analytic_function.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2023 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can 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.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



#ifndef LIBMESH_ANALYTIC_FUNCTION_H
#define LIBMESH_ANALYTIC_FUNCTION_H

// Local Includes
#include "libmesh/function_base.h"

// C++ includes
#include <cstddef>

namespace libMesh
{

// Forward Declarations
template <typename T>
class DenseVector;

template <typename Output=Number>
class AnalyticFunction : public FunctionBase<Output>
{
public:

  typedef Output (*OutputFunction)(const Point & p, const Real time);

  AnalyticFunction(OutputFunction fptr);

  typedef void (*OutputVectorFunction)(DenseVector<Output> & output,
                                       const Point & p,
                                       const Real time);
  AnalyticFunction(OutputVectorFunction fptr);

  AnalyticFunction(AnalyticFunction &&) = default;
  AnalyticFunction(const AnalyticFunction &) = default;
  AnalyticFunction &operator= (const AnalyticFunction &) = default;
  AnalyticFunction &operator= (AnalyticFunction &&) = default;
  virtual ~AnalyticFunction() = default;

  OutputFunction _number_fptr;

  OutputVectorFunction _vector_fptr;

  virtual void init() override;

  virtual void clear() override;

  virtual std::unique_ptr<FunctionBase<Output>> clone() const override;

  virtual Output operator()(const Point & p, const Real time=0.) override;

  virtual void operator()(const Point & p, const Real time, DenseVector<Output> & output) override;
};

// ------------------------------------------------------------
// AnalyticFunction inline methods
template <typename Output>
inline
Output AnalyticFunction<Output>::operator()(const Point & p, const Real time)
{
  libmesh_assert(this->initialized());
  return (this->_number_fptr(p, time));
}

template <typename Output>
inline
void AnalyticFunction<Output>::operator()(const Point & p, const Real time, DenseVector<Output> & output)
{
  libmesh_assert(this->initialized());
  this->_vector_fptr(output, p, time);
  return;
}

template <typename Output>
AnalyticFunction<Output>::AnalyticFunction(OutputFunction fptr) :
  FunctionBase<Output>(),
  _number_fptr(fptr),
  _vector_fptr(nullptr)
{
  libmesh_assert(fptr);
  this->_initialized = true;
}

template <typename Output>
inline
AnalyticFunction<Output>::AnalyticFunction(OutputVectorFunction fptr) :
  FunctionBase<Output>(),
  _number_fptr(nullptr),
  _vector_fptr(fptr)
{
  libmesh_assert(fptr);
  this->_initialized = true;
}

template <typename Output>
void AnalyticFunction<Output>::init()
{
  // 双重测试
  libmesh_assert((_number_fptr != nullptr) || (_vector_fptr != nullptr));

  // 绝对准备好
  this->_initialized = true;
}

template <typename Output>
inline
void AnalyticFunction<Output>::clear()
{
  // 我们可能需要一个方法来稍后重置这些...
  _number_fptr = nullptr;
  _vector_fptr = nullptr;

  // 绝对没准备好
  this->_initialized = false;
}

template <typename Output>
inline
std::unique_ptr<FunctionBase<Output>> AnalyticFunction<Output>::clone() const
{
  return std::unique_ptr<FunctionBase<Output>>
    (_number_fptr ?
      new AnalyticFunction<Output>(_number_fptr) :
      new AnalyticFunction<Output>(_vector_fptr));
}

} // namespace libMesh

#endif // LIBMESH_ANALYTIC_FUNCTION_H