Add 'third_party/abseil_cpp/' from commit '768eb2ca2857342673fcd462792ce04b8bac3fa3' r/781

git-subtree-dir: third_party/abseil_cpp
git-subtree-mainline: ffb2ae54beb5796cd408fbe15d2d2da09ff37adf
git-subtree-split: 768eb2ca2857342673fcd462792ce04b8bac3fa3

1 files changed, 204 insertions, 0 deletions

diff --git a/third_party/abseil_cpp/absl/strings/charconv_benchmark.cc b/third_party/abseil_cpp/absl/strings/charconv_benchmark.cc
new file mode 100644
index 000000000000..e8c7371d6586
--- /dev/null
+++ b/third_party/abseil_cpp/absl/strings/charconv_benchmark.cc
@@ -0,0 +1,204 @@
+// 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