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// $Id: fe_q_dg0.h 31527 2013-11-03 09:58:45Z maier $
//
// Copyright (C) 2012 - 2013 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 __deal2__fe_q_dg0_h
#define __deal2__fe_q_dg0_h
#include <deal.II/base/config.h>
#include <deal.II/base/tensor_product_polynomials_const.h>
#include <deal.II/fe/fe_q_base.h>
DEAL_II_NAMESPACE_OPEN
/*!@addtogroup fe */
/*@{*/
/**
* Implementation of a scalar Lagrange finite element @p Qp+DG0 that yields the
* finite element space of continuous, piecewise polynomials of degree @p p in
* each coordinate direction plus the space of locally constant functions.
* This class is realized using tensor product polynomials based on equidistant
* or given support points.
*
* The standard constructor of this class takes the degree @p p of this finite
* element. Alternatively, it can take a quadrature formula @p points defining
* the support points of the Lagrange interpolation in one coordinate direction.
*
* For more information about the <tt>spacedim</tt> template parameter check
* the documentation of FiniteElement or the one of Triangulation.
*
* For more information regarding this element see:
* Boffi, D., et al. "Local Mass Conservation of Stokes Finite Elements."
* Journal of Scientific Computing (2012): 1-18.
*
* <h3>Implementation</h3>
*
* The constructor creates a TensorProductPolynomials object that includes the
* tensor product of @p LagrangeEquidistant polynomials of degree @p p plus the
* locally constant function. This @p TensorProductPolynomialsConst object
* provides all values and derivatives of the shape functions. In case a
* quadrature rule is given, the constructor creates a
* TensorProductPolynomialsConst object that includes the tensor product of @p
* Lagrange polynomials with the support points from @p points and a locally
* constant function.
*
* Furthermore the constructor fills the @p interface_constrains, the @p
* prolongation (embedding) and the @p restriction matrices.
*
* <h3>Numbering of the degrees of freedom (DoFs)</h3>
*
* The original ordering of the shape functions represented by the
* TensorProductPolynomialsConst is a tensor product
* numbering. However, the shape functions on a cell are renumbered
* beginning with the shape functions whose support points are at the
* vertices, then on the line, on the quads, and finally (for 3d) on
* the hexes. Finally there is a support point for the discontinuous shape
* function in the middle of the cell. To be explicit, these numberings are
* listed in the following:
*
* <h4>Q1 elements</h4>
* <ul>
* <li> 1D case:
* @verbatim
* 0---2---1
* @endverbatim
*
* <li> 2D case:
* @verbatim
* 2-------3
* | |
* | 5 |
* | |
* 0-------1
* @endverbatim
*
* <li> 3D case:
* @verbatim
* 6-------7 6-------7
* /| | / /|
* / | | / / |
* / | | / / |
* 4 | 8 | 4-------5 |
* | 2-------3 | | 3
* | / / | | /
* | / / | | /
* |/ / | |/
* 0-------1 0-------1
* @endverbatim
*
* The respective coordinate values of the support points of the degrees
* of freedom are as follows:
* <ul>
* <li> Index 0: <tt>[ 0, 0, 0]</tt>;
* <li> Index 1: <tt>[ 1, 0, 0]</tt>;
* <li> Index 2: <tt>[ 0, 1, 0]</tt>;
* <li> Index 3: <tt>[ 1, 1, 0]</tt>;
* <li> Index 4: <tt>[ 0, 0, 1]</tt>;
* <li> Index 5: <tt>[ 1, 0, 1]</tt>;
* <li> Index 6: <tt>[ 0, 1, 1]</tt>;
* <li> Index 7: <tt>[ 1, 1, 1]</tt>;
* <li> Index 8: <tt>[1/2, 1/2, 1/2]</tt>;
* </ul>
* </ul>
* <h4>Q2 elements</h4>
* <ul>
* <li> 1D case:
* @verbatim
* 0---2---1
* @endverbatim
* Index 3 has the same coordinates as index 2
*
* <li> 2D case:
* @verbatim
* 2---7---3
* | |
* 4 8 5
* | |
* 0---6---1
* @endverbatim
* Index 9 has the same coordinates as index 2
*
* <li> 3D case:
* @verbatim
* 6--15---7 6--15---7
* /| | / /|
* 12 | 19 12 1319
* / 18 | / / |
* 4 | | 4---14--5 |
* | 2---11--3 | | 3
* | / / | 17 /
* 16 8 9 16 | 9
* |/ / | |/
* 0---10--1 0---8---1
*
* *-------* *-------*
* /| | / /|
* / | 23 | / 25 / |
* / | | / / |
* * | | *-------* |
* |20 *-------* | |21 *
* | / / | 22 | /
* | / 24 / | | /
* |/ / | |/
* *-------* *-------*
* @endverbatim
* The center vertices have number 26 and 27.
*
* The respective coordinate values of the support points of the degrees
* of freedom are as follows:
* <ul>
* <li> Index 0: <tt>[0, 0, 0]</tt>;
* <li> Index 1: <tt>[1, 0, 0]</tt>;
* <li> Index 2: <tt>[0, 1, 0]</tt>;
* <li> Index 3: <tt>[1, 1, 0]</tt>;
* <li> Index 4: <tt>[0, 0, 1]</tt>;
* <li> Index 5: <tt>[1, 0, 1]</tt>;
* <li> Index 6: <tt>[0, 1, 1]</tt>;
* <li> Index 7: <tt>[1, 1, 1]</tt>;
* <li> Index 8: <tt>[0, 1/2, 0]</tt>;
* <li> Index 9: <tt>[1, 1/2, 0]</tt>;
* <li> Index 10: <tt>[1/2, 0, 0]</tt>;
* <li> Index 11: <tt>[1/2, 1, 0]</tt>;
* <li> Index 12: <tt>[0, 1/2, 1]</tt>;
* <li> Index 13: <tt>[1, 1/2, 1]</tt>;
* <li> Index 14: <tt>[1/2, 0, 1]</tt>;
* <li> Index 15: <tt>[1/2, 1, 1]</tt>;
* <li> Index 16: <tt>[0, 0, 1/2]</tt>;
* <li> Index 17: <tt>[1, 0, 1/2]</tt>;
* <li> Index 18: <tt>[0, 1, 1/2]</tt>;
* <li> Index 19: <tt>[1, 1, 1/2]</tt>;
* <li> Index 20: <tt>[0, 1/2, 1/2]</tt>;
* <li> Index 21: <tt>[1, 1/2, 1/2]</tt>;
* <li> Index 22: <tt>[1/2, 0, 1/2]</tt>;
* <li> Index 23: <tt>[1/2, 1, 1/2]</tt>;
* <li> Index 24: <tt>[1/2, 1/2, 0]</tt>;
* <li> Index 25: <tt>[1/2, 1/2, 1]</tt>;
* <li> Index 26: <tt>[1/2, 1/2, 1/2]</tt>;
* <li> Index 27: <tt>[1/2, 1/2, 1/2]</tt>;
* </ul>
* </ul>
* <h4>Q3 elements</h4>
* <ul>
* <li> 1D case:
* @verbatim
* 0--2-4-3--1
* @endverbatim
*
* <li> 2D case:
* @verbatim
* 2--10-11-3
* | |
* 5 14 15 7
* | 16 |
* 4 12 13 6
* | |
* 0--8--9--1
* @endverbatim
* </ul>
* <h4>Q4 elements</h4>
* <ul>
* <li> 1D case:
* @verbatim
* 0--2--3--4--1
* @endverbatim
* Index 5 has the same coordinates as index 3
*
* <li> 2D case:
* @verbatim
* 2--13-14-15-3
* | |
* 6 22 23 24 9
* | |
* 5 19 20 21 8
* | |
* 4 16 17 18 7
* | |
* 0--10-11-12-1
* @endverbatim
* Index 21 has the same coordinates as index 20
* </ul>
*
*/
template <int dim, int spacedim=dim>
class FE_Q_DG0 : public FE_Q_Base<TensorProductPolynomialsConst<dim>,dim,spacedim>
{
public:
/**
* Constructor for tensor product polynomials of degree @p p plus locally
* constant functions.
*/
FE_Q_DG0 (const unsigned int p);
/**
* Constructor for tensor product polynomials with support points @p points
* plus locally constant functions based on a one-dimensional quadrature
* formula. The degree of the finite element is <tt>points.size()-1</tt>.
* Note that the first point has to be 0 and the last one 1.
*/
FE_Q_DG0 (const Quadrature<1> &points);
/**
* Return a string that uniquely identifies a finite element. This class
* returns <tt>FE_Q_DG0<dim>(degree)</tt>, with @p dim and @p degree
* replaced by appropriate values.
*/
virtual std::string get_name () const;
/**
* Interpolate a set of scalar values, computed in the generalized support
* points.
*/
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<double> &values) const;
/**
* Interpolate a set of vector values, computed in the generalized support
* points.
*
* Since a finite element often only interpolates part of a vector,
* <tt>offset</tt> is used to determine the first component of the vector to
* be interpolated. Maybe consider changing your data structures to use the
* next function.
*/
virtual void interpolate(std::vector<double> &local_dofs,
const std::vector<Vector<double> > &values,
unsigned int offset = 0) const;
/**
* Interpolate a set of vector values, computed in the generalized support
* points.
*/
virtual void interpolate(
std::vector<double> &local_dofs,
const VectorSlice<const std::vector<std::vector<double> > > &values) const;
/**
* Return the matrix interpolating from the given finite element to the
* present one. The size of the matrix is then @p dofs_per_cell times
* <tt>source.dofs_per_cell</tt>.
*
* These matrices are only available if the source element is also a @p
* FE_Q_DG0 element. Otherwise, an exception of type
* FiniteElement<dim,spacedim>::ExcInterpolationNotImplemented is thrown.
*/
virtual void
get_interpolation_matrix (const FiniteElement<dim,spacedim> &source,
FullMatrix<double> &matrix) const;
/**
* Check for non-zero values on a face.
*
* This function returns @p true, if the shape function @p shape_index has
* non-zero values on the face @p face_index.
*
* Implementation of the interface in FiniteElement
*/
virtual bool has_support_on_face (const unsigned int shape_index,
const unsigned int face_index) const;
protected:
/**
* @p clone function instead of a copy constructor.
*
* This function is needed by the constructors of @p FESystem.
*/
virtual FiniteElement<dim,spacedim> *clone() const;
private:
/**
* Returns the restriction_is_additive flags.
* Only the last component is true.
*/
static std::vector<bool> get_riaf_vector(const unsigned int degree);
/**
* 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);
};
/*@}*/
DEAL_II_NAMESPACE_CLOSE
#endif
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