auto_derivative_function.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2001 - 2026 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_auto_derivative_function_h
#define dealii_auto_derivative_function_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/function.h>
 
DEAL_II_NAMESPACE_OPEN
 
template <int dim>
class AutoDerivativeFunction : public Function<dim>
{
public:
  enum DifferenceFormula
  {
    Euler,
    UpwindEuler,
    FourthOrder
  };
 
  AutoDerivativeFunction(const double       h,
                         const unsigned int n_components = 1,
                         const double       initial_time = 0.0);
 
  virtual ~AutoDerivativeFunction() override = default;
 
  void
  set_formula(const DifferenceFormula formula = Euler);
 
  void
  set_h(const double h);
 
  virtual Tensor<1, dim>
  gradient(const Point<dim>  &p,
           const unsigned int component = 0) const override;
 
  virtual void
  vector_gradient(const Point<dim>            &p,
                  std::vector<Tensor<1, dim>> &gradients) const override;
 
  virtual void
  gradient_list(const std::vector<Point<dim>> &points,
                std::vector<Tensor<1, dim>>   &gradients,
                const unsigned int             component = 0) const override;
 
  virtual void
  vector_gradient_list(
    const std::vector<Point<dim>>            &points,
    std::vector<std::vector<Tensor<1, dim>>> &gradients) const override;
 
  static DifferenceFormula
  get_formula_of_order(const unsigned int ord);
 
 
private:
  double h;
 
  std::vector<Tensor<1, dim>> ht;
 
  DifferenceFormula formula;
};
 
 
DEAL_II_NAMESPACE_CLOSE
 
#endif