/**
 * @file colville_function_impl.hpp
 * @author Marcus Edel
 *
 * Implementation of the Coville 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_COLVILLE_FUNCTION_IMPL_HPP
#define ENSMALLEN_PROBLEMS_COLVILLE_FUNCTION_IMPL_HPP

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

namespace ens {
namespace test {

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

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

template<typename MatType>
typename MatType::elem_type ColvilleFunction::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 x3 = coordinates(2);
  const ElemType x4 = coordinates(3);

  const ElemType objective =
      100 * std::pow(std::pow(x1, ElemType(2)) - x2, ElemType(2)) +
      std::pow(x1 - 1, ElemType(2)) + std::pow(x3 - 1, ElemType(2)) +
      90 * std::pow(std::pow(x3, ElemType(2)) - x4, ElemType(2)) +
      ElemType(10.1) * (std::pow(x2 - 1, ElemType(2)) +
      std::pow(x4 - 1, ElemType(2))) + ElemType(19.8) * (x2 - 1) * (x4 - 1);

  return objective;
}

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

template<typename MatType, typename GradType>
inline void ColvilleFunction::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);
  const ElemType x3 = coordinates(2);
  const ElemType x4 = coordinates(3);

  gradient.set_size(4, 1);
  gradient(0) = 2 * (200 * x1 * (std::pow(x1, ElemType(2)) - x2) + x1 - 1);
  gradient(1) = ElemType(19.8) * x4 - 200 * std::pow(x1, ElemType(2)) +
      ElemType(220.2) * x2 - 40;
  gradient(2) = 2 * (180 * x3 * (std::pow(x3, ElemType(2)) - x4) + x3 - 1);
  gradient(3) = ElemType(200.2) * x4 + ElemType(19.8) * x2 -
      180 * std::pow(x3, ElemType(2)) - 40;
}

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

} // namespace test
} // namespace ens

#endif
