branch-prediction-test.cpp

#include <chrono>
#include <iostream>
#include <numeric>

int main() {
  using namespace std;
  using namespace std::chrono;
  constexpr auto reps = numeric_limits<unsigned>::max() >> 1;

  {
    auto x = 1, counter = 0;
    auto start = high_resolution_clock::now();    
    for (unsigned i = 0u; i < reps; ++i) {
      if (x == 1)
	      ++counter;
      x = (x << 0) % 3;
    }
    auto end = high_resolution_clock::now();
    std::cout << counter << "\t" << duration_cast<milliseconds>(end - start).count() << "ms\n";
  }

  {
    auto x = 1, counter = 0;
    auto start = high_resolution_clock::now();
    for (unsigned i = 0u; i < reps; ++i) {
      if (x == 1)
	      ++counter;
      x = (x << 1) % 3;
    }
    auto end = high_resolution_clock::now();
    std::cout << counter << "\t" << duration_cast<milliseconds>(end - start).count() << "ms\n";
  }

  return 0;
}