/usr/include/deal.II/base/tensor_function.h is in libdeal.ii-dev 8.4.2-2+b1.
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//
// Copyright (C) 1999 - 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__tensor_function_h
#define dealii__tensor_function_h
#include <deal.II/base/config.h>
#include <deal.II/base/exceptions.h>
#include <deal.II/base/subscriptor.h>
#include <deal.II/base/smartpointer.h>
#include <deal.II/base/function.h>
#include <deal.II/base/point.h>
#include <deal.II/base/function_time.h>
#include <vector>
DEAL_II_NAMESPACE_OPEN
/**
* This class is a model for a tensor valued function. The interface of the
* class is mostly the same as that for the Function class, with the exception
* that it does not support vector-valued functions with several components,
* but that the return type is always tensor-valued. The returned values of
* the evaluation of objects of this type are always whole tensors, while for
* the <tt>Function</tt> class, one can ask for a specific component only, or
* use the <tt>vector_value</tt> function, which however does not return the
* value, but rather writes it into the address provided by its second
* argument. The reason for the different behaviour of the classes is that in
* the case of tensor valued functions, the size of the argument is known to
* the compiler a priori, such that the correct amount of memory can be
* allocated on the stack for the return value; on the other hand, for the
* vector valued functions, the size is not known to the compiler, so memory
* has to be allocated on the heap, resulting in relatively expensive copy
* operations. One can therefore consider this class a specialization of the
* <tt>Function</tt> class for which the size is known. An additional benefit
* is that tensors of arbitrary rank can be returned, not only vectors, as for
* them the size can be determined similarly simply.
*
* @ingroup functions
* @author Guido Kanschat, 1999
*/
template <int rank, int dim, typename Number=double>
class TensorFunction : public FunctionTime<Number>,
public Subscriptor
{
public:
/**
* Define typedefs for the return types of the <tt>value</tt> functions.
*/
typedef Tensor<rank,dim,Number> value_type;
typedef Tensor<rank+1,dim,Number> gradient_type;
/**
* Constructor. May take an initial value for the time variable, which
* defaults to zero.
*/
TensorFunction (const Number initial_time = Number(0.0));
/**
* Virtual destructor; absolutely necessary in this case, as classes are
* usually not used by their true type, but rather through pointers to this
* base class.
*/
virtual ~TensorFunction ();
/**
* Return the value of the function at the given point.
*/
virtual value_type value (const Point<dim> &p) const;
/**
* Set <tt>values</tt> to the point values of the function at the
* <tt>points</tt>. It is assumed that <tt>values</tt> already has the
* right size, i.e. the same size as the <tt>points</tt> array.
*/
virtual void value_list (const std::vector<Point<dim> > &points,
std::vector<value_type> &values) const;
/**
* Return the gradient of the function at the given point.
*/
virtual gradient_type gradient (const Point<dim> &p) const;
/**
* Set <tt>gradients</tt> to the gradients of the function at the
* <tt>points</tt>. It is assumed that <tt>values</tt> already has the
* right size, i.e. the same size as the <tt>points</tt> array.
*/
virtual void gradient_list (const std::vector<Point<dim> > &points,
std::vector<gradient_type> &gradients) const;
};
/**
* Provide a tensor valued function which always returns a constant tensor
* value. Obviously, all derivates of this function are zero.
*
* @ingroup functions
* @author Matthias Maier, 2013
*/
template <int rank, int dim, typename Number=double>
class ConstantTensorFunction : public TensorFunction<rank, dim, Number>
{
public:
/**
* Constructor; takes the constant tensor value as an argument. The
* reference value is copied internally.
*
* An initial value for the time variable may be specified, otherwise it
* defaults to zero.
*/
ConstantTensorFunction (const dealii::Tensor<rank, dim, Number> &value,
const Number initial_time = 0.0);
virtual ~ConstantTensorFunction ();
virtual typename dealii::TensorFunction<rank, dim, Number>::value_type value (const Point<dim> &p) const;
virtual void value_list (const std::vector<Point<dim> > &points,
std::vector<typename dealii::TensorFunction<rank, dim, Number>::value_type> &values) const;
virtual typename dealii::TensorFunction<rank, dim, Number>::gradient_type gradient (const Point<dim> &p) const;
virtual void gradient_list (const std::vector<Point<dim> > &points,
std::vector<typename dealii::TensorFunction<rank, dim, Number>::gradient_type> &gradients) const;
private:
const dealii::Tensor<rank, dim, Number> _value;
};
/**
* Provide a tensor valued function which always returns zero. Obviously, all
* derivates of this function are zero.
*
* @ingroup functions
* @author Matthias Maier, 2013
*/
template <int rank, int dim, typename Number=double>
class ZeroTensorFunction : public ConstantTensorFunction<rank, dim, Number>
{
public:
/**
* Constructor.
*
* An initial value for the time variable may be specified, otherwise it
* defaults to zero.
*/
ZeroTensorFunction (const Number initial_time = 0.0);
};
DEAL_II_NAMESPACE_CLOSE
#endif
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