ofRandom_vs_myRandom.h

#include <iostream>
#include <random>
#include <chrono>
#include <functional>
#include <string>
using namespace std;

std::mt19937 random_engine;
std::uniform_real_distribution<float> random_distribution;

float of_random(float max) {
  // copied from ofRandom()
  return (max * rand() / RAND_MAX) * (1.0f - std::numeric_limits<float>::epsilon());
}

float my_random(float max) {
  return random_distribution(random_engine) * max;
}

namespace FastRandom
{
  static unsigned long xorshf96(void) {
    static unsigned long x = 123456789, y = 362436069, z = 521288629;
    unsigned long t;

    x ^= x << 16;
    x ^= x >> 5;
    x ^= x << 1;

    t = x;
    x = y;
    y = z;

    z = t ^ x ^ y;
    return z;
  }

  static inline unsigned long random(void) {
    return xorshf96();
  }

  static inline float randomf(void) {
    return (float)random() / (float)std::numeric_limits<unsigned long>::max();
  }
};

double my_stopwatch(const std::string label, std::function<void()> f) {
  cout << " ---- " << endl;
  cout << "[ " << label << " ]" << endl;
  auto start = chrono::steady_clock::now();
  f();
  auto end = chrono::steady_clock::now();
  auto record = chrono::duration<double, micro>(end - start).count();
  cout << "record:" << record * 0.001 << " ms." << endl;
  return record;
}


int main(int argc, char *argv[]) {
  const int num_loop = 50000;
  random_distribution.param(std::uniform_real_distribution<float>::param_type(0.0, 1.0));
  random_engine.seed(std::random_device()());

  {
    const auto record = my_stopwatch("ofRandom", [=]() {
      for (int i = 0; i < num_loop; i++) {
        auto r = of_random(3.0f);
      }
    });
    cout << "average:" << record / num_loop << " micro seconds." << endl;
  }

  {
    const auto record = my_stopwatch("my_random", [=]() {
      for (int i = 0; i < num_loop; i++) {
        auto r = my_random(3.0f);
      }
    });
    cout << "average:" << record / num_loop << " micro seconds." << endl;
  }

  {
    const auto record = my_stopwatch("FastRandom::randomf", [=]() {
      for (int i = 0; i < num_loop; i++) {
        auto r = FastRandom::randomf() * 3.0f;
      }
    });
    cout << "average:" << record / num_loop << " micro seconds." << endl;
  }

  return 0;
}

ElCapitan OF0.9.7 結果だいたいこんな感じ

[ ofRandom ]
record:0.297501 ms.
average:0.00595002 micro seconds.

[ my_random ]
record:1.72936 ms.
average:0.0345872 micro seconds.

[ FastRandom::randomf ]
record:0.763401 ms.
average:0.015268 micro seconds.

Windows 10 OF0.9.7での結果

[ ofRandom ]
record:3.94065 ms.
average:0.078813 micro seconds.

[ my_random ]
record:5.50069 ms.
average:0.110014 micro seconds.

[ FastRandom::randomf ]
record:0.844018 ms.
average:0.0168804 micro seconds.