Function template count

hpx::parallel::v1::count

Synopsis

// In header: <hpx/parallel/detail/count.hpp>


template<typename ExPolicy, typename InIter, typename T> 
  unspecified count(ExPolicy && policy, InIter first, InIter last, 
                    T const & value);

Description

Returns the number of elements in the range [first, last) satisfying a specific criteria. This version counts the elements that are equal to the given value.

	Note
	Complexity: Performs exactly last - first comparisons.

The comparisons in the parallel count algorithm invoked with an execution policy object of type sequential_execution_policy execute in sequential order in the calling thread.

	Note
	The comparisons in the parallel count algorithm invoked with an execution policy object of type `parallel_execution_policy` or `task_execution_policy` are permitted to execute in an unordered fashion in unspecified threads, and indeterminately sequenced within each thread.

Parameters:

`first`	Refers to the beginning of the sequence of elements the algorithm will be applied to.
`last`	Refers to the end of the sequence of elements the algorithm will be applied to.
`policy`	The execution policy to use for the scheduling of the iterations.
`value`	The value to search for.

Template Parameters:

`ExPolicy`	The type of the execution policy to use (deduced). It describes the manner in which the execution of the algorithm may be parallelized and the manner in which it executes the comparisons.
`InIter`	The type of the source iterators used (deduced). This iterator type must meet the requirements of an input iterator.
`T`	The type of the value to search for (deduced).

Returns:

The count algorithm returns a hpx::future<difference_type> if the execution policy is of type task_execution_policy and returns difference_type otherwise (where difference_type is defined by std::iterator_traits<InIter>::difference_type. The count algorithm returns the number of elements satisfying the given criteria.