mapping_p1.h

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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2025 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Part of the source code is dual licensed under Apache-2.0 WITH
// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
// governing the source code and code contributions can be found in
// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
//
// ------------------------------------------------------------------------
 
#ifndef dealii_mapping_p1_h
#define dealii_mapping_p1_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/qprojector.h>
 
#include <deal.II/fe/mapping.h>
 
#include <cmath>
 
 
DEAL_II_NAMESPACE_OPEN


template <int dim, int spacedim = dim>
class MappingP1 : public Mapping<dim, spacedim>
{
public:
  MappingP1() = default;
 
  virtual std::unique_ptr<Mapping<dim, spacedim>>
  clone() const override;

  virtual bool
  preserves_vertex_locations() const override;

  virtual bool
  is_compatible_with(const ReferenceCell &reference_cell) const override;

 
  virtual Point<spacedim>
  transform_unit_to_real_cell(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const Point<dim> &p) const override;
 
  virtual Point<dim>
  transform_real_to_unit_cell(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const Point<spacedim> &p) const override;
 
  virtual void
  transform_points_real_to_unit_cell(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const ArrayView<const Point<spacedim>>                     &real_points,
    const ArrayView<Point<dim>> &unit_points) const override;


 
  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;
 
  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;
 
  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;
 
  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;
 
  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;


  void
  fill_mapping_data_for_generic_points(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const ArrayView<const Point<dim>>                          &unit_points,
    const UpdateFlags                                           update_flags,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const;


  class InternalData : public Mapping<dim, spacedim>::InternalDataBase
  {
  public:
    InternalData(const ArrayView<const Point<dim>> &quadrature_points);

    InternalData(const Quadrature<dim> &quadrature);
 
    virtual void
    reinit(const UpdateFlags      update_flags,
           const Quadrature<dim> &quadrature) override;

    virtual std::size_t
    memory_consumption() const override;

    mutable Tensor<1, spacedim> affine_component;

    mutable DerivativeForm<1, dim, spacedim> linear_component;

    mutable DerivativeForm<1, dim, spacedim> covariant;

    mutable double determinant;

    Quadrature<dim> quadrature;
  };
 
private:
  virtual UpdateFlags
  requires_update_flags(const UpdateFlags update_flags) const override;
 
  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;
 
  virtual std::unique_ptr<typename Mapping<dim, spacedim>::InternalDataBase>
  get_face_data(const UpdateFlags               flags,
                const hp::QCollection<dim - 1> &quadrature) const override;
 
  virtual std::unique_ptr<typename Mapping<dim, spacedim>::InternalDataBase>
  get_subface_data(const UpdateFlags          flags,
                   const Quadrature<dim - 1> &quadrature) const override;
 
  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;
 
  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;
 
  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;


  void
  update_transformation(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const InternalData                                         &data) const;

  void
  transform_quadrature_points(
    const typename Triangulation<dim, spacedim>::cell_iterator &cell,
    const InternalData                                         &data,
    const typename QProjector<dim>::DataSetDescriptor          &offset,
    std::vector<Point<spacedim>> &quadrature_points) const;

  void
  maybe_update_normal_vectors(
    const unsigned int                face_no,
    const InternalData               &data,
    std::vector<Tensor<1, spacedim>> &normal_vectors) const;

  void
  maybe_update_jacobian_derivatives(
    const InternalData              &data,
    const CellSimilarity::Similarity cell_similarity,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const;

  void
  maybe_update_jacobians(
    const InternalData              &data,
    const CellSimilarity::Similarity cell_similarity,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const;

  void
  maybe_update_inverse_jacobians(
    const InternalData              &data,
    const CellSimilarity::Similarity cell_similarity,
    internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
      &output_data) const;
};

 
DEAL_II_NAMESPACE_CLOSE
 
#endif