real_cell(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const Point<dim> &p) const override;
 
  // for documentation, see the Mapping base class
  virtual Point<dim>
  transform_real_to_unit_cell(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const Point<spacedim> &p) const override;


 
  // for documentation, see the Mapping base class
  virtual void
  transform(const ArrayView<const Tensor<1, dim>>                   &input,
            const MappingKind                                        kind,
            const typename Mapping<dim, spacedim>::InternalDataBase &internal,
            const ArrayView<Tensor<1, spacedim>> &output) const override;
 
  // for documentation, see the Mapping base class
  virtual void
  transform(const ArrayView<const DerivativeForm<1, dim, spacedim>> &input,
            const MappingKind                                        kind,
            const typename Mapping<dim, spacedim>::InternalDataBase &internal,
            const ArrayView<Tensor<2, spacedim>> &output) const override;
 
  // for documentation, see the Mapping base class
  virtual void
  transform(const ArrayView<const Tensor<2, dim>>                   &input,
            const MappingKind                                        kind,
            const typename Mapping<dim, spacedim>::InternalDataBase &internal,
            const ArrayView<Tensor<2, spacedim>> &output) const override;
 
  // for documentation, see the Mapping base class
  virtual void
  transform(const ArrayView<const DerivativeForm<2, dim, spacedim>> &input,
            const MappingKind                                        kind,
            const typename Mapping<dim, spacedim>::InternalDataBase &internal,
            const ArrayView<Tensor<3, spacedim>> &output) const override;
 
  // for documentation, see the Mapping base class
  virtual void
  transform(const ArrayView<const Tensor<3, dim>>                   &input,
            const MappingKind                                        kind,
            const typename Mapping<dim, spacedim>::InternalDataBase &internal,
            const ArrayView<Tensor<3, spacedim>> &output) const override;



  class InternalData : public Mapping<dim, spacedim>::InternalDataBase
  {
  public:
    InternalData(const FiniteElement<dim, spacedim> &fe);
 
    // Documentation see Mapping::InternalDataBase.
    virtual void
    reinit(const UpdateFlags      update_flags,
           const Quadrature<dim> &quadrature) override;

    void
    initialize_face(const UpdateFlags      update_flags,
                    const Quadrature<dim> &quadrature,
                    const unsigned int     n_original_q_points);

    void
    compute_shape_function_values(const std::vector<Point<dim>> &unit_points);
 

    const double &
    shape(const unsigned int qpoint, const unsigned int shape_nr) const;

    double &
    shape(const unsigned int qpoint, const unsigned int shape_nr);

    const Tensor<1, dim> &
    derivative(const unsigned int qpoint, const unsigned int shape_nr) const;

    Tensor<1, dim> &
    derivative(const unsigned int qpoint, const unsigned int shape_nr);

    const Tensor<2, dim> &
    second_derivative(const unsigned int qpoint,
                      const unsigned int shape_nr) const;

    Tensor<2, dim> &
    second_derivative(const unsigned int qpoint, const unsigned int shape_nr);

    const Tensor<3, dim> &
    third_derivative(const unsigned int qpoint,
                     const unsigned int shape_nr) const;

    Tensor<3, dim> &
    third_derivative(const unsigned int qpoint, const unsigned int shape_nr);

    const Tensor<4, dim> &
    fourth_derivative(const unsigned int qpoint,
                      const unsigned int shape_nr) const;

    Tensor<4, dim> &
    fourth_derivative(const unsigned int qpoint, const unsigned int shape_nr);

    virtual std::size_t
    memory_consumption() const override;

    std::vector<double> shape_values;

    std::vector<Tensor<1, dim>> shape_derivatives;

    std::vector<Tensor<2, dim>> shape_second_derivatives;

    std::vector<Tensor<3, dim>> shape_third_derivatives;

    std::vector<Tensor<4, dim>> shape_fourth_derivatives;

    std::array<std::vector<Tensor<1, dim>>,
               ReferenceCells::max_n_faces<dim>() * 2>
      unit_tangentials;

    const FiniteElement<dim, spacedim> &fe;

    const unsigned int polynomial_degree;

    const unsigned int n_shape_functions;

    mutable std::vector<DerivativeForm<1, dim, spacedim>> covariant;

    mutable std::vector<DerivativeForm<1, dim, spacedim>> contravariant;

    mutable std::vector<std::vector<Tensor<1, spacedim>>> aux;

    mutable std::vector<Point<spacedim>> mapping_support_points;

    mutable std::vector<double> volume_elements;

    mutable std::vector<double> quadrature_weights;
  };
 
 
  // documentation can be found in Mapping::requires_update_flags()
  virtual UpdateFlags
  requires_update_flags(const UpdateFlags update_flags) const override;
 
  // documentation can be found in Mapping::get_data()
  virtual std::unique_ptr<typename Mapping<dim, spacedim>::InternalDataBase>
  get_data(const UpdateFlags, const Quadrature<dim> &quadrature) const override;
 
  using Mapping<dim, spacedim>::get_face_data;
 
  // documentation can be found in Mapping::get_face_data()
  virtual std::unique_ptr<typename Mapping<dim, spacedim>::InternalDataBase>
  get_face_data(const UpdateFlags               flags,
                const hp::QCollection<dim - 1> &quadrature) const override;
 
  // documentation can be found in Mapping::get_subface_data()
  virtual std::unique_ptr<typename Mapping<dim, spacedim>::InternalDataBase>
  get_subface_data(const UpdateFlags          flags,
                   const Quadrature<dim - 1> &quadrature) const override;
 
  // documentation can be found in Mapping::fill_fe_values()
  virtual CellSimilarity::Similarity
  fill_fe_values(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const CellSimilarity::Similarity                            cell_similarity,
    const Quadrature<dim>                                      &quadrature,
    const typename Mapping<dim, spacedim>::InternalDataBase    &internal_data,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const override;
 
  using Mapping<dim, spacedim>::fill_fe_face_values;
 
  // documentation can be found in Mapping::fill_fe_face_values()
  virtual void
  fill_fe_face_values(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const unsigned int                                          face_no,
    const hp::QCollection<dim - 1>                             &quadrature,
    const typename Mapping<dim, spacedim>::InternalDataBase    &internal_data,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const override;
 
  // documentation can be found in Mapping::fill_fe_subface_values()
  virtual void
  fill_fe_subface_values(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const unsigned int                                          face_no,
    const unsigned int                                          subface_no,
    const Quadrature<dim - 1>                                  &quadrature,
    const typename Mapping<dim, spacedim>::InternalDataBase    &internal_data,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const override;

 
protected:
  const std::unique_ptr<FiniteElement<dim, spacedim>> fe;

  const unsigned int polynomial_degree;

  virtual boost::container::small_vector<Point<spacedim>, 200>
  compute_mapping_support_points(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell) const;
 
private:
  Table<2, double> mapping_support_point_weights;
};
 
 

 
/*----------------------------------------------------------------------*/
 
#ifndef DOXYGEN
 
template <int dim, int spacedim>
inline const double &
MappingFE<dim, spacedim>::InternalData::shape(const unsigned int qpoint,
                                              const unsigned int shape_nr) const
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr, shape_values.size());
  return shape_values[qpoint * n_shape_functions + shape_nr];
}
 
 
 
template <int dim, int spacedim>
inline double &
MappingFE<dim, spacedim>::InternalData::shape(const unsigned int qpoint,
                                              const unsigned int shape_nr)
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr, shape_values.size());
  return shape_values[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline const Tensor<1, dim> &
MappingFE<dim, spacedim>::InternalData::derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr) const
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_derivatives.size());
  return shape_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
 
template <int dim, int spacedim>
inline Tensor<1, dim> &
MappingFE<dim, spacedim>::InternalData::derivative(const unsigned int qpoint,
                                                   const unsigned int shape_nr)
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_derivatives.size());
  return shape_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline const Tensor<2, dim> &
MappingFE<dim, spacedim>::InternalData::second_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr) const
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_second_derivatives.size());
  return shape_second_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline Tensor<2, dim> &
MappingFE<dim, spacedim>::InternalData::second_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr)
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_second_derivatives.size());
  return shape_second_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
template <int dim, int spacedim>
inline const Tensor<3, dim> &
MappingFE<dim, spacedim>::InternalData::third_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr) const
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_third_derivatives.size());
  return shape_third_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline Tensor<3, dim> &
MappingFE<dim, spacedim>::InternalData::third_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr)
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_third_derivatives.size());
  return shape_third_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline const Tensor<4, dim> &
MappingFE<dim, spacedim>::InternalData::fourth_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr) const
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_fourth_derivatives.size());
  return shape_fourth_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
template <int dim, int spacedim>
inline Tensor<4, dim> &
MappingFE<dim, spacedim>::InternalData::fourth_derivative(
  const unsigned int qpoint,
  const unsigned int shape_nr)
{
  AssertIndexRange(qpoint * n_shape_functions + shape_nr,
                   shape_fourth_derivatives.size());
  return shape_fourth_derivatives[qpoint * n_shape_functions + shape_nr];
}
 
 
 
template <int dim, int spacedim>
inline bool
MappingFE<dim, spacedim>::preserves_vertex_locations() const
{
  return true;
}
 
 
 
#endif // DOXYGEN
 
/* -------------- declaration of explicit specializations ------------- */
 
 
DEAL_II_NAMESPACE_CLOSE
 
#endif