optional_speed.cpp

#include <chrono>
#include <iostream>
#include <string>

#include <boost/scoped_ptr.hpp>
#include <boost/optional.hpp>
#include <boost/utility/in_place_factory.hpp>

class Thing {
  int x;
public:
  __attribute__((noinline))
  Thing() : x(1) {}
};

void use_ptrs(int N) {
  for (int i = 0; i < N; ++i) {
    boost::scoped_ptr<Thing> p(new Thing);
  }
}

void use_optional(int N) {
  for (int i = 0; i < N; ++i) {
    boost::optional<Thing> o;
    o = boost::in_place();
  }
}

class Timer {
  std::string name;
  std::chrono::time_point<std::chrono::high_resolution_clock> t0;
public:
  Timer(const std::string& n) : name(n), t0(std::chrono::high_resolution_clock::now()) {}
  ~Timer() {
    std::chrono::milliseconds elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - t0);
    std::cout << name << " " << elapsed.count() << "ms" << std::endl;
  }
};

int main(void) {
  {
    Timer t("Pointers");
    use_ptrs(10 << 25);
  }
  {
    Timer t("Optional");
    use_optional(10 << 25);
  }
  return 0;
}

/*
 % make CXXFLAGS=-std=c++11 optional_speed && ./optional_speed
g++ -std=c++11    optional_speed.cpp   -o optional_speed
Pointers 9643ms
Optional 19500ms
*/