46e8816928
Part of #102817. This patch attempts to optimize the performance of `std::generate` for segmented iterators. Below are the benchmark numbers from `libcxx\test\benchmarks\algorithms\modifying\generate.bench.cpp`. Test cases that use segmented iterators have also been added. - before ``` std::generate(deque<int>)/32 194 ns 193 ns 3733333 std::generate(deque<int>)/50 276 ns 276 ns 2488889 std::generate(deque<int>)/1024 5096 ns 5022 ns 112000 std::generate(deque<int>)/8192 40806 ns 40806 ns 17231 ``` - after ``` std::generate(deque<int>)/32 106 ns 105 ns 6400000 std::generate(deque<int>)/50 139 ns 138 ns 4977778 std::generate(deque<int>)/1024 2713 ns 2699 ns 248889 std::generate(deque<int>)/8192 18983 ns 19252 ns 37333 ``` --------- Co-authored-by: A. Jiang <de34@live.cn>
32 lines
1.0 KiB
C++
32 lines
1.0 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_H
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#define _LIBCPP___ALGORITHM_GENERATE_H
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#include <__algorithm/for_each.h>
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#include <__config>
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#include <__utility/forward.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_BEGIN_NAMESPACE_STD
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template <class _ForwardIterator, class _Generator>
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
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generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen) {
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using __iter_ref = decltype(*__first);
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std::for_each(__first, __last, [&](__iter_ref __element) { std::forward<__iter_ref>(__element) = __gen(); });
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ALGORITHM_GENERATE_H
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