partition.hpp#

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

namespace hpx

Functions

template<typename FwdIter, typename Pred, typename Proj = parallel::util::projection_identity> FwdIter partition(FwdIter first, FwdIter last, Pred &&pred, Proj &&proj = Proj())#

Reorders the elements in the range [first, last) in such a way that all elements for which the predicate pred returns true precede the elements for which the predicate pred returns false. Relative order of the elements is not preserved.

The assignments in the parallel partition algorithm invoked without an execution policy object execute in sequential order in the calling thread.

Note

Complexity: At most 2 * (last - first) swaps. Exactly last - first applications of the predicate and projection.

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 partition requires Pred to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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 unary predicate for partitioning the source iterators. The signature of this predicate should be equivalent to:
```
bool pred(const Type &a);
```
The signature does not need to have const&, but the function must not modify the objects passed to it. The type Type must be such that an object of type FwdIter can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate is invoked.

Returns

The partition algorithm returns returns FwdIter. The partition algorithm returns the iterator to the first element of the second group.

template<typename ExPolicy, typename FwdIter, typename Pred, typename Proj = parallel::util::projection_identity> parallel::util::detail::algorithm_result_t<ExPolicy, FwdIter> partition(ExPolicy &&policy, FwdIter first, FwdIter last, Pred &&pred, Proj &&proj = Proj())#

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

The assignments in the parallel partition 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: At most 2 * (last - first) swaps. Exactly last - first applications of the predicate and projection.

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 an forward iterator.
Pred – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of partition requires Pred to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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 unary predicate for partitioning the source iterators. The signature of this predicate should be equivalent to:
```
bool pred(const Type &a);
```
The signature does not need to have const&, but the function must not modify the objects passed to it. The type Type must be such that an object of type FwdIter can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate is invoked.

Returns

The partition algorithm returns a hpx::future<FwdIter> if the execution policy is of type parallel_task_policy and returns FwdIter otherwise. The partition algorithm returns the iterator to the first element of the second group.

template<typename BidirIter, typename F, typename Proj = parallel::util::projection_identity> BidirIter stable_partition(BidirIter first, BidirIter last, F &&f, Proj &&proj = Proj())#

Permutes the elements in the range [first, last) such that there exists an iterator i such that for every iterator j in the range [first, i) INVOKE(f, INVOKE (proj, *j)) != false, and for every iterator k in the range [i, last), INVOKE(f, INVOKE (proj, *k)) == false

The invocations of f in the parallel stable_partition algorithm invoked without an execution policy object executes in sequential order in the calling thread.

Note

Complexity: At most (last - first) * log(last - first) swaps, but only linear number of swaps if there is enough extra memory. Exactly last - first applications of the predicate and projection.

Template Parameters

BidirIter – The type of the source iterators used (deduced). This iterator type must meet the requirements of a bidirectional iterator.
F – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of transform requires F to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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.
f – Unary predicate which returns true if the element should be ordered before other elements. Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
bool fun(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type BidirIter can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate f is invoked.

Returns

The stable_partition algorithm returns an iterator i such that for every iterator j in the range [first, i), f(*j) != false INVOKE(f, INVOKE(proj, *j)) != false, and for every iterator k in the range [i, last), f(*k) == false INVOKE(f, INVOKE (proj, *k)) == false. The relative order of the elements in both groups is preserved.

template<typename ExPolicy, typename BidirIter, typename F, typename Proj = parallel::util::projection_identity> parallel::util::detail::algorithm_result_t<ExPolicy, BidirIter> stable_partition(ExPolicy &&policy, BidirIter first, BidirIter last, F &&f, Proj &&proj = Proj())#

The invocations of f in the parallel stable_partition algorithm invoked with an execution policy object of type sequenced_policy executes in sequential order in the calling thread.

The invocations of f in the parallel stable_partition 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: At most (last - first) * log(last - first) swaps, but only linear number of swaps if there is enough extra memory. Exactly last - first applications of the predicate and projection.

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 invocations of f.
BidirIter – The type of the source iterators used (deduced). This iterator type must meet the requirements of a bidirectional iterator.
F – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of transform requires F to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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.
f – Unary predicate which returns true if the element should be ordered before other elements. Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
bool fun(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type BidirIter can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate f is invoked.

Returns

template<typename FwdIter1, typename FwdIter2, typename FwdIter3, typename Pred, typename Proj = parallel::util::projection_identity> std::pair<FwdIter2, FwdIter3> partition_copy(FwdIter1 first, FwdIter1 last, FwdIter2 dest_true, FwdIter3 dest_false, Pred &&pred, fProj &&proj = Proj())#

Copies the elements in the range, defined by [first, last), to two different ranges depending on the value returned by the predicate pred. The elements, that satisfy the predicate pred are copied to the range beginning at dest_true. The rest of the elements are copied to the range beginning at dest_false. The order of the elements is preserved.

The assignments in the parallel partition_copy algorithm invoked without an execution policy object execute in sequential order in the calling thread.

Note

Complexity: Performs not more than last - first assignments, exactly last - first applications of the predicate pred.

Template Parameters

FwdIter1 – The type of the source iterators used (deduced). This iterator type must meet the requirements of an forward iterator.
FwdIter2 – The type of the iterator representing the destination range for the elements that satisfy the predicate pred (deduced). This iterator type must meet the requirements of an forward iterator.
FwdIter3 – The type of the iterator representing the destination range for the elements that don’t satisfy the predicate pred (deduced). This iterator type must meet the requirements of an forward iterator.
Pred – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of partition_copy requires Pred to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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.
dest_true – Refers to the beginning of the destination range for the elements that satisfy the predicate pred
dest_false – Refers to the beginning of the destination range for the elements that don’t satisfy the predicate pred.
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 unary predicate for partitioning the source iterators. The signature of this predicate should be equivalent to:
```
bool pred(const Type &a);
```
The signature does not need to have const&, but the function must not modify the objects passed to it. The type Type must be such that an object of type FwdIter1 can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate is invoked.

Returns

The partition_copy algorithm returns std::pair<OutIter1, OutIter2>. The partition_copy algorithm returns the pair of the destination iterator to the end of the dest_true range, and the destination iterator to the end of the dest_false range.

template<typename ExPolicy, typename FwdIter1, typename FwdIter2, typename FwdIter3, typename Pred, typename Proj = parallel::util::projection_identity> parallel::util::detail::algorithm_result_t<ExPolicy, std::pair<FwdIter2, FwdIter3>> partition_copy(ExPolicy &&policy, FwdIter1 first, FwdIter1 last, FwdIter2 dest_true, FwdIter3 dest_false, Pred &&pred, Proj &&proj = Proj())#

Copies the elements in the range, defined by [first, last), to two different ranges depending on the value returned by the predicate pred. The elements, that satisfy the predicate pred, are copied to the range beginning at dest_true. The rest of the elements are copied to the range beginning at dest_false. The order of the elements is preserved.

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

The assignments in the parallel partition_copy 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 applications of the predicate pred.

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.
FwdIter1 – The type of the source iterators used (deduced). This iterator type must meet the requirements of an forward iterator.
FwdIter2 – The type of the iterator representing the destination range for the elements that satisfy the predicate pred (deduced). This iterator type must meet the requirements of an forward iterator.
FwdIter3 – The type of the iterator representing the destination range for the elements that don’t satisfy the predicate pred (deduced). This iterator type must meet the requirements of an forward iterator.
Pred – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of partition_copy requires Pred to meet the requirements of CopyConstructible.
Proj – The type of an optional projection function. This defaults to util::projection_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.
dest_true – Refers to the beginning of the destination range for the elements that satisfy the predicate pred
dest_false – Refers to the beginning of the destination range for the elements that don’t satisfy the predicate pred.
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 unary predicate for partitioning the source iterators. The signature of this predicate should be equivalent to:
```
bool pred(const Type &a);
```
The signature does not need to have const&, but the function must not modify the objects passed to it. The type Type must be such that an object of type FwdIter1 can be dereferenced and then implicitly converted to Type.
proj – Specifies the function (or function object) which will be invoked for each of the elements as a projection operation before the actual predicate is invoked.

Returns

The partition_copy algorithm returns a hpx::future<std::pair<OutIter1, OutIter2>> if the execution policy is of type parallel_task_policy and returns std::pair<OutIter1, OutIter2> otherwise. The partition_copy algorithm returns the pair of the destination iterator to the end of the dest_true range, and the destination iterator to the end of the dest_false range.