count_if

Header: <Kokkos_StdAlgorithms.hpp>

Description

Returns the number of elements in a range or in rank-1 View that satisfy a given unary prediate.

Interface

Warning

This is currently inside the Kokkos::Experimental namespace.

Overload set accepting execution space

template <class ExecutionSpace, class IteratorType, class Predicate>
typename IteratorType::difference_type count_if(const ExecutionSpace& exespace,
                                                IteratorType first,
                                                IteratorType last,                   (1)
                                                Predicate pred);


template <class ExecutionSpace, class IteratorType, class Predicate>
typename IteratorType::difference_type count_if(const std::string& label,
                                                const ExecutionSpace& exespace,
                                                IteratorType first,                  (2)
                                                IteratorType last,
                                                Predicate pred);

template <class ExecutionSpace, class DataType, class... Properties,
          class Predicate>
auto count_if(const ExecutionSpace& exespace,
              const ::Kokkos::View<DataType, Properties...>& view,                   (3)
              Predicate pred);

template <class ExecutionSpace, class DataType, class... Properties,
          class Predicate>
auto count_if(const std::string& label, const ExecutionSpace& exespace,
              const ::Kokkos::View<DataType, Properties...>& view,                   (4)
              Predicate pred);

Overload set accepting a team handle

Added in version 4.2.

template <class TeamHandleType, class IteratorType, class Predicate>
KOKKOS_FUNCTION
typename IteratorType::difference_type count_if(const TeamHandleType& teamHandle,
                                                IteratorType first,
                                                IteratorType last,                   (5)
                                                Predicate pred);

template <class TeamHandleType, class DataType, class... Properties,
          class Predicate>
KOKKOS_FUNCTION
auto count_if(const TeamHandleType& teamHandle,
              const ::Kokkos::View<DataType, Properties...>& view,                   (6)
              Predicate pred);

Parameters and Requirements

• exespace: execution space instance

• teamHandle: team handle instance given inside a parallel region when using a TeamPolicy

• label: string forwarded to internal parallel kernels for debugging purposes

  • 1: The default string is “Kokkos::count_if_iterator_api_default”.

  • 3: The default string is “Kokkos::count_if_view_api_default”.

  • NOTE: overloads accepting a team handle do not use a label internally

• first, last: range of elements to search in

  • must be random access iterators, e.g., returned from Kokkos::Experimental::(c)begin/(c)end

  • must represent a valid range, i.e., last >= first

  • must be accessible from exespace or from the execution space associated with the team handle

• view:

  • must be rank-1, and have LayoutLeft, LayoutRight, or LayoutStride

  • must be accessible from exespace or from the execution space associated with the team handle

• pred: unary functor returning true if an argument satisfies the desired condition.

  pred(v) must be valid to be called from the execution space passed, or the execution space associated with the team handle, and convertible to bool for every argument v of type value_type, where value_type is the value type of IteratorType or view and must not modify v.

  • must conform to:

  struct CustomPredicate{
    KOKKOS_INLINE_FUNCTION
    bool operator()(const value_type & v) const {
      return /* true if v satisfies your desired condition */;
    }
  };
  

Return Value

Returns the number of elements in the range first,last or in view for which the predicate is true.