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/*! \file
  \brief Functor performing conversion operations used by epilogues.
*/

#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/numeric_types.h"
#include "cutlass/array.h"
#include "cutlass/functional.h"
#include "cutlass/numeric_conversion.h"

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

namespace cutlass {
namespace epilogue {
namespace thread {

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

/// Converts the result without other operations
///
template <
  typename ElementOutput_,                             ///< Data type used to load and store tensors
  int Count,                                           ///< Number of elements computed per operation
  typename ElementAccumulator_ = ElementOutput_,       ///< Accumulator data type
  FloatRoundStyle Round = FloatRoundStyle::round_to_nearest
>
class Convert {
public:

  using ElementOutput = ElementOutput_;
  using ElementAccumulator = ElementAccumulator_;
  using ElementCompute = ElementAccumulator_;
  using ElementD = ElementOutput;                     // for use with cute::collective::DefaultEpilogue

  static int const kCount = Count;

  using FragmentOutput = Array<ElementOutput, kCount>;
  using FragmentAccumulator = Array<ElementAccumulator, kCount>;
  using ComputeFragment = FragmentAccumulator;

  static FloatRoundStyle const kRound = Round;

  static bool const kIsHeavy = false;

  /// Host-constructable parameters structure
  struct Params {

    //
    // Methods
    //

    CUTLASS_HOST_DEVICE
    Params() {}
  };

public:

  /// Constructs the function object, possibly loading from pointers in host memory
  CUTLASS_HOST_DEVICE
  Convert(Params const &params = Params()) {

  }

  /// Functionally required for serial reduction in the epilogue
  CUTLASS_HOST_DEVICE
  void set_k_partition(int k_partition, int k_partition_count) {

  }

  /// Returns true if source is needed based on state of runtime arguments
  CUTLASS_HOST_DEVICE
  constexpr bool is_source_needed() const {
    return false;
  }

  /// Constexpr function to enable the compiler to optimize away the source loading if it is
  /// never needed.
  CUTLASS_HOST_DEVICE
  constexpr bool is_source_ever_needed() const {
    return false;
  }

  /// Computes linear scaling: D = alpha * accumulator + beta * source
  CUTLASS_HOST_DEVICE
  FragmentOutput operator()(
    FragmentAccumulator const &accumulator, 
    FragmentOutput const &source = FragmentOutput(),
    ElementCompute uniform = ElementCompute(0)) const {

    // Convert to destination numeric type
    NumericArrayConverter<ElementOutput, ElementAccumulator, kCount, Round> destination_converter;

    return destination_converter(accumulator);
  }

  //
  // Specializations for scalar (for use with cute::collective::DefaultEpilogue)
  //
  CUTLASS_HOST_DEVICE
  ElementD operator()(ElementAccumulator const accumulator, ElementAccumulator const source) const {
    NumericConverter<ElementD, ElementAccumulator, Round> destination_converter;
    return destination_converter(source);
  }

  CUTLASS_HOST_DEVICE
  ElementD operator()(ElementAccumulator const accumulator) const {
    NumericConverter<ElementD, ElementAccumulator, Round> destination_converter;
    return destination_converter(accumulator);
  }
};

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

} // namespace thread
} // namespace epilogue
} // namespace cutlass