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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 _CCCL_HAS_CUDA_COMPILER
#  include <thrust/system/cuda/config.h>

#  include <thrust/distance.h>
#  include <thrust/iterator/transform_iterator.h>
#  include <thrust/system/cuda/detail/reduce.h>
#  include <thrust/system/cuda/detail/util.h>

THRUST_NAMESPACE_BEGIN
namespace cuda_cub
{

template <class Derived, class InputIt, class UnaryPred>
typename iterator_traits<InputIt>::difference_type _CCCL_HOST_DEVICE
count_if(execution_policy<Derived>& policy, InputIt first, InputIt last, UnaryPred unary_pred)
{
  using size_type       = typename iterator_traits<InputIt>::difference_type;
  using flag_iterator_t = transform_iterator<UnaryPred, InputIt, size_type, size_type>;

  return cuda_cub::reduce_n(
    policy, flag_iterator_t(first, unary_pred), thrust::distance(first, last), size_type(0), plus<size_type>());
}

template <class Derived, class InputIt, class Value>
typename iterator_traits<InputIt>::difference_type _CCCL_HOST_DEVICE
count(execution_policy<Derived>& policy, InputIt first, InputIt last, Value const& value)
{
  return cuda_cub::count_if(policy, first, last, thrust::detail::equal_to_value<Value>(value));
}

} // namespace cuda_cub
THRUST_NAMESPACE_END
#endif
