cutlass/include/cutlass/transform/threadblock/vector_iterator.h

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/*! \file
    \brief Template wraps the vector access iterator concept to load whole vector from tensors in
      memory. This is typically used for per-channel scale and bias in convolution kernels.
*/

#pragma once

#include "cutlass/transform/threadblock/predicated_vector_access_iterator.h"

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

namespace cutlass {
namespace transform {
namespace threadblock {

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

template <typename VectorAccessIterator_>
class VectorIterator {
public:
  using VectorAccessIterator = VectorAccessIterator_;

  using Shape = typename VectorAccessIterator::Shape;
  using Element = typename VectorAccessIterator::Element;
  using Layout = typename VectorAccessIterator::Layout;
  using TensorCoord = typename Layout::TensorCoord;
  using AccessType = typename VectorAccessIterator::AccessType;
  using TensorRef = typename VectorAccessIterator::TensorRef;
  using Index = typename VectorAccessIterator::Index;
  using LongIndex = typename VectorAccessIterator::LongIndex;

  static int const kElementsPerAccess = VectorAccessIterator::kElementsPerAccess;
  static int const kRowsPerIteration = VectorAccessIterator::kRowsPerIteration;
  static int const kThreads = VectorAccessIterator::kThreads;
  static int const kIterations = VectorAccessIterator::kIterations;

  /// Fragment object to be loaded or stored
  using Fragment = cutlass::Array<
    Element, kElementsPerAccess * kIterations>;

private:

  /// Internal state
  VectorAccessIterator vector_access_iterator_;

public:

  /// Constructor
  CUTLASS_HOST_DEVICE
  VectorIterator(
    Element const *ptr,
    TensorCoord extent,
    int thread_idx,
    int warp_idx,
    MatrixCoord const &threadblock_offset = MatrixCoord()
  ):
    vector_access_iterator_(ptr, extent, thread_idx, warp_idx, threadblock_offset) { }

  /// Advances to the next tile in memory.
  CUTLASS_HOST_DEVICE
  VectorIterator &operator++() {
    vector_access_iterator_.advance();
    return *this;
  }

  /// Advances to the next tile in memory.
  CUTLASS_HOST_DEVICE
  VectorIterator operator++(int) {
    VectorIterator self(*this);
    operator++();
    return self;
  }

  /// Loads a fragment from memory
  CUTLASS_DEVICE
  void load_with_pointer_offset(Fragment &frag, Index pointer_offset) {

    frag.clear();
    AccessType *frag_ptr = reinterpret_cast<AccessType *>(&frag);

    CUTLASS_PRAGMA_UNROLL
      for (int c = 0; c < kIterations; ++c) {

        cutlass::arch::global_load<
          AccessType,
          sizeof(AccessType)
        >(
          frag_ptr[c],
          vector_access_iterator_.get() + pointer_offset,
          vector_access_iterator_.valid()
        );

        ++vector_access_iterator_;
      }
//    }
  }

  /// Loads a fragment from memory
  CUTLASS_DEVICE
  void load(Fragment &frag) {
    vector_access_iterator_.set_iteration_index(0);
    load_with_pointer_offset(frag, 0);
  }

  CUTLASS_DEVICE
  void advance() {
    vector_access_iterator_.advance();
  }

};

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

} // namespace threadblock
} // namespace transform
} // namespace cutlass

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