0621fd0b88
Part of #102817. This patch optimizes `rng::generate_n` for segmented iterators by forwarding the implementation directly to `std::generate_n`. - before ``` rng::generate_n(deque<int>)/32 21.7 ns 22.0 ns 32000000 rng::generate_n(deque<int>)/50 30.8 ns 30.7 ns 22400000 rng::generate_n(deque<int>)/1024 492 ns 488 ns 1120000 rng::generate_n(deque<int>)/8192 3938 ns 3924 ns 179200 ``` - after ``` rng::generate_n(deque<int>)/32 11.0 ns 11.0 ns 64000000 rng::generate_n(deque<int>)/50 16.2 ns 16.1 ns 40727273 rng::generate_n(deque<int>)/1024 292 ns 286 ns 2240000 rng::generate_n(deque<int>)/8192 2291 ns 2302 ns 298667 ```
47 lines
1.5 KiB
C++
47 lines
1.5 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_GENERATE_N_H
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#define _LIBCPP___ALGORITHM_GENERATE_N_H
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#include <__algorithm/for_each_n.h>
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#include <__config>
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#include <__functional/identity.h>
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#include <__utility/forward.h>
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#include <__utility/move.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _OutputIterator, class _Size, class _Generator>
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
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__generate_n(_OutputIterator __first, _Size __orig_n, _Generator& __gen) {
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using __iter_ref = decltype(*__first);
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__identity __proj;
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auto __f = [&](__iter_ref __element) { std::forward<__iter_ref>(__element) = __gen(); };
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return std::__for_each_n(std::move(__first), __orig_n, __f, __proj);
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}
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template <class _OutputIterator, class _Size, class _Generator>
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
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generate_n(_OutputIterator __first, _Size __orig_n, _Generator __gen) {
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return std::__generate_n(std::move(__first), __orig_n, __gen);
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_GENERATE_N_H
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