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Use lower_bound instead of find_if to lookup time_zones. #5548

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Merged
merged 8 commits into from
May 28, 2025
Merged

Use lower_bound instead of find_if to lookup time_zones. #5548

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fad780a
Use `lower_bound` instead of `find_if` to lookup `time_zone`s.
YexuanXiao May 27, 2025
48c0d88
Remove the extra asterisk and add the benchmark to CMakeLists.txt
YexuanXiao May 27, 2025
3347fa1
Make the references point to const objects
YexuanXiao May 27, 2025
f27f49f
Use range-for.
StephanTLavavej May 28, 2025
fccce41
Use `const auto&`, avoid quasi-shadowing `tzdb`.
StephanTLavavej May 28, 2025
8cdf08e
Conditional operator => if-statement.
StephanTLavavej May 28, 2025
a0a7371
De Morgan isn't just a good idea - it's the law.
StephanTLavavej May 28, 2025
5a55610
Comment and test the sorted guarantee.
StephanTLavavej May 28, 2025
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1 change: 1 addition & 0 deletions benchmarks/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,7 @@ add_benchmark(has_single_bit src/has_single_bit.cpp)
add_benchmark(iota src/iota.cpp)
add_benchmark(is_sorted_until src/is_sorted_until.cpp)
add_benchmark(locale_classic src/locale_classic.cpp)
add_benchmark(locate_zone src/locate_zone.cpp)
add_benchmark(minmax_element src/minmax_element.cpp)
add_benchmark(mismatch src/mismatch.cpp)
add_benchmark(move_only_function src/move_only_function.cpp)
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19 changes: 19 additions & 0 deletions benchmarks/src/locate_zone.cpp
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@@ -0,0 +1,19 @@
// Copyright (c) Microsoft Corporation.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "benchmark/benchmark.h"
#include <chrono>

void locate_zone(benchmark::State& state) {
auto&& tzdb = std::chrono::get_tzdb();
for (auto _ : state) {
for (std::size_t i = 0; i != tzdb.zones.size(); ++i) {
auto res = tzdb.locate_zone(tzdb.zones[i].name());
benchmark::DoNotOptimize(res);
}
}
}

BENCHMARK(locate_zone);

BENCHMARK_MAIN();
5 changes: 3 additions & 2 deletions stl/inc/chrono
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Expand Up @@ -2105,8 +2105,9 @@ namespace chrono {

template <class _Ty>
_NODISCARD const _Ty* _Locate_zone_impl(const vector<_Ty>& _Vec, string_view _Name) {
const auto _Result = _STD find_if(_Vec.begin(), _Vec.end(), [&](auto& _Tz) { return _Tz.name() == _Name; });
return _Result == _Vec.end() ? nullptr : &*_Result;
const auto _Result = _STD lower_bound(
_Vec.begin(), _Vec.end(), _Name, [](const auto& _Tz, const auto& _Sv) { return _Tz.name() < _Sv; });
return (_Result == _Vec.end() || _Result->name() != _Name) ? nullptr : &*_Result;
}

_EXPORT_STD struct tzdb {
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