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