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/*! \file
  \brief PredicatedTileIteratorPredicates.

  PredicatedTileIteratorPredicates enables both upper and lower bounds for predicates.

*/

#pragma once

#include "hytlass/hytlass.h"
#include "hytlass/numeric_types.h"
#include "hytlass/array.h"
#include "hytlass/layout/matrix.h"
#include "hytlass/layout/tensor.h"
#include "hytlass/matrix_shape.h"
#include "hytlass/tensor_ref.h"
#include "hytlass/transform/pitch_linear_thread_map.h"
#include "hytlass/epilogue/threadblock/output_tile_thread_map.h"
#include "hytlass/arch/arch.h"
#include "hytlass/arch/memory.h"
#include "hytlass/epilogue/threadblock/predicated_tile_iterator_params.h"

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

namespace hytlass {

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

namespace epilogue {
namespace threadblock {

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

/// Tile iterator predicates used to bound computations in epilogue.
///
/// Satisfies: ReadableTileIterator | PredicatedTileIterator | ForwardTileIterator
///
template <
  typename ThreadMap_,       ///< Thread map (conept: OutputTileThreadMap)
  typename Element_          ///< Element data type
>
class PredicatedTileIteratorPredicates {
public:
  using ThreadMap = ThreadMap_;
  using Shape = typename ThreadMap::Shape;

  using Element = Element_;

  using Layout = layout::RowMajor;
  using TensorRef = TensorRef<Element, Layout>;
  using ConstTensorRef = typename TensorRef::ConstTensorRef;

  using Index = typename Layout::Index;
  using LongIndex = typename Layout::LongIndex;
  using TensorCoord = MatrixCoord;

  static int const kElementsPerAccess = ThreadMap::kElementsPerAccess;
  static int const kThreads = ThreadMap::kThreads;
  static int const kIterations = ThreadMap::Count::kTile;

  static_assert( ThreadMap::Iterations::kRow > 0,"ThreadMap::Iterations::kRow must be > 0");
  static_assert( ThreadMap::Iterations::kGroup > 0,"ThreadMap::Iterations::kGroup must be > 0");
  static_assert( ThreadMap::Iterations::kCluster > 0,"ThreadMap::Iterations::kCluster must be > 0");
  static_assert( ThreadMap::Iterations::kColumn > 0,"ThreadMap::Iterations::kColumn must be > 0");

  /// Fragment object
  using Fragment = Array<
    Element, 
    ThreadMap::Iterations::kColumn * 
    ThreadMap::Iterations::kRow * 
    ThreadMap::Iterations::kGroup * 
    ThreadMap::Iterations::kCluster * ThreadMap::kElementsPerAccess>;

  /// Memory access size
  using AccessType = AlignedArray<Element, ThreadMap::kElementsPerAccess>;

  //
  // Parameters struct
  //

  /// Uses a non-template class
  struct Params : PredicatedTileIteratorParams {

    HYTLASS_HOST_DEVICE
    Params() { }

    HYTLASS_HOST_DEVICE
    Params(Layout const &layout): 
      PredicatedTileIteratorParams(
        layout.stride(0) * int(sizeof(AccessType)) / kElementsPerAccess,
        make_OutputTileThreadMapDesc<ThreadMap>()
      ) 
    {
        
    }
  };

  /// Mask object
  struct Mask {

    static int const kCount = ThreadMap::Iterations::kColumn;

    /// Predicate state
    bool predicates[kCount];

    //
    // Mask
    //
    HYTLASS_HOST_DEVICE
    Mask() {
      enable();
    }

    ///< Efficiently disables all accesses guarded by mask
    HYTLASS_HOST_DEVICE void clear() {
      HYTLASS_PRAGMA_UNROLL
      for (int i = 0; i < kCount; ++i) {
        predicates[i] = false;
      }
    }

    ///< HYTLASS_HOST_DEVICE enables all accesses guarded by mask
    HYTLASS_DEVICE void enable() {
      HYTLASS_PRAGMA_UNROLL
      for (int i = 0; i < kCount; ++i) {
        predicates[i] = true;
      }
    }
  };

private:

  //
  // Data members
  //

  /// Parameters structure containing reference and precomputed state.
  PredicatedTileIteratorParams params_;

  /// Array of boolean values to contain steady-state predicates
  Mask mask_;

  /// Extent of the matrix tile in rows
  Index lower_extent_row_;
  Index upper_extent_row_;

  /// A thread's starting row position (assuming steady-state predicates have been computed)
  Index thread_start_row_;

  /// Internal state counter
  int state_[3];
 
  //
  // Static asserts about internal strides
  //

  static_assert(sizeof(lower_extent_row_) == 4, "Expected 32b extents");
  static_assert(sizeof(upper_extent_row_) == 4, "Expected 32b extents");
  static_assert(sizeof(thread_start_row_) == 4, "Expected 32b extents");
  static_assert(sizeof(PredicatedTileIteratorParams::stride) == 8, "Expected 64b strides");

private:

  //
  // Methods
  //

public:

  //
  // Methods
  //

  /// Constructor
  HYTLASS_DEVICE
  PredicatedTileIteratorPredicates(
    PredicatedTileIteratorParams const & params,
    TensorCoord lower_extent,
    TensorCoord upper_extent,
    int thread_idx,
    TensorCoord threadblock_offset = TensorCoord()
  ): 
    params_(params)
  {

    TensorCoord thread_offset = ThreadMap::initial_offset(thread_idx) + threadblock_offset;

    lower_extent_row_ = lower_extent.row();
    upper_extent_row_ = upper_extent.row();
    thread_start_row_ = thread_offset.row();

    // Initialize predicates
    HYTLASS_PRAGMA_UNROLL
    for (int c = 0; c < ThreadMap::Iterations::kColumn; ++c) {

      mask_.predicates[c] = ((thread_offset.column() 
        + ThreadMap::Delta::kColumn * c) < upper_extent.column()) &&
        ((thread_offset.column() + ThreadMap::Delta::kColumn * c) >= lower_extent.column());
    }

    // Initialize internal state counter
    state_[0] = state_[1] = state_[2] = 0;
  }

  /// Advances to the next position to load or store
  HYTLASS_HOST_DEVICE
  PredicatedTileIteratorPredicates &operator++() {

    ++state_[0];
    thread_start_row_ += ThreadMap::Shape::kRow;

    if (state_[0] == ThreadMap::Count::kRow) {

      state_[0] = 0;
      ++state_[1];

      thread_start_row_ += (ThreadMap::Shape::kGroup - 1) *
        ThreadMap::Shape::kRow * ThreadMap::Count::kRow;

      if (state_[1] == ThreadMap::Count::kGroup) {

        state_[1] = 0;
        ++state_[2];

        thread_start_row_ += ThreadMap::Count::kGroup *
          ThreadMap::Shape::kGroup * ThreadMap::Count::kRow * ThreadMap::Shape::kRow;

        if (state_[2] == ThreadMap::Count::kCluster) {
          state_[2] = 0;
        }
      }
    }

    return *this;
  }

  ///< Efficiently disables all accesses guarded by mask
  HYTLASS_DEVICE void clear_mask() {
    mask_.clear();
  }

  ///< Efficiently enables all accesses guarded by mask
  HYTLASS_DEVICE void enable_mask() {
    mask_.enable();
  }

  ///< Gets the mask
  HYTLASS_DEVICE void get_mask(Mask &mask) {
    mask = mask_;
  }

  ///< Sets the mask
  HYTLASS_DEVICE void set_mask(Mask const &mask) {
    mask_ = mask;
  }

  ///< Gets lower_extent_row_
  HYTLASS_DEVICE Index get_lower_extent_row() {
    return lower_extent_row_;
  }

  ///< Gets upper_extent_row_
  HYTLASS_DEVICE Index get_upper_extent_row() {
    return upper_extent_row_;
  }

  ///< Gets thread_start_row_
  HYTLASS_DEVICE Index get_thread_start_row() {
    return thread_start_row_;
  }
};

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

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

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