/*
 *  This file is a part of TiledArray.
 *  Copyright (C) 2014  Virginia Tech
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  Justus Calvin
 *  Department of Chemistry, Virginia Tech
 *
 *  unary_reduction.h
 *  Apr 2, 2014
 *
 */

#ifndef TILEDARRAY_TILE_OP_UNARY_REDUCTION_H__INCLUDED
#define TILEDARRAY_TILE_OP_UNARY_REDUCTION_H__INCLUDED

#include <TiledArray/tile_op/tile_interface.h>

namespace TiledArray {

/// Tile sum reduction

/// This reduction operation is used to sum all elements of a tile.
/// \tparam Tile The tile type
template <typename Tile>
class SumReduction {
 public:
  // typedefs
  using result_type = decltype(sum(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const { return result_type(0); }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result += arg;
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::sum;
    result += sum(arg);
  }
};  // class SumReduction

/// Tile product reduction

/// This reduction operation is used to multiply all elements of a tile.
/// \tparam Tile The tile type
template <typename Tile>
class ProductReduction {
 public:
  // typedefs
  using result_type = decltype(product(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const { return result_type(1); }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result *= arg;
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::product;
    result *= product(arg);
  }

};  // class ProductReduction

/// Tile trace reduction

/// This reduction operation is used to sum the hyper-diagonal elements of a
/// tile.
/// \tparam Tile The tile type
template <typename Tile>
class TraceReduction {
 public:
  // typedefs
  using result_type = decltype(trace(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const { return result_type(0); }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result += arg;
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::trace;
    result += trace(arg);
  }

};  // class TraceReduction

/// Squared norm tile reduction

/// This reduction operation is used to sum the square of all elements of a
/// tile.
/// \tparam Tile The tile type
template <typename Tile>
class SquaredNormReduction {
 public:
  // typedefs
  using result_type = decltype(squared_norm(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const { return result_type(0); }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result += arg;
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::squared_norm;
    result += squared_norm(arg);
  }

};  // class SquaredNormReduction

/// Minimum tile reduction

/// This reduction operation is used to find the minimum value of elements in a
/// Tile. \tparam Tile The tile type \note the implementation is only enabled if
/// is_strictly_ordered<Tile::numeric_type>::value is true
template <typename Tile, typename Enabler = void>
class MinReduction;

template <typename Tile>
class MinReduction<Tile, typename std::enable_if<detail::is_strictly_ordered<
                             detail::numeric_t<Tile>>::value>::type> {
 public:
  // typedefs
  using result_type = decltype(min(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const {
    return std::numeric_limits<result_type>::max();
  }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result = std::min(result, arg);
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::min;
    result = std::min(result, min(arg));
  }

};  // class MinReduction

/// Maximum tile reduction

/// This reduction operation is used to find the maximum value of elements in a
/// Tile. \tparam Tile The tile type \note the implementation is only enabled if
/// is_strictly_ordered<Tile::numeric_type>::value is true
template <typename Tile, typename Enabler = void>
class MaxReduction;

template <typename Tile>
class MaxReduction<Tile, typename std::enable_if<detail::is_strictly_ordered<
                             detail::numeric_t<Tile>>::value>::type> {
 public:
  // typedefs
  using result_type = decltype(max(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const {
    return std::numeric_limits<result_type>::min();
  }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result = std::max(result, arg);
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::max;
    result = std::max(result, max(arg));
  }

};  // class MaxReduction

/// Minabs tile reduction

/// This reduction operation is used to find the minimum absolute value of
/// elements in a Tile. tiles. \tparam Tile The tile type
template <typename Tile>
class AbsMinReduction {
 public:
  // typedefs
  using result_type = decltype(abs_min(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const {
    return std::numeric_limits<result_type>::max();
  }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result = std::min(result, std::abs(arg));
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::abs_min;
    result = std::min(result, abs_min(arg));
  }

};  // class AbsMinReduction

/// Maxabs tile reduction

/// This reduction operation is used to find the maximum absolute value of
/// element in a Tile. \tparam Tile The tile type
template <typename Tile>
class AbsMaxReduction {
 public:
  // typedefs
  using result_type = decltype(abs_max(std::declval<Tile>()));
  typedef Tile argument_type;

  // Reduction functions

  // Make an empty result object
  result_type operator()() const { return result_type(0); }

  // Post process the result
  const result_type& operator()(const result_type& result) const {
    return result;
  }

  // Reduce two result objects
  void operator()(result_type& result, const result_type& arg) const {
    result = std::max(result, std::abs(arg));
  }

  // Reduce an argument
  void operator()(result_type& result, const argument_type& arg) const {
    using TiledArray::abs_max;
    result = std::max(result, abs_max(arg));
  }

};  // class AbsMaxReduction

}  // namespace TiledArray

#endif  // TILEDARRAY_TILE_OP_UNARY_REDUCTION_H__INCLUDED
