mapping_q1_eulerian.cc

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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2001 - 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.
//
// ------------------------------------------------------------------------
 
 
#include <deal.II/dofs/dof_accessor.h>
#include <deal.II/dofs/dof_handler.h>
 
#include <deal.II/fe/fe.h>
#include <deal.II/fe/mapping_q1_eulerian.h>
 
#include <deal.II/grid/tria_iterator.h>
 
#include <deal.II/lac/block_vector.h>
#include <deal.II/lac/la_parallel_block_vector.h>
#include <deal.II/lac/la_parallel_vector.h>
#include <deal.II/lac/petsc_block_vector.h>
#include <deal.II/lac/petsc_vector.h>
#include <deal.II/lac/trilinos_parallel_block_vector.h>
#include <deal.II/lac/trilinos_vector.h>
#include <deal.II/lac/vector.h>
 
#include <boost/container/small_vector.hpp>
 
#include <array>
#include <memory>
 
 
DEAL_II_NAMESPACE_OPEN
 
 
template <int dim, typename VectorType, int spacedim>
MappingQ1Eulerian<dim, VectorType, spacedim>::MappingQ1Eulerian(
  const DoFHandler<dim, spacedim> &shiftmap_dof_handler,
  const VectorType                &euler_transform_vectors)
  : MappingQ<dim, spacedim>(1)
  , euler_transform_vectors(&euler_transform_vectors)
  , shiftmap_dof_handler(&shiftmap_dof_handler)
{}
 
 
 
template <int dim, typename VectorType, int spacedim>
boost::container::small_vector<Point<spacedim>,
#ifndef _MSC_VER
                               ReferenceCells::max_n_vertices<dim>()
#else
                               GeometryInfo<dim>::vertices_per_cell
#endif
                               >
MappingQ1Eulerian<dim, VectorType, spacedim>::get_vertices(
  const typename Triangulation<dim, spacedim>::cell_iterator &cell) const
{
  boost::container::small_vector<Point<spacedim>,
#ifndef _MSC_VER
                                 ReferenceCells::max_n_vertices<dim>()
#else
                                 GeometryInfo<dim>::vertices_per_cell
#endif
                                 >
    vertices(cell->n_vertices());
  // The assertions can not be in the constructor, since this would
  // require to call dof_handler.distribute_dofs(fe) *before* the mapping
  // object is constructed, which is not necessarily what we want.
 
  // TODO: Only one of these two assertions should be relevant
  AssertDimension(spacedim, shiftmap_dof_handler->get_fe().n_dofs_per_vertex());
  AssertDimension(shiftmap_dof_handler->get_fe(0).n_components(), spacedim);
 
  AssertDimension(shiftmap_dof_handler->n_dofs(),
                  euler_transform_vectors->size());
 
  // cast the Triangulation<dim>::cell_iterator into a
  // DoFHandler<dim>::cell_iterator which is necessary for access to
  // DoFCellAccessor::get_dof_values()
  typename DoFHandler<dim, spacedim>::cell_iterator dof_cell(
    *cell, shiftmap_dof_handler);
 
  // We require the cell to be active since we can only then get nodal
  // values for the shifts
  Assert(dof_cell->is_active() == true, ExcInactiveCell());
 
  // now get the values of the shift vectors at the vertices
  Vector<typename VectorType::value_type> mapping_values(
    shiftmap_dof_handler->get_fe().n_dofs_per_cell());
  dof_cell->get_dof_values(*euler_transform_vectors, mapping_values);
 
  for (const unsigned int i : GeometryInfo<dim>::vertex_indices())
    {
      Point<spacedim> shift_vector;
 
      // pick out the value of the shift vector at the present
      // vertex. since vertex dofs are always numbered first, we can
      // access them easily
      for (unsigned int j = 0; j < spacedim; ++j)
        shift_vector[j] = mapping_values(i * spacedim + j);
 
      // compute new support point by old (reference) value and added
      // shift
      vertices[i] = cell->vertex(i) + shift_vector;
    }
  return vertices;
}
 
 
 
template <int dim, typename VectorType, int spacedim>
std::vector<Point<spacedim>>
MappingQ1Eulerian<dim, VectorType, spacedim>::compute_mapping_support_points(
  const typename Triangulation<dim, spacedim>::cell_iterator &cell) const
{
  const auto vertices = this->get_vertices(cell);
 
  std::vector<Point<spacedim>> a(GeometryInfo<dim>::vertices_per_cell);
  for (const unsigned int i : GeometryInfo<dim>::vertex_indices())
    a[i] = vertices[i];
 
  return a;
}
 
 
 
template <int dim, typename VectorType, int spacedim>
std::unique_ptr<Mapping<dim, spacedim>>
MappingQ1Eulerian<dim, VectorType, spacedim>::clone() const
{
  return std::make_unique<MappingQ1Eulerian<dim, VectorType, spacedim>>(*this);
}
 
 
 
template <int dim, typename VectorType, int spacedim>
CellSimilarity::Similarity
MappingQ1Eulerian<dim, VectorType, spacedim>::fill_fe_values(
  const typename Triangulation<dim, spacedim>::cell_iterator &cell,
  const CellSimilarity::Similarity,
  const Quadrature<dim>                                   &quadrature,
  const typename Mapping<dim, spacedim>::InternalDataBase &internal_data,
  internal::FEValuesImplementation::MappingRelatedData<dim, spacedim>
    &output_data) const
{
  // call the function of the base class, but ignoring
  // any potentially detected cell similarity between
  // the current and the previous cell
  MappingQ<dim, spacedim>::fill_fe_values(cell,
                                          CellSimilarity::invalid_next_cell,
                                          quadrature,
                                          internal_data,
                                          output_data);
  // also return the updated flag since any detected
  // similarity wasn't based on the mapped field, but
  // the original vertices which are meaningless
  return CellSimilarity::invalid_next_cell;
}
 
 
 
// explicit instantiations
#include "fe/mapping_q1_eulerian.inst"
 
 
DEAL_II_NAMESPACE_CLOSE