__pstl/cpu_algos/merge.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___PSTL_CPU_ALGOS_MERGE_H
0010 #define _LIBCPP___PSTL_CPU_ALGOS_MERGE_H
0011
0012 #include <__algorithm/merge.h>
0013 #include <__assert>
0014 #include <__config>
0015 #include <__iterator/concepts.h>
0016 #include <__pstl/backend_fwd.h>
0017 #include <__pstl/cpu_algos/cpu_traits.h>
0018 #include <__type_traits/is_execution_policy.h>
0019 #include <__utility/move.h>
0020 #include <optional>
0021
0022 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0023 #  pragma GCC system_header
0024 #endif
0025
0026 _LIBCPP_PUSH_MACROS
0027 #include <__undef_macros>
0028
0029 #if _LIBCPP_STD_VER >= 17
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032 namespace __pstl {
0033
0034 template <class _Backend, class _RawExecutionPolicy>
0035 struct __cpu_parallel_merge {
0036   template <class _Policy, class _ForwardIterator1, class _ForwardIterator2, class _ForwardOutIterator, class _Comp>
0037   _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> operator()(
0038       _Policy&& __policy,
0039       _ForwardIterator1 __first1,
0040       _ForwardIterator1 __last1,
0041       _ForwardIterator2 __first2,
0042       _ForwardIterator2 __last2,
0043       _ForwardOutIterator __result,
0044       _Comp __comp) const noexcept {
0045     if constexpr (__is_parallel_execution_policy_v<_RawExecutionPolicy> &&
0046                   __has_random_access_iterator_category_or_concept<_ForwardIterator1>::value &&
0047                   __has_random_access_iterator_category_or_concept<_ForwardIterator2>::value &&
0048                   __has_random_access_iterator_category_or_concept<_ForwardOutIterator>::value) {
0049       auto __res = __cpu_traits<_Backend>::__merge(
0050           __first1,
0051           __last1,
0052           __first2,
0053           __last2,
0054           __result,
0055           __comp,
0056           [&__policy](_ForwardIterator1 __g_first1,
0057                       _ForwardIterator1 __g_last1,
0058                       _ForwardIterator2 __g_first2,
0059                       _ForwardIterator2 __g_last2,
0060                       _ForwardOutIterator __g_result,
0061                       _Comp __g_comp) {
0062             using _MergeUnseq             = __pstl::__merge<_Backend, __remove_parallel_policy_t<_RawExecutionPolicy>>;
0063             [[maybe_unused]] auto __g_res = _MergeUnseq()(
0064                 std::__remove_parallel_policy(__policy),
0065                 std::move(__g_first1),
0066                 std::move(__g_last1),
0067                 std::move(__g_first2),
0068                 std::move(__g_last2),
0069                 std::move(__g_result),
0070                 std::move(__g_comp));
0071             _LIBCPP_ASSERT_INTERNAL(__g_res, "unsed/sed should never try to allocate!");
0072           });
0073       if (!__res)
0074         return nullopt;
0075       return __result + (__last1 - __first1) + (__last2 - __first2);
0076     } else {
0077       return std::merge(__first1, __last1, __first2, __last2, __result, __comp);
0078     }
0079   }
0080 };
0081
0082 } // namespace __pstl
0083 _LIBCPP_END_NAMESPACE_STD
0084
0085 #endif // _LIBCPP_STD_VER >= 17
0086
0087 _LIBCPP_POP_MACROS
0088
0089 #endif // _LIBCPP___PSTL_CPU_ALGOS_MERGE_H