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  1.  
  2. #pragma once
  3.  
  4. #include <chrono>
  5. #include <type_traits>
  6.  
  7. template <typename Clock>
  8. class stopwatch
  9. {
  10. public:
  11. 	typedef Clock clock;
  12. 	typedef typename clock::time_point time_point;
  13. 	typedef typename clock::duration duration;
  14.  
  15. private:
  16. 	time_point last_;
  17.  
  18. public:
  19. 	stopwatch()
  20. 		: last_(clock::now())
  21. 	{}
  22.  
  23. 	void reset()
  24. 	{
  25. 		*this = stopwatch();
  26. 	}
  27.  
  28. 	time_point now() const
  29. 	{
  30. 		return clock::now();
  31. 	}
  32.  
  33. 	duration elapsed() const
  34. 	{
  35. 		return now() - last_;
  36. 	}
  37.  
  38. 	duration tick()
  39. 	{
  40. 		time_point dummy;
  41. 		return tick(dummy);
  42. 	}
  43.  
  44. 	duration tick(time_point& now_)
  45. 	{
  46. 		now_ = now();
  47. 		auto elapsed = now_ - last_;
  48. 		last_ = now_;
  49. 		return elapsed;
  50. 	}
  51. };
  52.  
  53. typedef stopwatch<std::chrono::steady_clock> default_stopwatch;
  54.  
  55. template <typename T, typename Rep, typename Period, 
  56. 	typename = typename std::enable_if<std::is_floating_point<T>::value>::type>
  57. T float_cast(const std::chrono::duration<Rep, Period>& duration, T mul = T(1))
  58. {
  59. 	return duration.count() * mul * (T(Period::num) / T(Period::den));
  60. }
  61.  
  62.  
  63. #include <cstring>
  64. #include <algorithm>
  65. #include <array>
  66. #include <functional>
  67. #include <iostream>
  68. #include <random>
  69.  
  70. template <typename RNG>
  71. RNG make_rng()
  72. {
  73. 	std::random_device rd;
  74. 	std::array<typename RNG::result_type, RNG::state_size> seed_data;
  75. 	std::generate(seed_data.begin(), seed_data.end(), std::ref(rd));
  76. 	std::seed_seq seq(seed_data.begin(), seed_data.end());
  77. 	return RNG(seq);
  78. }
  79.  
  80. template <typename RNG>
  81. void test_rng(RNG& rng, void* buffer, std::size_t size)
  82. {
  83. 	while (size >= sizeof(decltype(rng())))
  84. 	{
  85. 		auto r = rng();
  86. 		std::memcpy(buffer, &r, sizeof r);
  87. 		buffer = static_cast<char*>(buffer) + sizeof r;
  88. 		size -= sizeof r;
  89. 	}
  90. }
  91.  
  92. int main()
  93. {
  94. 	const std::size_t mb = 512;
  95. 	std::vector<char> buf(mb * 1024 * 1024);
  96. 	default_stopwatch sw;
  97. 	double t;
  98. 	auto rng1 = make_rng<std::mt19937>();
  99. 	auto rng2 = make_rng<std::mt19937_64>();
  100. 	auto rng3 = std::minstd_rand((std::random_device()()));
  101.  
  102. 	sw.reset();
  103. 	test_rng(rng1, buf.data(), buf.size());
  104. 	t = float_cast<double>(sw.elapsed());
  105. 	std::cout << "mt19937: " << t << " - " << mb / t << " MB/s\n";
  106.  
  107. 	sw.reset();
  108. 	test_rng(rng2, buf.data(), buf.size());
  109. 	t = float_cast<double>(sw.elapsed());
  110. 	std::cout << "mt19937_64: " << t << " - " << mb / t << " MB/s\n";
  111.  
  112. 	sw.reset();
  113. 	test_rng(rng3, buf.data(), buf.size());
  114. 	t = float_cast<double>(sw.elapsed());
  115. 	std::cout << "minstd_rand: " << t << " - " << mb / t << " MB/s\n";
  116. }
Success #stdin #stdout 4.38s 3276KB
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mt19937: 1.43599 - 356.548 MB/s
mt19937_64: 1.50422 - 340.377 MB/s
minstd_rand: 0.858734 - 596.227 MB/s
https://ideone.com/ui7upc
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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