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mordantemordante
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[libc++][format][1/3] Adds more benchmarks. (#101803)
This patch is the start of a series to improve the speed of std::format, std::format_to, std::format_to_n, and std::formatted_size. This is mostly achieved by changing the __output_buffer class. This new __output_buffer class also makes it easier to implement buffering for P3107R5 "Permit an efficient implementation of std::print"
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lines changed

5 files changed

+462
-2
lines changed

‎libcxx/test/benchmarks/CMakeLists.txt

+3
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@@ -147,6 +147,9 @@ set(BENCHMARK_TESTS
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deque_iterator.bench.cpp
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exception_ptr.bench.cpp
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filesystem.bench.cpp
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format/write_double_comparison.bench.cpp
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format/write_int_comparison.bench.cpp
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format/write_string_comparison.bench.cpp
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format_to_n.bench.cpp
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format_to.bench.cpp
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format.bench.cpp

‎libcxx/test/benchmarks/format.bench.cpp

+4-2
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@@ -20,8 +20,10 @@ static void BM_format_string(benchmark::State& state) {
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size_t size = state.range(0);
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std::basic_string<CharT> str(size, CharT('*'));
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while (state.KeepRunningBatch(str.size()))
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benchmark::DoNotOptimize(std::format(CSTR("{}"), str));
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while (state.KeepRunningBatch(str.size())) {
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std::basic_string<CharT> s = std::format(CSTR("{}"), str);
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benchmark::DoNotOptimize(s);
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}
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state.SetBytesProcessed(state.iterations() * size * sizeof(CharT));
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}

‎libcxx/test/benchmarks/format/write_double_comparison.bench.cpp

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@@ -0,0 +1,117 @@
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//===----------------------------------------------------------------------===//
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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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#include <array>
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#include <charconv>
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#include <cstdio>
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#include <format>
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#include <iterator>
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#include <list>
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#include <random>
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#include <vector>
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#include "benchmark/benchmark.h"
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std::array data = [] {
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std::uniform_real_distribution<double> distribution;
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std::mt19937 generator;
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std::array<double, 1000> result;
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std::generate_n(result.begin(), result.size(), [&] { return distribution(generator); });
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return result;
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}();
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static void BM_sprintf(benchmark::State& state) {
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std::array<char, 100> output;
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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sprintf(output.data(), "%f", value);
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benchmark::DoNotOptimize(output.data());
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}
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}
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static void BM_to_string(benchmark::State& state) {
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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std::string s = std::to_string(value);
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benchmark::DoNotOptimize(s);
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}
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}
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static void BM_to_chars(benchmark::State& state) {
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std::array<char, 100> output;
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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std::to_chars(output.data(), output.data() + output.size(), value);
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benchmark::DoNotOptimize(output.data());
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}
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}
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static void BM_to_chars_as_string(benchmark::State& state) {
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std::array<char, 100> output;
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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char* end = std::to_chars(output.data(), output.data() + output.size(), value).ptr;
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std::string s{output.data(), end};
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benchmark::DoNotOptimize(s);
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}
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}
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static void BM_format(benchmark::State& state) {
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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std::string s = std::format("{}", value);
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benchmark::DoNotOptimize(s);
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}
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}
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template <class C>
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static void BM_format_to_back_inserter(benchmark::State& state) {
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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C c;
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std::format_to(std::back_inserter(c), "{}", value);
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benchmark::DoNotOptimize(c);
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}
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}
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template <class F>
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static void BM_format_to_iterator(benchmark::State& state, F&& f) {
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auto output = f();
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while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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std::format_to(std::begin(output), "{}", value);
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benchmark::DoNotOptimize(std::begin(output));
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}
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}
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BENCHMARK(BM_sprintf);
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BENCHMARK(BM_to_string);
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BENCHMARK(BM_to_chars);
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BENCHMARK(BM_to_chars_as_string);
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BENCHMARK(BM_format);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::string);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::vector<char>);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::list<char>);
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::array>, ([] {
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std::array<char, 100> a;
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return a;
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}));
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::string>, ([] {
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std::string s;
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s.resize(100);
109+
return s;
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}));
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::vector>, ([] {
112+
std::vector<char> v;
113+
v.resize(100);
114+
return v;
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}));
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BENCHMARK_MAIN();

‎libcxx/test/benchmarks/format/write_int_comparison.bench.cpp

+117
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,117 @@
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//===----------------------------------------------------------------------===//
2+
//
3+
// 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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9+
#include <array>
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#include <charconv>
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#include <cstdio>
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#include <format>
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#include <iterator>
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#include <list>
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#include <random>
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#include <vector>
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#include "benchmark/benchmark.h"
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std::array data = [] {
21+
std::uniform_int_distribution<int> distribution{std::numeric_limits<int>::min(), std::numeric_limits<int>::max()};
22+
std::mt19937 generator;
23+
std::array<int, 1000> result;
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std::generate_n(result.begin(), result.size(), [&] { return distribution(generator); });
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return result;
26+
}();
27+
28+
static void BM_sprintf(benchmark::State& state) {
29+
std::array<char, 100> output;
30+
while (state.KeepRunningBatch(data.size()))
31+
for (auto value : data) {
32+
sprintf(output.data(), "%d", value);
33+
benchmark::DoNotOptimize(output.data());
34+
}
35+
}
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37+
static void BM_to_string(benchmark::State& state) {
38+
while (state.KeepRunningBatch(data.size()))
39+
for (auto value : data) {
40+
std::string s = std::to_string(value);
41+
benchmark::DoNotOptimize(s);
42+
}
43+
}
44+
45+
static void BM_to_chars(benchmark::State& state) {
46+
std::array<char, 100> output;
47+
48+
while (state.KeepRunningBatch(data.size()))
49+
for (auto value : data) {
50+
std::to_chars(output.data(), output.data() + output.size(), value);
51+
benchmark::DoNotOptimize(output.data());
52+
}
53+
}
54+
55+
static void BM_to_chars_as_string(benchmark::State& state) {
56+
std::array<char, 100> output;
57+
58+
while (state.KeepRunningBatch(data.size()))
59+
for (auto value : data) {
60+
char* end = std::to_chars(output.data(), output.data() + output.size(), value).ptr;
61+
std::string s{output.data(), end};
62+
benchmark::DoNotOptimize(s);
63+
}
64+
}
65+
66+
static void BM_format(benchmark::State& state) {
67+
while (state.KeepRunningBatch(data.size()))
68+
for (auto value : data) {
69+
std::string s = std::format("{}", value);
70+
benchmark::DoNotOptimize(s);
71+
}
72+
}
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74+
template <class C>
75+
static void BM_format_to_back_inserter(benchmark::State& state) {
76+
while (state.KeepRunningBatch(data.size()))
77+
for (auto value : data) {
78+
C c;
79+
std::format_to(std::back_inserter(c), "{}", value);
80+
benchmark::DoNotOptimize(c);
81+
}
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}
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84+
template <class F>
85+
static void BM_format_to_iterator(benchmark::State& state, F&& f) {
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auto output = f();
87+
while (state.KeepRunningBatch(data.size()))
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for (auto value : data) {
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std::format_to(std::begin(output), "{}", value);
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benchmark::DoNotOptimize(std::begin(output));
91+
}
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}
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BENCHMARK(BM_sprintf);
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BENCHMARK(BM_to_string);
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BENCHMARK(BM_to_chars);
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BENCHMARK(BM_to_chars_as_string);
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BENCHMARK(BM_format);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::string);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::vector<char>);
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BENCHMARK_TEMPLATE(BM_format_to_back_inserter, std::list<char>);
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::array>, ([] {
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std::array<char, 100> a;
104+
return a;
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}));
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::string>, ([] {
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std::string s;
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s.resize(100);
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return s;
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}));
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BENCHMARK_CAPTURE(BM_format_to_iterator, <std::vector>, ([] {
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std::vector<char> v;
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v.resize(100);
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return v;
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}));
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BENCHMARK_MAIN();

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