TheRock/rocm-libraries/projects/rocthrust/thrust/system/hip/detail/reduce.h

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#pragma once

#include <thrust/detail/config.h>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#if THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP

#  include <thrust/system/hip/config.h>

#  include <thrust/detail/alignment.h>
#  include <thrust/detail/minmax.h>
#  include <thrust/detail/raw_reference_cast.h>
#  include <thrust/detail/temporary_array.h>
#  include <thrust/detail/type_traits/iterator/is_output_iterator.h>
#  include <thrust/distance.h>
#  include <thrust/functional.h>
#  include <thrust/system/hip/detail/dispatch.h>
#  include <thrust/system/hip/detail/general/temp_storage.h>
#  include <thrust/system/hip/detail/get_value.h>
#  include <thrust/system/hip/detail/par_to_seq.h>
#  include <thrust/system/hip/detail/util.h>

#  include <cstdint>

// rocprim include
#  include <rocprim/rocprim.hpp>

THRUST_NAMESPACE_BEGIN

// forward declare generic reduce
// to circumvent circular dependency
template <typename DerivedPolicy, typename InputIterator, typename T, typename BinaryFunction>
T THRUST_HOST_DEVICE
reduce(const thrust::detail::execution_policy_base<DerivedPolicy>& exec,
       InputIterator first,
       InputIterator last,
       T init,
       BinaryFunction binary_op);

namespace hip_rocprim
{

namespace __reduce
{

template <typename Derived, typename InputIt, typename Size, typename T, typename BinaryOp>
THRUST_RUNTIME_FUNCTION T
reduce(execution_policy<Derived>& policy, InputIt first, Size num_items, T init, BinaryOp binary_op)
{
  using namespace thrust::system::hip_rocprim::temp_storage;
  if (num_items == 0)
  {
    return init;
  }

  size_t temp_storage_bytes = 0;
  hipStream_t stream        = hip_rocprim::stream(policy);
  bool debug_sync           = THRUST_HIP_DEBUG_SYNC_FLAG;

  // Determine temporary device storage requirements.
  hip_rocprim::throw_on_error(
    rocprim::reduce(
      nullptr,
      temp_storage_bytes,
      first,
      static_cast<T*>(nullptr),
      init,
      static_cast<size_t>(num_items),
      binary_op,
      stream,
      debug_sync),
    "reduce failed on 1st step");

  size_t storage_size = 0;
  void* ptr       = nullptr;
  void* temp_stor = nullptr;
  T* d_result;

  auto l_part = make_linear_partition(make_partition(&temp_stor, temp_storage_bytes), ptr_aligned_array(&d_result, 1));

  // Calculate storage_size including alignment
  hip_rocprim::throw_on_error(partition(ptr, storage_size, l_part));

  // Allocate temporary storage.
  thrust::detail::temporary_array<std::uint8_t, Derived> tmp(policy, storage_size);
  ptr = static_cast<void*>(tmp.data().get());

  // Create pointers with alignment
  hip_rocprim::throw_on_error(partition(ptr, storage_size, l_part));

  hip_rocprim::throw_on_error(
    rocprim::reduce(
      ptr, temp_storage_bytes, first, d_result, init, static_cast<size_t>(num_items), binary_op, stream, debug_sync),
    "reduce failed on 2nd step");

  T result = hip_rocprim::get_value(policy, d_result);

  return result;
}
} // namespace __reduce

//-------------------------
// Thrust API entry points
//-------------------------

THRUST_EXEC_CHECK_DISABLE
template <typename Derived, typename InputIt, typename Size, typename T, typename BinaryOp>
THRUST_HOST_DEVICE T
reduce_n(execution_policy<Derived>& policy, InputIt first, Size num_items, T init, BinaryOp binary_op)
{
  // struct workaround is required for HIP-clang
  struct workaround
  {
    THRUST_HOST static T
    par(execution_policy<Derived>& policy, InputIt first, Size num_items, T init, BinaryOp binary_op)
    {
      return init = __reduce::reduce(policy, first, num_items, init, binary_op);
    }
#  if !__THRUST_HAS_HIPRT__
    THRUST_DEVICE static T
    seq(execution_policy<Derived>& policy, InputIt first, Size num_items, T init, BinaryOp binary_op)
    {
      return init = thrust::reduce(cvt_to_seq(derived_cast(policy)), first, first + num_items, init, binary_op);
    }
#  endif
  };
#  if __THRUST_HAS_HIPRT__
  return workaround::par(policy, first, num_items, init, binary_op);
#  else
  return workaround::seq(policy, first, num_items, init, binary_op);
#  endif
}

template <class Derived, class InputIt, class T, class BinaryOp>
THRUST_HOST_DEVICE T reduce(execution_policy<Derived>& policy, InputIt first, InputIt last, T init, BinaryOp binary_op)
{
  using size_type = typename iterator_traits<InputIt>::difference_type;
  // FIXME: Check for RA iterator.
  size_type num_items = static_cast<size_type>(thrust::distance(first, last));
  return hip_rocprim::reduce_n(policy, first, num_items, init, binary_op);
}

template <class Derived, class InputIt, class T>
THRUST_HOST_DEVICE T reduce(execution_policy<Derived>& policy, InputIt first, InputIt last, T init)
{
  return hip_rocprim::reduce(policy, first, last, init, plus<T>());
}

template <class Derived, class InputIt>
THRUST_HOST_DEVICE typename iterator_traits<InputIt>::value_type
reduce(execution_policy<Derived>& policy, InputIt first, InputIt last)
{
  using value_type = typename iterator_traits<InputIt>::value_type;
  return hip_rocprim::reduce(policy, first, last, value_type(0));
}

} // namespace hip_rocprim

THRUST_NAMESPACE_END

#  include <thrust/memory.h>
#  include <thrust/reduce.h>

#endif