interleaved_epilogue.h

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#pragma once

#include <assert.h>

#include "cutlass/cutlass.h"
#include "cutlass/numeric_types.h"
#include "cutlass/array.h"
#include "cutlass/layout/vector.h"
#include "cutlass/layout/tensor.h"
#include "cutlass/tensor_coord.h"
#include "cutlass/aligned_buffer.h"

#include "cutlass/gemm/gemm.h"

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

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


namespace cutlass {
namespace epilogue {
namespace threadblock {


template <
    typename Shape_,
    typename WarpMmaOperator_,
    int PartitionsK,
    typename OutputTileIterator_,
    typename AccumulatorFragmentIterator_,
    typename OutputOp_,
    int InterleavedK,
    bool IsBetaZero = false>
class InterleavedEpilogue {
 public:
  using Shape = Shape_;
  using WarpMmaOperator = WarpMmaOperator_;
  static int const kPartitionsK = PartitionsK;
  using AccumulatorFragmentIterator = AccumulatorFragmentIterator_;
  using OutputTileIterator = OutputTileIterator_;
  using OutputOp = OutputOp_;

  using Layout = layout::ColumnMajorInterleaved<InterleavedK>;

  using AccumulatorTile = typename AccumulatorFragmentIterator::AccumulatorTile;

  using ElementAccumulator = typename AccumulatorTile::Element;

  using ElementOutput = typename OutputTileIterator::Element;

  static int const kElementsPerAccess = OutputTileIterator::kElementsPerAccess;

  using TensorRef = typename OutputTileIterator::TensorRef;

  using SyncTensorRef =
      typename cutlass::TensorRef<int, cutlass::layout::PackedVectorLayout>;

  using ConstTensorRef = typename OutputTileIterator::ConstTensorRef;

  using OutputAccessType = Array<typename OutputTileIterator::Element,
                                 OutputTileIterator::kElementsPerAccess>;

  using AccumulatorAccessType =
      Array<ElementAccumulator, OutputTileIterator::kElementsPerAccess>;

  using WarpCount =
      gemm::GemmShape<Shape::kM / WarpMmaOperator::Shape::kM,
                      Shape::kN / WarpMmaOperator::Shape::kN, kPartitionsK>;

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

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

  struct SharedStorage {};


 public:
  CUTLASS_DEVICE
  InterleavedEpilogue(
      SharedStorage &shared_storage,  
      int thread_idx,                 
      int warp_idx,                   
      int lane_idx                    
    ) {}

  CUTLASS_DEVICE
  void operator()(
    OutputOp const &output_op,                    
    OutputTileIterator destination_iterator,      
    AccumulatorTile const &accumulators,          
    OutputTileIterator source_iterator) {         

    //
    // Predicated tile iterators constructed from members
    //

    if (IsBetaZero && output_op.is_source_needed())
      assert(0);

    typename OutputTileIterator::Fragment source_fragment;

    if (!IsBetaZero) {
      if (!output_op.is_source_needed()) {
        source_iterator.clear_mask();
      }
    }

    source_fragment.clear();

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

    AccumulatorFragmentIterator accum_fragment_iterator(accumulators);

    //
    // Iterate over accumulator tile
    //

    CUTLASS_PRAGMA_UNROLL
    for (int iter = 0; iter < OutputTileIterator::kIterations; ++iter) {
      //
      // Load the source
      //

      if (!IsBetaZero) {
        source_iterator.set_iteration_index(iter);
        source_iterator.load(source_fragment);
        ++source_iterator;
      }

      //
      // Convert fragment
      //

      typename AccumulatorFragmentIterator::Fragment accum_fragment;

      accum_fragment_iterator.load(accum_fragment);
      ++accum_fragment_iterator;

      //
      // Compute the output result
      //

      typename OutputTileIterator::Fragment output_fragment;
      apply_output_operator_(output_op, output_fragment, accum_fragment, source_fragment);

      //
      // Store the final result
      //

      destination_iterator.set_iteration_index(iter);
      destination_iterator.store(output_fragment);
      ++destination_iterator;
    }
  }

 private:
  CUTLASS_DEVICE
  void apply_output_operator_(
    OutputOp const &output_op,                    
      typename OutputTileIterator::Fragment &output_fragment,
      typename AccumulatorFragmentIterator::Fragment const
          &aligned_accum_fragment,
      typename OutputTileIterator::Fragment const &source_fragment) {
    OutputAccessType *output_frag_ptr =
        reinterpret_cast<OutputAccessType *>(&output_fragment);

    AccumulatorAccessType const *compute_frag_ptr =
        reinterpret_cast<AccumulatorAccessType const *>(
            &aligned_accum_fragment);

    OutputAccessType const *source_frag_ptr =
        reinterpret_cast<OutputAccessType const *>(&source_fragment);

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

    CUTLASS_PRAGMA_UNROLL
    for (int i = 0; i < kOutputOpIterations; ++i) {
      // Call the output operator
      output_frag_ptr[i] = output_op(compute_frag_ptr[i], source_frag_ptr[i]);
    }
  }
};


} // namespace threadblock
} // namespace epilogue
} // namespace cutlass