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/*! \file
    \brief Templates implementing loading of convolution tiles mapped to GEMM A (activation tile)
    matrix from memory.

    This iterator assumes TensorNHWC layout of tensors in Global Memory.
*/

#pragma once

#include "hytlass/array.h"
#include "hytlass/conv/conv2d_problem_size.h"
#include "hytlass/conv/convolution.h"
#include "hytlass/conv/threadblock/depthwise_direct_conv_params.h"
#include "hytlass/coord.h"
#include "hytlass/hytlass.h"
#include "hytlass/layout/matrix.h"
#include "hytlass/layout/pitch_linear.h"
#include "hytlass/layout/tensor.h"
#include "hytlass/matrix_shape.h"
#include "hytlass/predicate_vector.h"
#include "hytlass/tensor_ref.h"
#include "hytlass/tensor_view.h"

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

namespace hytlass {
namespace conv {
namespace threadblock {

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

template <typename Shape_,
          typename OutputTileShape_,
          typename Element_,
          typename Layout_,
          typename ThreadMap_,
          typename AccessType_ = hytlass::AlignedArray<Element_, ThreadMap_::kElementsPerAccess> >
class DepthwiseFpropActivationDirect2dConvTileAccessIteratorOptimized {
 public:
  //
  // Types
  //

  using Shape = Shape_;
  using OutputTileShape = OutputTileShape_;
  using Element = Element_;
  using Layout = Layout_;
  using TensorCoord = typename Layout::TensorCoord;
  using ThreadMap = ThreadMap_;
  using AccessType = AccessType_;
  using TensorRef = hytlass::TensorRef<Element, Layout>;
  using Index = typename Layout::Index;
  using LongIndex = typename Layout::LongIndex;
  static IteratorAlgorithm const kIteratorAlgorithm = conv::IteratorAlgorithm::kOptimized;
  static StrideSupport const kStrideSupport = conv::StrideSupport::kStrided;
  static int const kConvDim = 2;
  using ConvProblemSize = typename conv::Conv2dProblemSize;

  static int const kAccessesPerVector = ThreadMap::kElementsPerAccess / AccessType::kElements;

  static_assert(!(ThreadMap::kElementsPerAccess % AccessType::kElements),
                "Vectors implied by the thread map must be divisible by the access type.");

  //
  // Simplifying assertions
  //
  static_assert(ThreadMap::Iterations::kContiguous == 1, "Require Iterations::kContiguous == 1");
  
  static_assert(OutputTileShape::kN == 1, "Require OutputTileShape::kN == 1");
  static_assert(OutputTileShape::kC == Shape::kColumn, "Require OutputTile shape == channels per threadblock");

  //
  // Parameters structure
  //

  using Params = Depthwise2dFpropDirectConvParams<Layout>;

 private:
  Conv2dProblemSize const &problem_size_;
  Params const &params_;
  char const *pointer_;

  // Base channels for current threadblock
  int base_c_;
  // Base activation index for current threadblock
  int offset_intial_npq_;
  // Base activation coord for current threadblock
  TensorCoord activatioin_base_;
  // Intial thread positioin
  int offset_initial_hwc_;
  // Overall load instruction per thread.
  int iterator_load_;
  // thread loading position.
  int iterator_hwc_;
  // Number of loads for activations tensor X.
  const int number_of_loads_;

 public:


  HYTLASS_HOST_DEVICE
  DepthwiseFpropActivationDirect2dConvTileAccessIteratorOptimized(
      Params const &params,
      Conv2dProblemSize const &problem_size,
      Element const *ptr,
      int thread_idx,
      MatrixCoord const &threadblock_offset =
          MatrixCoord()
      )
      : params_(params),
        problem_size_(problem_size),
        pointer_(reinterpret_cast<char const *>(ptr)),
        offset_intial_npq_(threadblock_offset.row()),
        offset_initial_hwc_(thread_idx),
        iterator_load_(0),
        number_of_loads_(params.activation_load_count) {
    
    base_c_ = threadblock_offset.column();

    set_activation_coord(offset_intial_npq_);

    set_iteration_index(0);
  }

  HYTLASS_HOST_DEVICE
  void set_activation_coord(int offset_npq) {
    int offset_inital_n, offset_inital_p, offset_inital_q;
    int residual;

    params_.pq_divmod(offset_inital_n, residual, offset_npq);
    params_.q_divmod(offset_inital_p, offset_inital_q, residual);

    int base_n = offset_inital_n;

    int base_h =
        offset_inital_p * OutputTileShape::kH * problem_size_.stride_h - problem_size_.pad_h;

    int base_w =
        offset_inital_q * OutputTileShape::kW * problem_size_.stride_w - problem_size_.pad_w;

    activatioin_base_ = TensorCoord(base_n, base_h, base_w, base_c_);
  }

  HYTLASS_HOST_DEVICE
  static Params getParams(Conv2dProblemSize const &problem_size, Layout const &layout) {
    return Params(
        problem_size,
        layout,
        {Shape::kRow, Shape::kColumn},
        {OutputTileShape::kN, OutputTileShape::kH, OutputTileShape::kW, OutputTileShape::kC},
        sizeof_bits<Element>::value,
        ThreadMap::kThreads,
        ThreadMap::Detail::ShapeVec::kContiguous,
        ThreadMap::kElementsPerAccess);
  }

  /// Overrides the internal iteration index
  HYTLASS_HOST_DEVICE
  void set_iteration_index(Index index) {
    iterator_hwc_ = offset_initial_hwc_ + index * ThreadMap::kThreads;
    iterator_load_ = index;
  }

  /// Adds a pointer offset in units of Element
  HYTLASS_HOST_DEVICE
  void add_pointer_offset(LongIndex pointer_offset) {
    pointer_ += pointer_offset * sizeof_bits<Element>::value / 8;
  }

  HYTLASS_HOST_DEVICE
  void advance() {
    // Go to next threadblock
    offset_intial_npq_ += problem_size_.split_k_slices;

    set_activation_coord(offset_intial_npq_);
  }

  /// Returns the coordinate in the activations tensor X that is currently pointed to
  /// by the iterator.
  HYTLASS_HOST_DEVICE
  TensorCoord at() const {
    
    int c = iterator_hwc_ %  ThreadMap::Detail::ShapeVec::kContiguous ;
    int next = iterator_hwc_ /  ThreadMap::Detail::ShapeVec::kContiguous ;
    int h, w;
    params_.activation_tile_w_divmod(h, w, next) ;

    c = c * AccessType::kElements;

    return activatioin_base_ + TensorCoord(0, h, w, c);
  }

  /// Returns true if the current coordinate is within the activations tensor X
  HYTLASS_HOST_DEVICE
  bool valid() const {
    TensorCoord coord = at();

    return coord.n() < problem_size_.N && coord.h() >= 0 && coord.h() < problem_size_.H &&
           coord.w() >= 0 && coord.w() < problem_size_.W && coord.c() < problem_size_.C;
  }

  /// Returns a pointer to the vector starting at the current coordinate
  HYTLASS_HOST_DEVICE
  AccessType const *get() const {
    TensorCoord coord = at();
    LongIndex offset = params_.layout(coord);

    AccessType const *ptr =
        reinterpret_cast<AccessType const *>(pointer_ + offset * sizeof_bits<Element>::value / 8);

    return ptr;
  }

  /// Increments to the next memory access
  HYTLASS_HOST_DEVICE
  DepthwiseFpropActivationDirect2dConvTileAccessIteratorOptimized &operator++() {

    ++iterator_load_;
    iterator_hwc_ += ThreadMap::kThreads;

    if (iterator_load_ < number_of_loads_) {
       return *this;
    }
    
    iterator_load_ = 0;
    iterator_hwc_ = offset_initial_hwc_;

    return *this;
  }

  /// Determines the activation size loaded by iterator
  HYTLASS_HOST_DEVICE
  int get_load_size() {
    return params_.activation_size;
  }

  /// Determines the iterations needed
  HYTLASS_HOST_DEVICE
  int get_iteration_num() {
    return number_of_loads_;
  }

  /// Determines whether the Depthwise fprop can execute the given problem.
  HYTLASS_HOST_DEVICE
  static Status can_implement(Conv2dProblemSize const &problem_size) {
    // check alignment constraint on iterator's contiguous dimension
    if (problem_size.C % AccessType::kElements) {
      return Status::kErrorInvalidProblem;
    }

    return Status::kSuccess;
  }
};

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

}  // namespace threadblock
}  // namespace conv
}  // namespace hytlass

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