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[oneDPL] Add memory parallel range algorithms #631

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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ The following differences to the standard C++ range algorithms apply:
In that case, the returned value contains iterators pointing to the positions past the last elements
processed according to the algorithm semantics.
- ``for_each`` does not return its function object.
- ``destroy`` is not marked with ``noexcept``.

Except for these differences, the signatures of parallel range algorithms correspond to the working draft
of the next edition of the C++ standard (C++26).
Expand All @@ -46,9 +47,22 @@ of parallel range algorithms.
.. code:: cpp
// C++20 analogue of std::projected_value_t; exposition only
template<typename I, typename Proj>
template <typename I, typename Proj>
using /*projected-value-type*/ = std::remove_cvref_t<std::invoke_result_t<Proj&, std::iter_value_t<I>&>>;
// C++20 analogue of nothrow-random-access-range in the C++26 working draft; exposition only
// Semantic requirements are listed further below
template <typename R>
concept nothrow-random-access-range =
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why did we decide to "copy" this concept instead of nothrow-sized-random-access-range?

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I think for consistency with the other signatures, where sized_range comes under requires clauses.

std::ranges::random_access_range<R> &&
std::is_lvalue_reference_v<std::iter_reference_t<std::ranges::iterator_t<R>>> &&
std::same_as<std::remove_cvref_t<std::iter_reference_t<std::ranges::iterator_t<R>>>,
std::iter_value_t<std::ranges::iterator_t<R>>>;
A type ``R`` models ``nothrow-random-access-range`` if no exceptions are thrown from
any operation on an object of type ``std::ranges::iterator_t<R>``
required by the ``std::random_access_iterator`` concept.

Whole Sequence Operations
+++++++++++++++++++++++++

Expand Down Expand Up @@ -526,5 +540,69 @@ In-place Mutating Operations
}
Uninitialized Memory Algorithms
+++++++++++++++++++++++++++++++

.. code:: cpp
// Defined in <oneapi/dpl/memory>
namespace oneapi::dpl::ranges {
// uninitialized_default_construct
template <typename ExecutionPolicy, /*nothrow-random-access-range*/ R>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<R> &&
std::default_initializable<std::ranges::range_value_t<R>>
std::ranges::borrowed_iterator_t<R>
uninitialized_default_construct (ExecutionPolicy&& pol, R&& r);
// uninitialized_value_construct
template <typename ExecutionPolicy, /*nothrow-random-access-range*/ R>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<R> &&
std::default_initializable<std::ranges::range_value_t<R>>
std::ranges::borrowed_iterator_t<R>
uninitialized_value_construct (ExecutionPolicy&& pol, R&& r);
// uninitialized_copy
template <typename ExecutionPolicy, std::random_access_range IR,
/*nothrow-random-access-range*/ OR>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<IR> && std::ranges::sized_range<OR> &&
std::constructible_from<std::ranges::range_value_t<OR>,
std::ranges::range_reference_t<IR>>
std::ranges::uninitialized_copy_result<std::ranges::borrowed_iterator_t<IR>,
std::ranges::borrowed_iterator_t<OR>>
uninitialized_copy (ExecutionPolicy&& pol, IR&& in_range, OR&& out_range);
// uninitialized_move
template <typename ExecutionPolicy, std::ranges::random_access_range IR,
/*nothrow-random-access-range*/ OR>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<IR> && std::ranges::sized_range<OR> &&
std::constructible_from<std::ranges::range_value_t<OR>,
std::ranges::range_rvalue_reference_t<IR>>
std::ranges::uninitialized_move_result<std::ranges::borrowed_iterator_t<IR>,
std::ranges::borrowed_iterator_t<OR>>
uninitialized_move (ExecutionPolicy&& pol, IR&& in_range, OR&& out_range);
// uninitialized_fill
template <typename ExecutionPolicy, /*nothrow-random-access-range*/ R, typename T>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<R> &&
std::constructible_from<std::ranges::range_value_t<R>, const T&>
std::ranges::borrowed_iterator_t<R>
uninitialized_fill (ExecutionPolicy&& pol, R&& r, const T& value);
Comment on lines +593 to +599
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@akukanov akukanov Aug 18, 2025

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For uninitialized_fill we should also add the default type for typename T, similarly to fill. According to @rarutyun this was inadvertently forgotten by the author of that proposal, and we have not spotted it in P3179, only later.

// destroy
template <typename ExecutionPolicy, /*nothrow-random-access-range*/ R>
requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
std::ranges::sized_range<R> &&
std::destructible<std::ranges::range_value_t<R>>
std::ranges::borrowed_iterator_t<R>
destroy (ExecutionPolicy&& pol, R&& r);
}
.. _`C++ Standard`: https://isocpp.org/std/the-standard
.. _`SYCL`: https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html
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