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//
// Copyright (C) 2002 - 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_nedelec_h
#define dealii__fe_nedelec_h
#include <deal.II/base/config.h>
#include <deal.II/base/table.h>
#include <deal.II/base/tensor.h>
#include <deal.II/base/tensor.h>
#include <deal.II/base/polynomials_nedelec.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/base/thread_management.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 */
/*@{*/
/**
* @warning Several aspects of the implementation are experimental. For the
* moment, it is safe to use the element on globally refined meshes with
* consistent orientation of faces. See the todo entries below for more
* detailed caveats.
*
* Implementation of Nédélec elements, conforming with the space
* H<sup>curl</sup>. These elements generate vector fields with tangential
* components continuous between mesh cells.
*
* We follow the convention that the degree of Nédélec elements
* denotes the polynomial degree of the largest complete polynomial subspace
* contained in the Nédélec space. This leads to the
* consistently numbered sequence of spaces
* @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]
* Consequently, approximation order of the Nédélec space equals the value
* <i>degree</i> given to the constructor. In this scheme, the lowest order
* element would be created by the call FE_Nedelec<dim>(0). Note that this
* follows the convention of Brezzi and Raviart, though not the one used in
* the original paper by Nédélec.
*
* 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 Nédélec element are constructed
* such that interpolation and computing the curl are commuting operations on
* rectangular mesh cells. We require this from interpolating arbitrary
* functions as well as the #restriction matrices.
*
* <h4>Node values</h4>
*
* The
* @ref GlossNodes "node values"
* for an element of degree <i>k</i> on the reference cell are:
* <ol>
* <li> On edges: the moments of the tangential component with respect to
* polynomials of degree <i>k</i>.
* <li> On faces: the moments of the tangential components with respect to
* <tt>dim</tt>-1 dimensional FE_Nedelec polynomials of degree <i>k</i>-1.
* <li> In cells: the moments with respect to gradients of polynomials in FE_Q
* of degree <i>k</i>.
* </ol>
*
* <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 edge and
* QGauss<sub>k+2</sub> on each face and in the interior of the cell (or none
* for N<sub>1</sub>).
*
* @author Markus Bürg
* @date 2009, 2010, 2011
*/
template <int dim>
class FE_Nedelec : public FE_PolyTensor<PolynomialsNedelec<dim>, dim>
{
public:
/**
* Constructor for the Nédélec element of degree @p p.
*/
FE_Nedelec (const unsigned int p);
/**
* Return a string that uniquely identifies a finite element. This class
* returns <tt>FE_Nedelec<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.
*/
virtual bool has_support_on_face (const unsigned int shape_index,
const unsigned int face_index) const;
/**
* Return whether this element implements its hanging node constraints in
* the new way, which has to be used to make elements "hp compatible".
*
* For the <tt>FE_Nedelec</tt> class the result is always true (independent
* of the degree of the element), as it implements the complete set of
* functions necessary for hp capability.
*/
virtual bool hp_constraints_are_implemented () const;
/**
* Return whether this element dominates the one, which is given as
* argument.
*/
virtual FiniteElementDomination::Domination
compare_for_face_domination (const FiniteElement<dim> &fe_other) const;
/**
* If, on a vertex, several finite elements are active, the hp code first
* assigns the degrees of freedom of each of these FEs different global
* indices. It then calls this function to find out which of them should get
* identical values, and consequently can receive the same global DoF index.
* This function therefore returns a list of identities between DoFs of the
* present finite element object with the DoFs of @p fe_other, which is a
* reference to a finite element object representing one of the other finite
* elements active on this particular vertex. The function computes which of
* the degrees of freedom of the two finite element objects are equivalent,
* both numbered between zero and the corresponding value of dofs_per_vertex
* of the two finite elements. The first index of each pair denotes one of
* the vertex dofs of the present element, whereas the second is the
* corresponding index of the other finite element.
*/
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_vertex_dof_identities (const FiniteElement<dim> &fe_other) const;
/**
* Same as hp_vertex_dof_indices(), except that the function treats degrees
* of freedom on lines.
*/
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_line_dof_identities (const FiniteElement<dim> &fe_other) const;
/**
* Same as hp_vertex_dof_indices(), except that the function treats degrees
* of freedom on lines.
*/
virtual std::vector<std::pair<unsigned int, unsigned int> >
hp_quad_dof_identities (const FiniteElement<dim> &fe_other) const;
/**
* Return the matrix interpolating from a face of one element to the face of
* the neighboring element. The size of the matrix is then
* <tt>source.dofs_per_face</tt> times <tt>this->dofs_per_face</tt>.
*
* Derived elements will have to implement this function. They may only
* provide interpolation matrices for certain source finite elements, for
* example those from the same family. If they don't implement interpolation
* from a given element, then they must throw an exception of type
* <tt>FiniteElement<dim>::ExcInterpolationNotImplemented</tt>.
*/
virtual void
get_face_interpolation_matrix (const FiniteElement<dim> &source,
FullMatrix<double> &matrix) const;
/**
* Return the matrix interpolating from a face of one element to the subface
* of the neighboring element. The size of the matrix is then
* <tt>source.dofs_per_face</tt> times <tt>this->dofs_per_face</tt>.
*
* Derived elements will have to implement this function. They may only
* provide interpolation matrices for certain source finite elements, for
* example those from the same family. If they don't implement interpolation
* from a given element, then they must throw an exception of type
* <tt>ExcInterpolationNotImplemented</tt>.
*/
virtual void
get_subface_interpolation_matrix (const FiniteElement<dim> &source,
const unsigned int subface,
FullMatrix<double> &matrix) const;
/**
* Projection from a fine grid space onto a coarse grid space. If this
* projection operator is associated with a matrix @p P, then the
* restriction of this matrix @p P_i to a single child cell is returned
* here.
*
* The matrix @p P is the concatenation or the sum of the cell matrices @p
* P_i, depending on the #restriction_is_additive_flags. This distinguishes
* interpolation (concatenation) and projection with respect to scalar
* products (summation).
*
* Row and column indices are related to coarse grid and fine grid spaces,
* respectively, consistent with the definition of the associated operator.
*/
virtual const FullMatrix<double> &
get_restriction_matrix (const unsigned int child,
const RefinementCase<dim> &refinement_case=RefinementCase<dim>::isotropic_refinement) const;
/**
* Embedding matrix between grids.
*
* The identity operator from a coarse grid space into a fine grid space is
* associated with a matrix @p P. The restriction of this matrix @p P_i to a
* single child cell is returned here.
*
* The matrix @p P is the concatenation, not the sum of the cell matrices @p
* P_i. That is, if the same non-zero entry <tt>j,k</tt> exists in in two
* different child matrices @p P_i, the value should be the same in both
* matrices and it is copied into the matrix @p P only once.
*
* Row and column indices are related to fine grid and coarse grid spaces,
* respectively, consistent with the definition of the associated operator.
*
* These matrices are used by routines assembling the prolongation matrix
* for multi-level methods. Upon assembling the transfer matrix between
* cells using this matrix array, zero elements in the prolongation matrix
* are discarded and will not fill up the transfer matrix.
*/
virtual const FullMatrix<double> &
get_prolongation_matrix (const unsigned int child,
const RefinementCase<dim> &refinement_case=RefinementCase<dim>::isotropic_refinement) 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.
*/
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.
*
* If the optional argument <tt>dg</tt> is true, the vector returned will
* have all degrees of freedom assigned to the cell, none on the faces and
* edges.
*/
static std::vector<unsigned int>
get_dpo_vector (const unsigned int degree, bool dg=false);
/**
* 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 degree);
/**
* Initialize the interpolation from functions on refined mesh cells onto
* the father cell. According to the philosophy of the Nédélec element,
* this restriction operator preserves the curl 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.
*
* See the
* @ref GlossGeneralizedSupport "glossary entry on generalized support points"
* for more information.
*/
Table<2, double> boundary_weights;
/*
* Mutex for protecting initialization of restriction and embedding matrix.
*/
mutable Threads::Mutex mutex;
/**
* Allow access from other dimensions.
*/
template <int dim1> friend class FE_Nedelec;
};
/* -------------- declaration of explicit specializations ------------- */
#ifndef DOXYGEN
template <>
void
FE_Nedelec<1>::initialize_restriction();
#endif // DOXYGEN
/*@}*/
DEAL_II_NAMESPACE_CLOSE
#endif
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