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//
// Copyright (C) 2003 - 2015 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, 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.
// The full text of the license can be found in the file LICENSE at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef dealii__fe_raviart_thomas_h
#define dealii__fe_raviart_thomas_h
#include <deal.II/base/config.h>
#include <deal.II/base/table.h>
#include <deal.II/base/polynomials_raviart_thomas.h>
#include <deal.II/base/polynomial.h>
#include <deal.II/base/tensor_product_polynomials.h>
#include <deal.II/base/geometry_info.h>
#include <deal.II/fe/fe.h>
#include <deal.II/fe/fe_poly_tensor.h>
#include <vector>
DEAL_II_NAMESPACE_OPEN
template <int dim, int spacedim> class MappingQ;
/*!@addtogroup fe */
/*@{*/
/**
* Implementation of Raviart-Thomas (RT) elements, conforming with the space
* H<sup>div</sup>. These elements generate vector fields with normal
* components continuous between mesh cells.
*
* We follow the usual definition of the degree of RT elements, which denotes
* the polynomial degree of the largest complete polynomial subspace contained
* in the RT space. Then, approximation order of the function itself is
* <i>degree+1</i>, as with usual polynomial spaces. The numbering so chosen
* implies the sequence
* @f[
* Q_{k+1}
* \stackrel{\text{grad}}{\rightarrow}
* \text{Nedelec}_k
* \stackrel{\text{curl}}{\rightarrow}
* \text{RaviartThomas}_k
* \stackrel{\text{div}}{\rightarrow}
* DGQ_{k}
* @f]
* The lowest order element is consequently FE_RaviartThomas(0).
*
* This class is not implemented for the codimension one case (<tt>spacedim !=
* dim</tt>).
*
* @todo Even if this element is implemented for two and three space
* dimensions, the definition of the node values relies on consistently
* oriented faces in 3D. Therefore, care should be taken on complicated
* meshes.
*
* <h3>Interpolation</h3>
*
* The
* @ref GlossInterpolation "interpolation"
* operators associated with the RT element are constructed such that
* interpolation and computing the divergence are commuting operations. We
* require this from interpolating arbitrary functions as well as the
* #restriction matrices. It can be achieved by two interpolation schemes,
* the simplified one in FE_RaviartThomasNodal and the original one here:
*
* <h4>Node values on edges/faces</h4>
*
* On edges or faces, the
* @ref GlossNodes "node values"
* are the moments of the normal component of the interpolated function with
* respect to the traces of the RT polynomials. Since the normal trace of the
* RT space of degree <i>k</i> on an edge/face is the space
* <i>Q<sub>k</sub></i>, the moments are taken with respect to this space.
*
* <h4>Interior node values</h4>
*
* Higher order RT spaces have interior nodes. These are moments taken with
* respect to the gradient of functions in <i>Q<sub>k</sub></i> on the cell
* (this space is the matching space for RT<sub>k</sub> in a mixed
* formulation).
*
* <h4>Generalized support points</h4>
*
* The node values above rely on integrals, which will be computed by
* quadrature rules themselves. The generalized support points are a set of
* points such that this quadrature can be performed with sufficient accuracy.
* The points needed are those of QGauss<sub>k+1</sub> on each face as well as
* QGauss<sub>k</sub> in the interior of the cell (or none for
* RT<sub>0</sub>).
*
*
* @author Guido Kanschat, 2005, based on previous Work by Wolfgang Bangerth
*/
template <int dim>
class FE_RaviartThomas
:
public FE_PolyTensor<PolynomialsRaviartThomas<dim>, dim>
{
public:
/**
* Constructor for the Raviart-Thomas element of degree @p p.
*/
FE_RaviartThomas (const unsigned int p);
/**
* Return a string that uniquely identifies a finite element. This class
* returns <tt>FE_RaviartThomas<dim>(degree)</tt>, with @p dim and @p degree
* replaced by appropriate values.
*/
virtual std::string get_name () const;
/**
* This function returns @p true, if the shape function @p shape_index has
* non-zero function values somewhere on the face @p face_index.
*
* Right now, this is only implemented for RT0 in 1D. Otherwise, returns
* always @p true.
*/
virtual bool has_support_on_face (const unsigned int shape_index,
const unsigned int face_index) const;
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<double> &values) const;
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<Vector<double> > &values,
unsigned int offset = 0) const;
virtual void interpolate(
std::vector<double> &local_dofs,
const VectorSlice<const std::vector<std::vector<double> > > &values) const;
/**
* Returns a list of constant modes of the element. This method is currently
* not correctly implemented because it returns ones for all components.
*/
virtual std::pair<Table<2,bool>, std::vector<unsigned int> >
get_constant_modes () const;
virtual std::size_t memory_consumption () const;
virtual FiniteElement<dim> *clone() const;
private:
/**
* Only for internal use. Its full name is @p get_dofs_per_object_vector
* function and it creates the @p dofs_per_object vector that is needed
* within the constructor to be passed to the constructor of @p
* FiniteElementData.
*/
static std::vector<unsigned int>
get_dpo_vector (const unsigned int degree);
/**
* Initialize the @p generalized_support_points field of the FiniteElement
* class and fill the tables with interpolation weights (#boundary_weights
* and #interior_weights). Called from the constructor.
*/
void initialize_support_points (const unsigned int rt_degree);
/**
* Initialize the interpolation from functions on refined mesh cells onto
* the father cell. According to the philosophy of the Raviart-Thomas
* element, this restriction operator preserves the divergence of a function
* weakly.
*/
void initialize_restriction ();
/**
* These are the factors multiplied to a function in the
* #generalized_face_support_points when computing the integration. They are
* organized such that there is one row for each generalized face support
* point and one column for each degree of freedom on the face.
*
* See the
* @ref GlossGeneralizedSupport "glossary entry on generalized support points"
* for more information.
*/
Table<2, double> boundary_weights;
/**
* Precomputed factors for interpolation of interior degrees of freedom. The
* rationale for this Table is the same as for #boundary_weights. Only, this
* table has a third coordinate for the space direction of the component
* evaluated.
*/
Table<3, double> interior_weights;
/**
* Allow access from other dimensions.
*/
template <int dim1> friend class FE_RaviartThomas;
};
/**
* The Raviart-Thomas elements with node functionals defined as point values
* in Gauss points.
*
* <h3>Description of node values</h3>
*
* For this Raviart-Thomas element, the node values are not cell and face
* moments with respect to certain polynomials, but the values in quadrature
* points. Following the general scheme for numbering degrees of freedom, the
* node values on edges are first, edge by edge, according to the natural
* ordering of the edges of a cell. The interior degrees of freedom are last.
*
* For an RT-element of degree <i>k</i>, we choose <i>(k+1)<sup>d-1</sup></i>
* Gauss points on each face. These points are ordered lexicographically with
* respect to the orientation of the face. This way, the normal component
* which is in <i>Q<sub>k</sub></i> is uniquely determined. Furthermore, since
* this Gauss-formula is exact on <i>Q<sub>2k+1</sub></i>, these node values
* correspond to the exact integration of the moments of the RT-space.
*
* In the interior of the cells, the moments are with respect to an
* anisotropic <i>Q<sub>k</sub></i> space, where the test functions are one
* degree lower in the direction corresponding to the vector component under
* consideration. This is emulated by using an anisotropic Gauss formula for
* integration.
*
* @todo The current implementation is for Cartesian meshes only. You must use
* MappingCartesian.
*
* @todo Even if this element is implemented for two and three space
* dimensions, the definition of the node values relies on consistently
* oriented faces in 3D. Therefore, care should be taken on complicated
* meshes.
*
* @note The degree stored in the member variable
* FiniteElementData<dim>::degree is higher by one than the constructor
* argument!
*
* @author Guido Kanschat, 2005, Zhu Liang, 2008
*/
template <int dim>
class FE_RaviartThomasNodal
:
public FE_PolyTensor<PolynomialsRaviartThomas<dim>, dim>
{
public:
/**
* Constructor for the Raviart-Thomas element of degree @p p.
*/
FE_RaviartThomasNodal (const unsigned int p);
/**
* Return a string that uniquely identifies a finite element. This class
* returns <tt>FE_RaviartThomasNodal<dim>(degree)</tt>, with @p dim and @p
* degree replaced by appropriate values.
*/
virtual std::string get_name () const;
virtual FiniteElement<dim> *clone () const;
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<double> &values) const;
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<Vector<double> > &values,
unsigned int offset = 0) const;
virtual void interpolate(
std::vector<double> &local_dofs,
const VectorSlice<const std::vector<std::vector<double> > > &values) const;
virtual void get_face_interpolation_matrix (const FiniteElement<dim> &source,
FullMatrix<double> &matrix) const;
virtual void get_subface_interpolation_matrix (const FiniteElement<dim> &source,
const unsigned int subface,
FullMatrix<double> &matrix) const;
virtual bool hp_constraints_are_implemented () const;
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_vertex_dof_identities (const FiniteElement<dim> &fe_other) const;
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_line_dof_identities (const FiniteElement<dim> &fe_other) const;
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_quad_dof_identities (const FiniteElement<dim> &fe_other) const;
virtual FiniteElementDomination::Domination
compare_for_face_domination (const FiniteElement<dim> &fe_other) const;
private:
/**
* Only for internal use. Its full name is @p get_dofs_per_object_vector
* function and it creates the @p dofs_per_object vector that is needed
* within the constructor to be passed to the constructor of @p
* FiniteElementData.
*/
static std::vector<unsigned int>
get_dpo_vector (const unsigned int degree);
/**
* Compute the vector used for the @p restriction_is_additive field passed
* to the base class's constructor.
*/
static std::vector<bool>
get_ria_vector (const unsigned int degree);
/**
* This function returns @p true, if the shape function @p shape_index has
* non-zero function values somewhere on the face @p face_index.
*
* Right now, this is only implemented for RT0 in 1D. Otherwise, returns
* always @p true.
*/
virtual bool has_support_on_face (const unsigned int shape_index,
const unsigned int face_index) const;
/**
* Initialize the FiniteElement<dim>::generalized_support_points and
* FiniteElement<dim>::generalized_face_support_points fields. Called from
* the constructor.
*
* See the
* @ref GlossGeneralizedSupport "glossary entry on generalized support points"
* for more information.
*/
void initialize_support_points (const unsigned int rt_degree);
};
/*@}*/
/* -------------- declaration of explicit specializations ------------- */
#ifndef DOXYGEN
template <>
void
FE_RaviartThomas<1>::initialize_restriction();
#endif // DOXYGEN
DEAL_II_NAMESPACE_CLOSE
#endif
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