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| author | Connector Switch <c8ef@outlook.com> | 2025-10-20 19:37:33 +0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2025-10-20 19:37:33 +0800 |
| commit | 46e88169284aadb06fafcbe18ff440ff0fdebfa3 (patch) | |
| tree | 691488ba7506ab206395bb14e5cef5a7df2d374c /libcxx/include/__algorithm | |
| parent | 3027b4a55bf77b1ea10da718bd08a070555ead9a (diff) | |
| download | llvm-46e88169284aadb06fafcbe18ff440ff0fdebfa3.zip llvm-46e88169284aadb06fafcbe18ff440ff0fdebfa3.tar.gz llvm-46e88169284aadb06fafcbe18ff440ff0fdebfa3.tar.bz2 | |
[libcxx] Optimize std::generate for segmented iterators (#163006)
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>
Diffstat (limited to 'libcxx/include/__algorithm')
| -rw-r--r-- | libcxx/include/__algorithm/generate.h | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/libcxx/include/__algorithm/generate.h b/libcxx/include/__algorithm/generate.h index c95b527..c4cd75c 100644 --- a/libcxx/include/__algorithm/generate.h +++ b/libcxx/include/__algorithm/generate.h @@ -9,7 +9,9 @@ #ifndef _LIBCPP___ALGORITHM_GENERATE_H #define _LIBCPP___ALGORITHM_GENERATE_H +#include <__algorithm/for_each.h> #include <__config> +#include <__utility/forward.h> #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) # pragma GCC system_header @@ -20,8 +22,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD template <class _ForwardIterator, class _Generator> inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen) { - for (; __first != __last; ++__first) - *__first = __gen(); + using __iter_ref = decltype(*__first); + std::for_each(__first, __last, [&](__iter_ref __element) { std::forward<__iter_ref>(__element) = __gen(); }); } _LIBCPP_END_NAMESPACE_STD |