/**
 * @file three_hump_camel_function_impl.hpp
 * @author Suryoday Basak
 *
 * Implementation of the Three-hump camel function.
 *
 * ensmallen is free software; you may redistribute it and/or modify it under
 * the terms of the 3-clause BSD license.  You should have received a copy of
 * the 3-clause BSD license along with ensmallen.  If not, see
 * http://www.opensource.org/licenses/BSD-3-Clause for more information.
 */
#ifndef ENSMALLEN_PROBLEMS_THREE_HUMP_CAMEL_FUNCTION_IMPL_HPP
#define ENSMALLEN_PROBLEMS_THREE_HUMP_CAMEL_FUNCTION_IMPL_HPP

// In case it hasn't been included yet.
#include "three_hump_camel_function.hpp"

namespace ens {
namespace test {

inline ThreeHumpCamelFunction::ThreeHumpCamelFunction()
{ /* Nothing to do here */ }

inline void ThreeHumpCamelFunction::Shuffle() { /* Nothing to do here */ }

template<typename MatType>
typename MatType::elem_type ThreeHumpCamelFunction::Evaluate(
    const MatType& coordinates,
    const size_t /* begin */,
    const size_t /* batchSize */) const
{
  // Convenience typedef.
  typedef typename MatType::elem_type ElemType;

  // For convenience; we assume these temporaries will be optimized out.
  const ElemType x1 = coordinates(0);
  const ElemType x2 = coordinates(1);

  const ElemType objective = (2 * std::pow(x1, ElemType(2))) -
      (ElemType(1.05) * std::pow(x1, ElemType(4))) +
      (std::pow(x1, ElemType(6)) / 6) + (x1 * x2) + std::pow(x2, ElemType(2));
  return objective;
}

template<typename MatType>
typename MatType::elem_type ThreeHumpCamelFunction::Evaluate(
    const MatType& coordinates) const
{
  return Evaluate(coordinates, 0, NumFunctions());
}

template<typename MatType, typename GradType>
inline void ThreeHumpCamelFunction::Gradient(const MatType& coordinates,
                                             const size_t /* begin */,
                                             GradType& gradient,
                                             const size_t /* batchSize */) const
{
  // Convenience typedef.
  typedef typename MatType::elem_type ElemType;

  // For convenience; we assume these temporaries will be optimized out.
  const ElemType x1 = coordinates(0);
  const ElemType x2 = coordinates(1);

  gradient.set_size(2, 1);
  gradient(0) = std::pow(x1, ElemType(5)) -
      (ElemType(4.2) * std::pow(x1, ElemType(3))) + (4 * x1) + x2;
  gradient(1) = x1 + (2 * x2);
}

template<typename MatType, typename GradType>
inline void ThreeHumpCamelFunction::Gradient(const MatType& coordinates,
                                             GradType& gradient)
{
  Gradient(coordinates, 0, gradient, 1);
}

} // namespace test
} // namespace ens

#endif
