libcxx/test/benchmarks/numeric/gcd.bench.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14

#include <array>
#include <benchmark/benchmark.h>
#include <cstring>
#include <numeric>
#include <random>
#include "test_macros.h"

template <class T>
static std::array<T, 1000> generate(std::uniform_int_distribution<T> distribution = std::uniform_int_distribution<T>{
                                        std::numeric_limits<T>::min() + 1, std::numeric_limits<T>::max()}) {
  std::mt19937 generator;
  std::array<T, 1000> result;
  std::generate_n(result.begin(), result.size(), [&] { return distribution(generator); });
  return result;
}

static TEST_ALIGN_BENCHMARK void bm_gcd_random(benchmark::State& state) {
  std::array data = generate<int>();
  while (state.KeepRunningBatch(data.size() * data.size()))
    for (auto v0 : data)
      for (auto v1 : data)
        benchmark::DoNotOptimize(std::gcd(v0, v1));
}
BENCHMARK(bm_gcd_random)->Name("std::gcd() (random numbers)");

static TEST_ALIGN_BENCHMARK void bm_gcd_trivial(benchmark::State& state) {
  int lhs = ~static_cast<int>(0), rhs = 1;
  for (auto _ : state) {
    benchmark::DoNotOptimize(lhs);
    benchmark::DoNotOptimize(rhs);
    benchmark::DoNotOptimize(std::gcd(lhs, rhs));
  }
}
BENCHMARK(bm_gcd_trivial)->Name("std::gcd() (trivial inputs)");

static TEST_ALIGN_BENCHMARK void bm_gcd_complex(benchmark::State& state) {
  long long lhs = 2971215073;
  long long rhs = 1836311903;
  for (auto _ : state) {
    benchmark::DoNotOptimize(lhs);
    benchmark::DoNotOptimize(rhs);
    benchmark::DoNotOptimize(std::gcd(lhs, rhs));
  }
}
BENCHMARK(bm_gcd_complex)->Name("std::gcd() (adversarial inputs)");

BENCHMARK_MAIN();