optimize append - #2164
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optimize append#2164
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optimize loop
Contributor
|
Thanks for the PR. Could you post a benchmark demonstrating the effect of this change in the comments here? |
Contributor
|
I've performed the following elementary benchmark: gcc (g++-10 (Homebrew GCC 10.2.0_4) 10.2.0): here's the benchmark code: #include <benchmark/benchmark.h>
#include <fmt/format.h>
#include <fmt/printf.h>
void one_format_argument(benchmark::State& state) {
const auto format_string = "{}" + std::string(state.range(0), 'x');
const auto test_output = fmt::format(format_string, 'a');
if (test_output != "a" + std::string(state.range(0), 'x')) {
throw std::runtime_error("wrong");
}
for (auto _ : state) {
benchmark::DoNotOptimize(fmt::format(format_string, 'a', 'a'));
}
}
void five_format_arguments(benchmark::State& state) {
auto format_string = std::string();
for (int i = 0; i < 5; ++i) {
format_string += "{}" + std::string(state.range(0), 'x');
}
const auto test_output = fmt::format(format_string, 'a', 'a', 'a', 'a', 'a');
if (state.range(0) == 0 && test_output != std::string(5, 'a')) {
throw std::runtime_error("wrong");
}
for (auto _ : state) {
benchmark::DoNotOptimize(
fmt::format(format_string, 'a', 'a', 'a', 'a', 'a'));
}
}
void ten_format_arguments(benchmark::State& state) {
auto format_string = std::string();
for (int i = 0; i < 10; ++i) {
format_string += "{}" + std::string(state.range(0), 'x');
}
const auto test_output = fmt::format(format_string, 'a', 'a', 'a', 'a', 'a',
'a', 'a', 'a', 'a', 'a');
if (state.range(0) == 0 && test_output != std::string(10, 'a')) {
throw std::runtime_error("wrong");
}
for (auto _ : state) {
benchmark::DoNotOptimize(fmt::format(format_string, 'a', 'a', 'a', 'a', 'a',
'a', 'a', 'a', 'a', 'a'));
}
}
BENCHMARK(one_format_argument)->Arg(0)->Arg(10)->Arg(100)->Arg(1000);
BENCHMARK(five_format_arguments)->Arg(0)->Arg(10)->Arg(100)->Arg(1000);
BENCHMARK(ten_format_arguments)->Arg(0)->Arg(10)->Arg(100)->Arg(1000);
BENCHMARK_MAIN(); |
Contributor
|
Thank you both! |
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Avoid one unneeded empty loop pass, e.g. with
std::string message = fmt::sprintf("The answer is %d", 42);(mostly if % placeholder is at the beginning or end of the string to be formatted)
I agree that my contributions are licensed under the {fmt} license, and agree to future changes to the licensing.