libcxx/benchmarks/to_chars.bench.cpp

   1 //===----------------------------------------------------------------------===//
   2 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   3 // See https://llvm.org/LICENSE.txt for license information.
   4 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   5 //
   6 //===----------------------------------------------------------------------===//
   7
   8 #include <array>
   9 #include <charconv>
  10 #include <random>
  11
  12 #include "benchmark/benchmark.h"
  13 #include "test_macros.h"
  14
  15 static const std::array<unsigned, 1000> input = [] {
  16   std::mt19937 generator;
  17   std::uniform_int_distribution<unsigned> distribution(0, std::numeric_limits<unsigned>::max());
  18   std::array<unsigned, 1000> result;
  19   std::generate_n(result.begin(), result.size(), [&] { return distribution(generator); });
  20   return result;
  21 }();
  22
  23 static void BM_to_chars_good(benchmark::State& state) {
  24   char buffer[128];
  25   int base = state.range(0);
  26   while (state.KeepRunningBatch(input.size()))
  27     for (auto value : input)
  28       benchmark::DoNotOptimize(std::to_chars(buffer, &buffer[128], value, base));
  29 }
  30 BENCHMARK(BM_to_chars_good)->DenseRange(2, 36, 1);
  31
  32 static void BM_to_chars_bad(benchmark::State& state) {
  33   char buffer[128];
  34   int base = state.range(0);
  35   struct sample {
  36     unsigned size;
  37     unsigned value;
  38   };
  39   std::array<sample, 1000> data;
  40   // Assume the failure occurs, on average, halfway during the conversion.
  41   std::transform(input.begin(), input.end(), data.begin(), [&](unsigned value) {
  42     std::to_chars_result result = std::to_chars(buffer, &buffer[128], value, base);
  43     return sample{unsigned((result.ptr - buffer) / 2), value};
  44   });
  45
  46   while (state.KeepRunningBatch(data.size()))
  47     for (auto element : data)
  48       benchmark::DoNotOptimize(std::to_chars(buffer, &buffer[element.size], element.value, base));
  49 }
  50 BENCHMARK(BM_to_chars_bad)->DenseRange(2, 36, 1);
  51
  52 int main(int argc, char** argv) {
  53   benchmark::Initialize(&argc, argv);
  54   if (benchmark::ReportUnrecognizedArguments(argc, argv))
  55     return 1;
  56
  57   benchmark::RunSpecifiedBenchmarks();
  58 }