cuda_toolkit/include/thrust/system/cuda/detail/count.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_NVCC
#include <thrust/system/cuda/config.h>

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

THRUST_NAMESPACE_BEGIN
namespace cuda_cub {

template <class Derived,
          class InputIt,
          class UnaryPred>
typename iterator_traits<InputIt>::difference_type __host__ __device__
count_if(execution_policy<Derived> &policy,
         InputIt                    first,
         InputIt                    last,
         UnaryPred                  unary_pred)
{
  typedef typename iterator_traits<InputIt>::difference_type size_type;
  typedef transform_input_iterator_t<size_type,
                                     InputIt,
                                     UnaryPred>
      flag_iterator_t;

  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 __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