function_derivative.h

// ---------------------------------------------------------------------
//
// Copyright (C) 2000 - 2018 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.md at
// the top level directory of deal.II.
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#ifndef dealii_function_derivative_h
#define dealii_function_derivative_h

#include <deal.II/base/config.h>

#include <deal.II/base/auto_derivative_function.h>
#include <deal.II/base/exceptions.h>
#include <deal.II/base/function.h>

DEAL_II_NAMESPACE_OPEN


template <int dim>
class FunctionDerivative : public AutoDerivativeFunction<dim>
{
public:
  FunctionDerivative(const Function<dim> &f,
                     const Point<dim> &   direction,
                     const double         h = 1.e-6);

  FunctionDerivative(const Function<dim> &          f,
                     const std::vector<Point<dim>> &direction,
                     const double                   h = 1.e-6);

  void
  set_formula(typename AutoDerivativeFunction<dim>::DifferenceFormula formula =
                AutoDerivativeFunction<dim>::Euler);
  void
  set_h(const double h);

  virtual double
  value(const Point<dim> &p, const unsigned int component = 0) const override;

  virtual void
  vector_value(const Point<dim> &p, Vector<double> &value) const override;

  virtual void
  value_list(const std::vector<Point<dim>> &points,
             std::vector<double> &          values,
             const unsigned int             component = 0) const override;

  std::size_t
  memory_consumption() const;

private:
  const Function<dim> &f;

  double h;

  typename AutoDerivativeFunction<dim>::DifferenceFormula formula;

  std::vector<Tensor<1, dim>> incr;
};

DEAL_II_NAMESPACE_CLOSE

#endif