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charconv_benchmark.cc
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charconv_benchmark.cc
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// Copyright 2018 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/strings/charconv.h"
#include <cstdlib>
#include <cstring>
#include <string>
#include "benchmark/benchmark.h"
namespace {
void BM_Strtod_Pi(benchmark::State& state) {
const char* pi = "3.14159";
for (auto s : state) {
benchmark::DoNotOptimize(pi);
benchmark::DoNotOptimize(strtod(pi, nullptr));
}
}
BENCHMARK(BM_Strtod_Pi);
void BM_Absl_Pi(benchmark::State& state) {
const char* pi = "3.14159";
const char* pi_end = pi + strlen(pi);
for (auto s : state) {
benchmark::DoNotOptimize(pi);
double v;
absl::from_chars(pi, pi_end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_Pi);
void BM_Strtod_Pi_float(benchmark::State& state) {
const char* pi = "3.14159";
for (auto s : state) {
benchmark::DoNotOptimize(pi);
benchmark::DoNotOptimize(strtof(pi, nullptr));
}
}
BENCHMARK(BM_Strtod_Pi_float);
void BM_Absl_Pi_float(benchmark::State& state) {
const char* pi = "3.14159";
const char* pi_end = pi + strlen(pi);
for (auto s : state) {
benchmark::DoNotOptimize(pi);
float v;
absl::from_chars(pi, pi_end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_Pi_float);
void BM_Strtod_HardLarge(benchmark::State& state) {
const char* num = "272104041512242479.e200";
for (auto s : state) {
benchmark::DoNotOptimize(num);
benchmark::DoNotOptimize(strtod(num, nullptr));
}
}
BENCHMARK(BM_Strtod_HardLarge);
void BM_Absl_HardLarge(benchmark::State& state) {
const char* numstr = "272104041512242479.e200";
const char* numstr_end = numstr + strlen(numstr);
for (auto s : state) {
benchmark::DoNotOptimize(numstr);
double v;
absl::from_chars(numstr, numstr_end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_HardLarge);
void BM_Strtod_HardSmall(benchmark::State& state) {
const char* num = "94080055902682397.e-242";
for (auto s : state) {
benchmark::DoNotOptimize(num);
benchmark::DoNotOptimize(strtod(num, nullptr));
}
}
BENCHMARK(BM_Strtod_HardSmall);
void BM_Absl_HardSmall(benchmark::State& state) {
const char* numstr = "94080055902682397.e-242";
const char* numstr_end = numstr + strlen(numstr);
for (auto s : state) {
benchmark::DoNotOptimize(numstr);
double v;
absl::from_chars(numstr, numstr_end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_HardSmall);
void BM_Strtod_HugeMantissa(benchmark::State& state) {
std::string huge(200, '3');
const char* num = huge.c_str();
for (auto s : state) {
benchmark::DoNotOptimize(num);
benchmark::DoNotOptimize(strtod(num, nullptr));
}
}
BENCHMARK(BM_Strtod_HugeMantissa);
void BM_Absl_HugeMantissa(benchmark::State& state) {
std::string huge(200, '3');
const char* num = huge.c_str();
const char* num_end = num + 200;
for (auto s : state) {
benchmark::DoNotOptimize(num);
double v;
absl::from_chars(num, num_end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_HugeMantissa);
std::string MakeHardCase(int length) {
// The number 1.1521...e-297 is exactly halfway between 12345 * 2**-1000 and
// the next larger representable number. The digits of this number are in
// the string below.
const std::string digits =
"1."
"152113937042223790993097181572444900347587985074226836242307364987727724"
"831384300183638649152607195040591791364113930628852279348613864894524591"
"272746490313676832900762939595690019745859128071117417798540258114233761"
"012939937017879509401007964861774960297319002612457273148497158989073482"
"171377406078223015359818300988676687994537274548940612510414856761641652"
"513434981938564294004070500716200446656421722229202383105446378511678258"
"370570631774499359748259931676320916632111681001853983492795053244971606"
"922718923011680846577744433974087653954904214152517799883551075537146316"
"168973685866425605046988661997658648354773076621610279716804960009043764"
"038392994055171112475093876476783502487512538082706095923790634572014823"
"78877699375152587890625" +
std::string(5000, '0');
// generate the hard cases on either side for the given length.
// Lengths between 3 and 1000 are reasonable.
return digits.substr(0, length) + "1e-297";
}
void BM_Strtod_Big_And_Difficult(benchmark::State& state) {
std::string testcase = MakeHardCase(state.range(0));
const char* begin = testcase.c_str();
for (auto s : state) {
benchmark::DoNotOptimize(begin);
benchmark::DoNotOptimize(strtod(begin, nullptr));
}
}
BENCHMARK(BM_Strtod_Big_And_Difficult)->Range(3, 5000);
void BM_Absl_Big_And_Difficult(benchmark::State& state) {
std::string testcase = MakeHardCase(state.range(0));
const char* begin = testcase.c_str();
const char* end = begin + testcase.size();
for (auto s : state) {
benchmark::DoNotOptimize(begin);
double v;
absl::from_chars(begin, end, v);
benchmark::DoNotOptimize(v);
}
}
BENCHMARK(BM_Absl_Big_And_Difficult)->Range(3, 5000);
} // namespace
// ------------------------------------------------------------------------
// Benchmark Time CPU Iterations
// ------------------------------------------------------------------------
// BM_Strtod_Pi 96 ns 96 ns 6337454
// BM_Absl_Pi 35 ns 35 ns 20031996
// BM_Strtod_Pi_float 91 ns 91 ns 7745851
// BM_Absl_Pi_float 35 ns 35 ns 20430298
// BM_Strtod_HardLarge 133 ns 133 ns 5288341
// BM_Absl_HardLarge 181 ns 181 ns 3855615
// BM_Strtod_HardSmall 279 ns 279 ns 2517243
// BM_Absl_HardSmall 287 ns 287 ns 2458744
// BM_Strtod_HugeMantissa 433 ns 433 ns 1604293
// BM_Absl_HugeMantissa 160 ns 160 ns 4403671
// BM_Strtod_Big_And_Difficult/3 236 ns 236 ns 2942496
// BM_Strtod_Big_And_Difficult/8 232 ns 232 ns 2983796
// BM_Strtod_Big_And_Difficult/64 437 ns 437 ns 1591951
// BM_Strtod_Big_And_Difficult/512 1738 ns 1738 ns 402519
// BM_Strtod_Big_And_Difficult/4096 3943 ns 3943 ns 176128
// BM_Strtod_Big_And_Difficult/5000 4397 ns 4397 ns 157878
// BM_Absl_Big_And_Difficult/3 39 ns 39 ns 17799583
// BM_Absl_Big_And_Difficult/8 43 ns 43 ns 16096859
// BM_Absl_Big_And_Difficult/64 550 ns 550 ns 1259717
// BM_Absl_Big_And_Difficult/512 4167 ns 4167 ns 171414
// BM_Absl_Big_And_Difficult/4096 9160 ns 9159 ns 76297
// BM_Absl_Big_And_Difficult/5000 9738 ns 9738 ns 70140