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/* \file
  \brief Defines device-side elementwise operations on TensorView. Note, the operations defined
    in this header are not specialized for any particular data layout and are therefore not
    intended to offer the best possible performance. Rather, they are intended to be generic
    reference implementations to support the HYTLASS unit tests.
*/

#pragma once

// Hytlass includes
#include "hytlass/hytlass.h"
#include "hytlass/tensor_view.h"

#include "hytlass/util/reference/device/tensor_foreach.h"

///////////////////////////////////////////////////////////////////////////////////////////////////

namespace hytlass {
namespace reference {
namespace device {

///////////////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////////////////////

namespace detail {

template <
  typename Element,               ///< Element type
  typename Layout>                ///< Layout function
struct TensorReLuFunc {

  /// View type
  using TensorView = TensorView<Element, Layout>;

  /// Coordinate in tensor's index space
  using TensorCoord = typename TensorView::TensorCoord;

  /// Parameters structure
  struct Params {

    //
    // Data members
    //

    TensorView view;
    Element threshold;


    //
    // Methods
    //

    Params(
      TensorView view_ = TensorView(),
      Element threshold_ = Element(0)
    ):
      view(view_), threshold(threshold_) {

    }
  };

  //
  // Data members
  //

  Params params;

  //
  // Methods
  //

  HYTLASS_DEVICE
  TensorReLuFunc(Params const &params): params(params) {

  }

  HYTLASS_DEVICE
  void operator()(TensorCoord const &coord) {

    Element const & value = params.view.at(coord);
    params.view.at(coord) = (value < params.threshold) ? params.threshold : value;
  }
};

} // namespace detail

///////////////////////////////////////////////////////////////////////////////////////////////////

/// Apply ReLu on a tensor
template <
  typename Element,               ///< Element type
  typename Layout>                ///< Layout function
void TensorReLu(
  TensorView<Element, Layout> view,       ///< destination tensor
  Element threshold = Element(0)) {         ///< ReLu threshold
  
  using Func = detail::TensorReLuFunc<Element, Layout>;
  using Params = typename Func::Params;

  TensorForEach<Func, Layout::kRank, Params>(
    view.extent(),
    Params(view, threshold)
  );
}

///////////////////////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////////////////////

} // namespace device
} // namespace reference
} // namespace hytlass
