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 * provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
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 *       conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
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#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/coord.h"

namespace cutlass {
namespace reference {
namespace device {
namespace kernel {

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

/// Defines several helpers
namespace detail {

/// Helper to perform for-each operation
template <typename Func, int Rank, int RankRemaining>
struct TensorForEachHelper {

  /// Constructor for general rank
  __inline__ __device__
  TensorForEachHelper(Func &func, Coord<Rank> const &size, Coord<Rank> &coord, int64_t index) {

    int64_t product = 1;

    CUTLASS_PRAGMA_UNROLL
    for (int i = Rank - RankRemaining; i < Rank; ++i) {
      product *= size[i];
    }

    coord[Rank - 1 - RankRemaining] = index / product;
    int64_t remaining = index % product;
    
    TensorForEachHelper<Func, Rank, RankRemaining-1>(func, size, coord, remaining);
  }
};

/// Helper to perform for-each operation
template <typename Func, int Rank>
struct TensorForEachHelper<Func, Rank, 0> {

  /// Constructor for fastest chaning rank
  __inline__ __device__
  TensorForEachHelper(Func &func, Coord<Rank> const &size, Coord<Rank> &coord, int64_t index) {

    coord[Rank - 1] = index;

    if (coord < size) {
      func(coord);
    }
  }
};

} // namespace detail

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

/// Helper to perform for-each operation
template <typename Func, int Rank, typename Params>
__global__ void TensorForEach(Coord<Rank> size, Params params = Params()) {

  Func func(params);

  int64_t index = threadIdx.x + blockIdx.x * blockDim.x;
  int64_t max_index = 1;

  CUTLASS_PRAGMA_UNROLL
  for (int i = 0; i < Rank; ++i) {
    max_index *= size[i];
  }

  CUTLASS_PRAGMA_NO_UNROLL
  while  (index < max_index) {
    Coord<Rank> coord;

    detail::TensorForEachHelper<Func, Rank, Rank - 1>(func, size, coord, index); 
    index += blockDim.x * gridDim.x;
  }
}

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

} // namespace kernel
} // namespace device
} // namespace reference
} // namespace cutlass