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/*! \file

  \brief Threadblock-level epilogue computing:
    Aux = ((alpha * scale_a * scale_b) * accumulator) + ((beta * scale_c) * source) + bias
    D = activation(Aux)

    if Aux is fp8 type:
        abs_max_output = max( abs(aux) | (for every aux in Aux))
        Aux = scale_aux * Aux
    endif

    if D is fp8 type:
        abs_max_output = max( abs(d) | (for every d in D))
        D = scale_d * D
    endif

    Parameter Aux is optionally stored to global memory
*/

#pragma once

#include <assert.h>
#include <utility>

#include "hytlass/hytlass.h"
#include "hytlass/array.h"
#include "hytlass/numeric_types.h"
#include "hytlass/numeric_conversion.h"
#include "hytlass/tensor_coord.h"
#include "hytlass/aligned_buffer.h"
#include "hytlass/functional.h"
#include "hytlass/fast_math.h"
#include "hytlass/layout/vector.h"
#include "hytlass/layout/tensor.h"

#include "hytlass/gemm/gemm.h"

#include "hytlass/transform/pitch_linear_thread_map.h"
#include "hytlass/transform/threadblock/regular_tile_iterator.h"

#include "hytlass/epilogue/threadblock/epilogue_base.h"
#include "hytlass/epilogue/threadblock/predicated_tile_iterator.h"

#include "hytlass/numeric_types.h"

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

namespace hytlass {
namespace epilogue {
namespace threadblock {

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

namespace detail {

/// Helper class for keeping track of absolute maximums and performing scaling
template <
  typename Iterator,        // Iterator type used for storing the data for which absolute maximum and scaling
                            // will be computed. This type is used for predicating absolute maximum calculations.
  typename Fragment,        // Type of input to be computed on
  bool ScalingAndAmaxNeeded // Whether to perform absolute maximum and scaling operations
>
struct ScalingAndAmaxHelper;

/// Partial specialization that does not perform scaling or calculate an absolute maximum
template <typename Iterator, typename Fragment>
struct ScalingAndAmaxHelper<Iterator, Fragment, false> {
  using Element = typename Fragment::Element;

  HYTLASS_HOST_DEVICE
  ScalingAndAmaxHelper(Element scale) { }

  HYTLASS_DEVICE
  Fragment operator()(const Iterator& iterator, const Fragment& inp) {
    return inp;
  }

  HYTLASS_HOST_DEVICE
  Element get_abs_max() const {
    return Element(0.);
  }

  HYTLASS_HOST_DEVICE
  void set_scaling_factor(Element scale_) { }
};

/// Partial specialization that keeps track of an absolute maximum value of inputs seen
/// and scales inputs
template <typename Iterator, typename Fragment>
struct ScalingAndAmaxHelper<Iterator, Fragment, true> {
  using Element = typename Fragment::Element;
  using AccessType = typename Iterator::AccessType;
  using ThreadMap = typename Iterator::ThreadMap;

  Element abs_max;
  Element scale;

  // Operators
  maximum_with_nan_propogation<Element> max_op;
  absolute_value_op<Element> abs_op;
  multiplies<Fragment> multiply;

  HYTLASS_HOST_DEVICE
  ScalingAndAmaxHelper(Element scale_) : abs_max(0.), scale(scale_) { }

  // Compute the absolute maximum value between `abs_max` and the entries
  // of `frag` for predicated-on entries of `iterator`. Return a scaled
  // version of `inp`.
  HYTLASS_DEVICE
  Fragment operator()(const Iterator& iterator, const Fragment& frag) {
    using PredicateGroup = Array<Element, Iterator::ThreadMap::kElementsPerAccess>;
    PredicateGroup const *frag_ptr = reinterpret_cast<PredicateGroup const *>(&frag);

    typename Iterator::Mask mask;
    iterator.get_mask(mask);

    HYTLASS_PRAGMA_UNROLL
    for (int cluster = 0; cluster < ThreadMap::Iterations::kCluster; ++cluster) {

      HYTLASS_PRAGMA_UNROLL
      for (int group = 0; group < ThreadMap::Iterations::kGroup; ++group) {

        HYTLASS_PRAGMA_UNROLL
        for (int row = 0; row < ThreadMap::Iterations::kRow; ++row) {
          int frag_row_idx =
            (row + ThreadMap::Iterations::kRow * (group + ThreadMap::Iterations::kGroup * cluster));

          int row_offset = row * ThreadMap::Delta::kRow
            + group * ThreadMap::Delta::kGroup
            + cluster * ThreadMap::Delta::kCluster;

          bool row_guard = ((row_offset + iterator.thread_start_row()) < iterator.extent_row());

          HYTLASS_PRAGMA_UNROLL
          for (int column = 0; column < ThreadMap::Iterations::kColumn; ++column) {
            bool guard = row_guard && mask.predicates[column];

            if (guard) {
              int access_idx = frag_row_idx * ThreadMap::Iterations::kColumn + column;
              HYTLASS_PRAGMA_UNROLL
              for (int i = 0; i < PredicateGroup::kElements; ++i) {
                abs_max = max_op(abs_max, abs_op(frag_ptr[access_idx][i]));
              }
            }
          }
        }
      }
    }

    // Perform scaling
    return multiply(scale, frag);
  }

  HYTLASS_HOST_DEVICE
  Element get_abs_max() const {
    return abs_max;
  }

  HYTLASS_HOST_DEVICE
  void set_scaling_factor(Element scale_) {
    scale = scale_;
  }
};

} // namespace detail

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

template <
  typename Shape_,                          ///< Shape of threadblock tile (concept: GemmShape)
  typename WarpMmaOperator_,                ///< Warp-level MMA operator (concept: gemm::warp::MmaTensorOp)
  int PartitionsK,                          ///< Number of partitions of the K dimension
  typename OutputTileIterator_,             ///< Tile iterator reading and writing output tensors
  typename AuxOutputTileIterator_,          ///< Tile iterator writing auxiliary output tensors
  typename ElementVector_,                  ///< Data type of bias vector
  typename AccumulatorFragmentIterator_,    ///< Fragment iterator selecting accumulators
  typename WarpTileIterator_,               ///< Warp-scoped tile iterator writing accumulators to SMEM
  typename SharedLoadIterator_,             ///< Threadblock-scoped tile iterator loading from SMEM
  typename OutputOp_,                       ///< Output operator
  typename Padding_,                        ///< Padding added to SMEM allocation to avoid bank conflicts (concept: MatrixShape)
  int FragmentsPerPartition = 1,            ///< Used to coarsen the epilogue granularity
  int IterationsUnroll =                    ///< Used to reduce binary size when epilogue op is large
    (!IsEpilogueFunctorHeavy<OutputOp_>::value)
>
class EpilogueWithAbsMax :
  public EpilogueBase<
    Shape_,
    typename WarpMmaOperator_::Shape,
    PartitionsK,
    AccumulatorFragmentIterator_,
    WarpTileIterator_,
    Padding_,
    FragmentsPerPartition> {

public:

  using Base = EpilogueBase<
    Shape_,
    typename WarpMmaOperator_::Shape,
    PartitionsK,
    AccumulatorFragmentIterator_,
    WarpTileIterator_,
    Padding_,
    FragmentsPerPartition>;

  static bool const kIsSingleSource = true;
  using Shape = Shape_;
  using WarpMmaOperator = WarpMmaOperator_;
  static int const kPartitionsK = PartitionsK;
  using OutputTileIterator = OutputTileIterator_;
  using AuxOutputTileIterator = AuxOutputTileIterator_;
  using ElementVector = ElementVector_;
  using AccumulatorFragmentIterator = AccumulatorFragmentIterator_;
  using WarpTileIterator = WarpTileIterator_;
  using SharedLoadIterator = SharedLoadIterator_;
  using OutputOp = OutputOp_;
  using Padding = Padding_;

  using Layout = layout::RowMajor;
  using LongIndex = typename Layout::LongIndex;

  /// The complete warp-level accumulator tile
  using AccumulatorTile = typename Base::AccumulatorTile;

  /// Accumulator element
  using ElementAccumulator = typename WarpTileIterator::Element;

  /// Data type used for absolute maximum value
  using ElementAbsmax = typename OutputOp::ElementAbsmax;

  /// Compute data type produced by the output op
  using ElementCompute = typename OutputOp::ElementCompute;

  /// Compute fragment
  using FragmentCompute = Array<ElementCompute, OutputTileIterator::Fragment::kElements>;

  /// Helpers for (optionally) computing absolute maximums and scaling output and auxiliary output
  using OutputScaler = detail::ScalingAndAmaxHelper<OutputTileIterator,
                                                    FragmentCompute,
                                                    OutputOp::kIsScalingAndAmaxOutputNeeded>;

  using AuxOutputScaler = detail::ScalingAndAmaxHelper<AuxOutputTileIterator,
                                                       FragmentCompute,
                                                       OutputOp::kIsScalingAndAmaxAuxOutputNeeded>;

  /// Thread map used by output tile iterators
  using ThreadMap = typename OutputTileIterator::ThreadMap;

  /// Fragment object used to store the broadcast values
  using BroadcastFragment = Array<
    ElementCompute,
    ThreadMap::Iterations::kColumn * ThreadMap::kElementsPerAccess>;

  /// Output element
  using ElementOutput = typename OutputTileIterator::Element;

  /// Data type of auxiliary output
  using ElementAuxOutput = typename AuxOutputTileIterator::Element;

  /// Output access size
  static int const kElementsPerAccess = OutputTileIterator::kElementsPerAccess;

  /// Tensor reference to destination tensor
  using TensorRef = typename OutputTileIterator::TensorRef;

  /// Tensor reference to sync tensor
  using SyncTensorRef = typename hytlass::TensorRef<int, hytlass::layout::PackedVectorLayout>;

  /// Const tensor reference to source tensor
  using ConstTensorRef = typename OutputTileIterator::ConstTensorRef;

  /// Array type used to output
  using OutputAccessType = Array<
    typename OutputTileIterator::Element, OutputTileIterator::kElementsPerAccess>;

  /// Array type used by output functor
  using AccumulatorAccessType = Array<typename WarpTileIterator::Element, OutputTileIterator::kElementsPerAccess>;

  /// Array type used by output functor
  using ComputeAccessType = Array<ElementCompute, OutputTileIterator::kElementsPerAccess>;

  /// Auxiliary output access type
  using AuxAccessType = Array<ElementAuxOutput, OutputTileIterator::kElementsPerAccess>;

  /// Number of warps
  using WarpCount = typename Base::WarpCount;

  /// Shared memory allocation from epilogue base class
  using BaseSharedStorage = typename Base::SharedStorage;

  static int constexpr kSmemTiles = Base::kFragmentsPerIteration > 1 ? Base::kFragmentsPerIteration : kPartitionsK;
  static int constexpr kSmemPointerOffset = Base::SharedStorage::StorageShape::kCount / kSmemTiles;

  /// Used for the broadcast
  struct BroadcastDetail {

    /// Number of threads per warp
    static int const kWarpSize = WARP_SIZE_GPU;

    static int const kElementsPerAccess = ThreadMap::kElementsPerAccess;

    /// Number of distinct scalar column indices handled by each thread
    static int const kColumnsPerThread = ThreadMap::Iterations::kColumn * ThreadMap::kElementsPerAccess;

    /// Number of distinct scalar row indices handled by each thread
    static int const kRowsPerThread = ThreadMap::Iterations::kCount / ThreadMap::Iterations::kColumn;

    /// Number of threads per threadblock
    static int const kThreadCount = kWarpSize * WarpCount::kCount;

    /// Number of distinct threads per row of output tile
    static int const kThreadsPerRow = (Shape::kN / kColumnsPerThread);

    /// Number of distinct threads which must be reduced during the final reduction phase within the threadblock.
    static int const kThreadRows = kThreadCount / kThreadsPerRow;

    /// I'm not sure what I meant here.
    static int const kThreadAccessesPerRow = const_max(1, (Shape::kN + kThreadCount - 1) / kThreadCount);

    /// Shape of the shared memory allocation for the epilogue
    using StorageShape = MatrixShape<
      kThreadRows,
      Shape::kN
    >;

    /// Debug printing
    HYTLASS_DEVICE
    static void print() {
#if 0
      printf("BroadcastDetail {\n");
      printf(
        "  kColumnsPerThread: %d\nkRowsPerThread: %d\n,kThreadCount: %d\nkThreadsPerRow: %d\n"
        "kThreadRows: %d\nThreadAccessesPerRow: %d\nStorageShape: %d x %d (count: %d)\n",
        kColumnsPerThread,
        kRowsPerThread,
        kThreadCount,
        kThreadsPerRow,
        kThreadRows,
        kThreadAccessesPerRow,
        StorageShape::kRow,
        StorageShape::kColumn,
        StorageShape::kCount
      );
      printf("};\n");
#endif
    }
  };

  /// Shared storage structure (shadows base) with additional SMEM buffer for reduction
  struct SharedStorage {
    union {
      BaseSharedStorage base;
    };

    HYTLASS_HOST_DEVICE
    SharedStorage() { }
  };

public:


  static_assert(SharedLoadIterator::Fragment::kElements == OutputTileIterator::Fragment::kElements,
    "Mismatch between shared load iterator and output tile iterator.");

  static_assert(OutputTileIterator::kElementsPerAccess, "OutputTileIterator::kElementsPerAccess must not be zero.");

  static_assert(!(OutputTileIterator::Fragment::kElements % OutputTileIterator::kElementsPerAccess),
    "Divisibility");

private:

  /// Loads fragment from shared memory aligned with output tensor
  SharedLoadIterator shared_load_iterator_;

  /// Thread index within the threadblock
  int thread_idx_;

public:

  /// Constructor
  HYTLASS_DEVICE
  EpilogueWithAbsMax(
    SharedStorage &shared_storage,                    ///< Shared storage object
    int thread_idx,                                   ///< ID of a thread within the threadblock
    int warp_idx,                                     ///< ID of warp within threadblock
    int lane_idx                                      ///< Id of thread within warp
  ):
    Base(shared_storage.base, thread_idx, warp_idx, lane_idx),
    shared_load_iterator_(shared_storage.base.reference(), thread_idx),
    thread_idx_(thread_idx)
  {

  }

  /// Streams the result to global memory
  HYTLASS_DEVICE
  void operator()(
    OutputOp &output_op,                              ///< Output operator
    ElementVector const * broadcast_ptr,              ///< Broadcast vector
    OutputTileIterator destination_iterator,          ///< Tile iterator for destination
    AccumulatorTile const &accumulators,              ///< Complete warp-level accumulator tile
    OutputTileIterator source_iterator,               ///< Tile iterator for source accumulator matrix
    AuxOutputTileIterator aux_iterator,               ///< Tile iterator for destination auxiliary output
    MatrixCoord const &problem_size =                 ///< Problem size needed to guard against out-of-bounds accesses
        MatrixCoord(Shape::kM, Shape::kN),
    MatrixCoord const &threadblock_offset =           ///< Threadblock's initial offset within the problem size space
        MatrixCoord()) {

    BroadcastFragment broadcast_fragment;

    load_broadcast_fragment_(broadcast_fragment, broadcast_ptr, problem_size, threadblock_offset);

    OutputScaler output_scaler(output_op.get_scale_d());

    AuxOutputScaler aux_scaler(output_op.get_scale_aux());

    if (!output_op.is_source_needed()) {
      compute_source_not_needed_(
        output_op,
        broadcast_fragment,
        destination_iterator,
        accumulators,
        aux_iterator,
        output_scaler,
        aux_scaler);
    }
    else {
      compute_source_needed_(
        output_op,
        broadcast_fragment,
        destination_iterator,
        accumulators,
        source_iterator,
        aux_iterator,
        output_scaler,
        aux_scaler);
    }

    // Store the absolute maximum values of the output and auxiliar tensors, if needed.
    if (output_op.get_ptr_output_abs_max() != nullptr) {
      ElementAbsmax local_abs_max =
          NumericConverter<ElementAbsmax, ElementCompute, OutputOp::kRound>{}(output_scaler.get_abs_max());
      atomic_maximum<ElementAbsmax>{}(
        output_op.get_ptr_output_abs_max(), local_abs_max);
    }

    if (output_op.get_ptr_aux_output_abs_max() != nullptr) {
      ElementAbsmax local_abs_max =
          NumericConverter<ElementAbsmax, ElementCompute, OutputOp::kRound>{}(aux_scaler.get_abs_max());
      atomic_maximum<ElementAbsmax>{}(
        output_op.get_ptr_aux_output_abs_max(), local_abs_max);
    }
  }

private:

  HYTLASS_DEVICE
  void load_broadcast_fragment_(
    BroadcastFragment & broadcast_fragment,      ///< Fragment containing the accumulated partial reduction over columns
    ElementVector const * broadcast_ptr,         ///< Broadcast vector
    MatrixCoord const &problem_size,             ///< Problem size needed to guard against out-of-bounds accesses
    MatrixCoord const &threadblock_offset        ///< Threadblock's initial offset within the problem size space
    ) {

    broadcast_fragment.clear();

    // If no pointer is supplied, set with all zeros and avoid memory accesses
    if (!broadcast_ptr) {
      return;
    }

    int thread_initial_column = ThreadMap::initial_offset(thread_idx_).column();

    int thread_column_idx = threadblock_offset.column() + thread_initial_column;
    broadcast_ptr += thread_initial_column;

    NumericArrayConverter<ElementCompute, ElementVector, BroadcastDetail::kElementsPerAccess> converter;
    using AccessType = AlignedArray<ElementVector, BroadcastDetail::kElementsPerAccess>;
    using ComputeFragmentType = Array<ElementCompute, BroadcastDetail::kElementsPerAccess>;

    ComputeFragmentType *frag_ptr = reinterpret_cast<ComputeFragmentType *>(&broadcast_fragment);

    HYTLASS_PRAGMA_UNROLL
    for (int j = 0; j < ThreadMap::Iterations::kColumn; ++j) {

      AccessType loaded;

      loaded.clear();

      if (thread_column_idx < problem_size.column()) {
        loaded = *reinterpret_cast<AccessType const *>(broadcast_ptr);
      }

      ComputeFragmentType cvt = converter(loaded);
      frag_ptr[j] = cvt;

      thread_column_idx += ThreadMap::Delta::kColumn;
      broadcast_ptr += ThreadMap::Delta::kColumn;
    }
  }

  template <class Seq>
  struct acc2smem_source_not_needed;

  template <size_t... Seq>
  struct acc2smem_source_not_needed<hytlass::index_sequence<Seq...>> {
    template <int Advance>
    HYTLASS_DEVICE static void helper(AccumulatorFragmentIterator accum_fragment_iterator,
                                      WarpTileIterator &warp_tile_iterator) {
      HYTLASS_PRAGMA_UNROLL
      for (int i = 0; i < Advance; i++) {
        ++accum_fragment_iterator;
      }

      HYTLASS_PRAGMA_UNROLL
      for (int p = 0; p < Base::kFragmentsPerIteration; ++p) {
        typename AccumulatorFragmentIterator::Fragment accum_fragment;

        accum_fragment_iterator.load(accum_fragment);
        ++accum_fragment_iterator;

        warp_tile_iterator.store(accum_fragment);
        if (p < Base::kFragmentsPerIteration - 1) {
          warp_tile_iterator.add_pointer_offset(kSmemPointerOffset);
        }
      }

      if (Base::kFragmentsPerIteration > 1) {
        warp_tile_iterator.add_pointer_offset(kSmemPointerOffset *
                                              (1 - Base::kFragmentsPerIteration));
      }
    }

    HYTLASS_DEVICE
    static void push(size_t pos,
                     AccumulatorFragmentIterator const &iterator_begin,
                     WarpTileIterator &warp_tile_iterator) {
      int dummy[] = {
          (pos == (Seq * Base::kFragmentsPerIteration)) &&
          (helper<Seq * Base::kFragmentsPerIteration>(iterator_begin, warp_tile_iterator), 0)...};

      HYTLASS_UNUSED(dummy[0]);
    }
  };

  /// Streams the result to global memory
  HYTLASS_DEVICE
  void compute_source_not_needed_(
    OutputOp &output_op,                              ///< Output operator
    BroadcastFragment const &broadcast_fragment,      ///< Fragment containing the accumulated partial reduction over columns
    OutputTileIterator destination_iterator,          ///< Tile iterator for destination
    AccumulatorTile const &accumulators,              ///< Complete warp-level accumulator tile
    AuxOutputTileIterator aux_iterator,               ///< Tile iterator for destination auxiliary output
    OutputScaler& output_scaler,                      ///< Helper for (optionally) computing the absolute maximum and scaling output
    AuxOutputScaler& aux_scaler                       ///< Helper for (optionally) computing the absolute maximum and scaling the auxiliary output
    ) {

    //
    // Iterator over warp-level accumulator fragment
    //

    AccumulatorFragmentIterator accum_fragment_iterator(accumulators);

    //
    // Iterate over accumulator tile
    //

    // HYTLASS_PRAGMA_UNROLL
    #pragma unroll
    for (int iter = 0; iter < OutputTileIterator::kIterations; iter += Base::kFragmentsPerIteration) {

      //
      // Convert and store fragment
      //


      __syncthreads();

      acc2smem_source_not_needed<
          hytlass::make_index_sequence<OutputTileIterator::kIterations /
                                   Base::kFragmentsPerIteration>>::push(iter,
                                                                        accum_fragment_iterator,
                                                                        this->warp_tile_iterator_);

      __syncthreads();

      //
      // Load fragments from shared memory
      //

      HYTLASS_PRAGMA_UNROLL
      for (int p = 0; p < Base::kFragmentsPerIteration; ++p) {


        typename SharedLoadIterator::Fragment aligned_accum_fragment[kPartitionsK];

        shared_load_iterator_.load(aligned_accum_fragment[0]);

        if (p < Base::kFragmentsPerIteration - 1) {
          shared_load_iterator_.add_pointer_offset(kSmemPointerOffset);
        }
        else if (kPartitionsK > 1) {

          plus <typename SharedLoadIterator::Fragment> add_fragments;

          HYTLASS_PRAGMA_UNROLL
          for ( int i = 1; i < kPartitionsK; ++i) {
            shared_load_iterator_.add_pointer_offset(kSmemPointerOffset);
            shared_load_iterator_.load(aligned_accum_fragment[i]);
            aligned_accum_fragment[0] = add_fragments(aligned_accum_fragment[0], aligned_accum_fragment[i]);
          }

          shared_load_iterator_.add_pointer_offset((1 - kPartitionsK) * kSmemPointerOffset);
        }

        //
        // Apply output operation
        //

        FragmentCompute frag_Z_compute;
        FragmentCompute frag_Aux_compute;

        apply_output_operator_source_not_needed_(
          frag_Z_compute,
          frag_Aux_compute,
          output_op,
          aligned_accum_fragment[0],
          broadcast_fragment);

        //
        // Conditionally store fragments
        //

        // (Optionally) compute the absolute maximum of frag_Z and scale frag_Z
        frag_Z_compute = output_scaler(destination_iterator, frag_Z_compute);
        NumericArrayConverter<typename OutputTileIterator::Fragment::Element, ElementCompute,
                              OutputTileIterator::Fragment::kElements> cvt_to_dst;
        typename OutputTileIterator::Fragment frag_Z = cvt_to_dst(frag_Z_compute);

        // Always store the output
        destination_iterator.store(frag_Z);
        ++destination_iterator;

        // Only store the auxiliary output if scaling and absolute-maximum calculation were needed
        if (OutputOp::kIsScalingAndAmaxAuxOutputNeeded) {
          frag_Aux_compute = aux_scaler(aux_iterator, frag_Aux_compute);

          NumericArrayConverter<typename AuxOutputTileIterator::Fragment::Element, ElementCompute,
                                AuxOutputTileIterator::Fragment::kElements> cvt_to_aux;
          typename AuxOutputTileIterator::Fragment frag_Aux = cvt_to_aux(frag_Aux_compute);
          aux_iterator.store(frag_Aux);
          ++aux_iterator;
        }
      }

      if (Base::kFragmentsPerIteration > 1) {
        shared_load_iterator_.add_pointer_offset(kSmemPointerOffset * (1 - Base::kFragmentsPerIteration));
      }
    }
  }


  template<class Seq>
  struct acc2smem_source_needed;

  template <size_t... Seq>
  struct acc2smem_source_needed<hytlass::index_sequence<Seq...>> {
    template<int Advance>
    HYTLASS_DEVICE
    static void helper(AccumulatorFragmentIterator accum_fragment_iterator,
                       WarpTileIterator &warp_tile_iterator) {
      HYTLASS_PRAGMA_UNROLL
      for (int i = 0; i < Advance; i++) {
        ++accum_fragment_iterator;
      }

      typename AccumulatorFragmentIterator::Fragment accum_fragment;
      accum_fragment_iterator.load(accum_fragment);
      warp_tile_iterator.store(accum_fragment);
    }

    HYTLASS_DEVICE
    static void push(size_t pos,
                     AccumulatorFragmentIterator const &iterator_begin,
                     WarpTileIterator &warp_tile_iterator) {
      int dummy[] = {(pos == Seq) && (helper<Seq>(iterator_begin, warp_tile_iterator), 0)...};
    }
  };


  /// Streams the result to global memory
  HYTLASS_DEVICE
  void compute_source_needed_(
    OutputOp &output_op,                          ///< Output operator
    BroadcastFragment const &broadcast_fragment,  ///< Fragment containing the accumulated partial reduction over columns
    OutputTileIterator destination_iterator,      ///< Tile iterator for destination
    AccumulatorTile const &accumulators,          ///< Complete warp-level accumulator tile
    OutputTileIterator source_iterator,           ///< Tile iterator for source accumulator matrix
    AuxOutputTileIterator aux_iterator,               ///< Tile iterator for destination auxiliary output
    OutputScaler& output_scaler,                      ///< Helper for (optionally) computing the absolute maximum and scaling output
    AuxOutputScaler& aux_scaler                       ///< Helper for (optionally) computing the absolute maximum and scaling the auxiliary output
    ) {

    typename OutputTileIterator::Fragment source_fragment;
    source_fragment.clear();

    //
    // Iterator over warp-level accumulator fragment
    //

    AccumulatorFragmentIterator accum_fragment_iterator(accumulators);

    //
    // Iterate over accumulator tile
    //

    #pragma unroll
    for (int iter = 0; iter < OutputTileIterator::kIterations; ++iter) {

      //
      // Load the source
      //

      source_iterator.load(source_fragment);
      ++source_iterator;

      //
      // Convert and store fragment
      //

      __syncthreads();

      acc2smem_source_needed<hytlass::make_index_sequence<OutputTileIterator::kIterations>>::push(
          iter, accum_fragment_iterator, this->warp_tile_iterator_);

      __syncthreads();

      //
      // Load fragments from shared memory
      //

      typename SharedLoadIterator::Fragment aligned_accum_fragment[kPartitionsK];

      shared_load_iterator_.load(aligned_accum_fragment[0]);

      // If the number of k-slices is > 1 - perform a reduction amongst the k-slices
      if (kPartitionsK > 1)
      {
        plus <typename SharedLoadIterator::Fragment> add_fragments;
        const int tile_row_offset = Base::SharedStorage::StorageShape::kRow / PartitionsK;

        HYTLASS_PRAGMA_UNROLL
        for ( int i = 1; i < kPartitionsK; ++i) {
          shared_load_iterator_.add_tile_offset({tile_row_offset , 0});
          shared_load_iterator_.load(aligned_accum_fragment[i]);
          aligned_accum_fragment[0] = add_fragments(aligned_accum_fragment[0], aligned_accum_fragment[i]);
        }

        shared_load_iterator_.add_tile_offset({-1 * (kPartitionsK-1) * tile_row_offset, 0});
      }

      //
      // Apply output operation
      //

      FragmentCompute frag_Z_compute;
      FragmentCompute frag_Aux_compute;

      apply_output_operator_(
        frag_Z_compute,
        frag_Aux_compute,
        output_op,
        aligned_accum_fragment[0],
        source_fragment,
        broadcast_fragment);

      //
      // Conditionally store fragments
      //

      // (Optionally) compute the absolute maximum of frag_Z and scale frag_Z
      frag_Z_compute = output_scaler(destination_iterator, frag_Z_compute);
      NumericArrayConverter<typename OutputTileIterator::Fragment::Element, ElementCompute,
                            OutputTileIterator::Fragment::kElements> cvt_to_dst;
      typename OutputTileIterator::Fragment frag_Z = cvt_to_dst(frag_Z_compute);

      // Always store the output
      destination_iterator.store(frag_Z);
      ++destination_iterator;

      // Only store the auxiliary output if scaling and absolute-maximum calculation were needed
      if (OutputOp::kIsScalingAndAmaxAuxOutputNeeded) {
        frag_Aux_compute = aux_scaler(aux_iterator, frag_Aux_compute);

        NumericArrayConverter<typename AuxOutputTileIterator::Fragment::Element, ElementCompute,
                              AuxOutputTileIterator::Fragment::kElements> cvt_to_aux;
        typename AuxOutputTileIterator::Fragment frag_Aux = cvt_to_aux(frag_Aux_compute);
        aux_iterator.store(frag_Aux);
        ++aux_iterator;
      }
    }
  }

  /// Helper to invoke the output functor over each vector of output
  HYTLASS_DEVICE
  void apply_output_operator_(
    FragmentCompute &frag_Z,
    FragmentCompute &frag_Aux,
    OutputOp &output_op,
    typename SharedLoadIterator::Fragment const &frag_AB,
    typename OutputTileIterator::Fragment const &frag_C,
    BroadcastFragment const &frag_Broadcast) {

    using AccessTypeZ = Array<ElementCompute, kElementsPerAccess>;
    using AccessTypeAux = Array<ElementCompute, kElementsPerAccess>;
    using AccessTypeBroadcast = Array<ElementCompute, kElementsPerAccess>;

    AccessTypeZ *frag_Z_ptr = reinterpret_cast<AccessTypeZ *>(&frag_Z);
    AccessTypeAux *frag_Aux_ptr = reinterpret_cast<AccessTypeAux *>(&frag_Aux);

    AccumulatorAccessType const *frag_AB_ptr =
      reinterpret_cast<AccumulatorAccessType const *>(&frag_AB);

    OutputAccessType const *frag_C_ptr =
      reinterpret_cast<OutputAccessType const *>(&frag_C);

    AccessTypeBroadcast const *frag_Broadcast_ptr =
      reinterpret_cast<AccessTypeBroadcast const *>(&frag_Broadcast);

    int const kOutputOpIterations =
      OutputTileIterator::Fragment::kElements / OutputTileIterator::kElementsPerAccess;

    HYTLASS_PRAGMA_UNROLL
    for (int i = 0; i < kOutputOpIterations; ++i) {
        output_op(
          frag_Z_ptr[i],
          frag_Aux_ptr[i],
          frag_AB_ptr[i],
          frag_Broadcast_ptr[i % ThreadMap::Iterations::kColumn],
          frag_C_ptr[i]);
    }
  }

  /// Helper to invoke the output functor over each vector of output
  HYTLASS_DEVICE
  void apply_output_operator_source_not_needed_(
    FragmentCompute &frag_Z,
    FragmentCompute &frag_Aux,
    OutputOp &output_op,
    typename SharedLoadIterator::Fragment const &frag_AB,
    BroadcastFragment const &frag_Broadcast) {

    using AccessTypeZ = Array<ElementCompute, kElementsPerAccess>;
    using AccessTypeAux = Array<ElementCompute, kElementsPerAccess>;
    using AccessTypeBroadcast = Array<ElementCompute, kElementsPerAccess>;

    AccessTypeZ *frag_Z_ptr = reinterpret_cast<AccessTypeZ *>(&frag_Z);
    AccessTypeAux *frag_Aux_ptr = reinterpret_cast<AccessTypeAux *>(&frag_Aux);

    AccumulatorAccessType const *frag_AB_ptr =
      reinterpret_cast<AccumulatorAccessType const *>(&frag_AB);

    AccessTypeBroadcast const *frag_Broadcast_ptr =
      reinterpret_cast<AccessTypeBroadcast const *>(&frag_Broadcast);

    int const kOutputOpIterations =
      OutputTileIterator::Fragment::kElements / OutputTileIterator::kElementsPerAccess;

    HYTLASS_PRAGMA_UNROLL
    for (int i = 0; i < kOutputOpIterations; ++i) {

      output_op(
        frag_Z_ptr[i],
        frag_Aux_ptr[i],
        frag_AB_ptr[i],
        frag_Broadcast_ptr[i % ThreadMap::Iterations::kColumn]);
    }
  }
};

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

} // namespace threadblock
} // namespace epilogue
} // namespace hytlass

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