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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 CUTLASS unit tests.
*/

#pragma once

// Cutlass includes
#include "cutlass/cutlass.h"
#include "cutlass/tensor_view.h"

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

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

namespace cutlass {
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
    //

    CUTLASS_DEVICE
    TensorReLuFunc(Params const& params) : params(params) {}

    CUTLASS_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 cutlass
