hpx::unique

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hpx::unique#

Defined in header hpx/algorithm.hpp.

See Public API for a list of names and headers that are part of the public HPX API.

See also:

template<typename FwdIter, typename Pred = hpx::parallel::detail::equal_to, typename Proj = hpx::identity>
FwdIter hpx::unique(FwdIter first, FwdIter last, Pred &&pred = Pred(), Proj &&proj = Proj())#

Eliminates all but the first element from every consecutive group of equivalent elements from the range [first, last) and returns a past-the-end iterator for the new logical end of the range.

Note

Complexity: Performs not more than last - first assignments, exactly last - first - 1 applications of the predicate pred and no more than twice as many applications of the projection proj.

Template Parameters:

  • FwdIter – The type of the source iterators used (deduced). This iterator type must meet the requirements of a forward iterator.

  • Pred – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of unique requires Pred to meet the requirements of CopyConstructible. This defaults to std::equal_to<>

  • Proj – The type of an optional projection function. This defaults to hpx::identity.

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.

  • pred – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). This is an binary predicate which returns true for the required elements. The signature of this predicate should be equivalent to: 

    bool pred(const Type1 &a, const Type2 &b);
    The signature does not need to have const&, but the function must not modify the objects passed to it. The types Type1 and Type2 must be such that objects of types FwdIter can be dereferenced and then implicitly converted to both Type1 and Type2

  • proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate pred is invoked.

Returns:

The unique algorithm returns FwdIter. The unique algorithm returns the iterator to the new end of the range.

template<typename ExPolicy, typename FwdIter, typename Pred = hpx::parallel::detail::equal_to, typename Proj = hpx::identity>
parallel::util::detail::algorithm_result<ExPolicy, FwdIter>::type hpx::unique(ExPolicy &&policy, FwdIter first, FwdIter last, Pred &&pred = Pred(), Proj &&proj = Proj())#

Eliminates all but the first element from every consecutive group of equivalent elements from the range [first, last) and returns a past-the-end iterator for the new logical end of the range. Executed according to the policy.

The assignments in the parallel unique algorithm invoked with an execution policy object of type sequenced_policy execute in sequential order in the calling thread.

The assignments in the parallel unique algorithm invoked with an execution policy object of type parallel_policy or parallel_task_policy are permitted to execute in an unordered fashion in unspecified threads, and indeterminately sequenced within each thread.

Note

Complexity: Performs not more than last - first assignments, exactly last - first - 1 applications of the predicate pred and no more than twice as many applications of the projection proj.

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 assignments.

  • FwdIter – The type of the source iterators used (deduced). This iterator type must meet the requirements of a forward iterator.

  • Pred – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of unique requires Pred to meet the requirements of CopyConstructible. This defaults to std::equal_to<>

  • Proj – The type of an optional projection function. This defaults to hpx::identity.

Parameters:

  • policy – The execution policy to use for the scheduling of the iterations.

  • 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.

  • pred – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). This is an binary predicate which returns true for the required elements. The signature of this predicate should be equivalent to: 

    bool pred(const Type1 &a, const Type2 &b);
    The signature does not need to have const&, but the function must not modify the objects passed to it. The types Type1 and Type2 must be such that objects of types FwdIter can be dereferenced and then implicitly converted to both Type1 and Type2

  • proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate pred is invoked.

Returns:

The unique algorithm returns a hpx::future<FwdIter> if the execution policy is of type sequenced_task_policy or parallel_task_policy and returns FwdIter otherwise. The unique algorithm returns the iterator to the new end of the range.

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