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  1. #include <cstdlib>
  2. #include <cstring>
  3. #include <ctime>
  4. #include <algorithm>
  5. #include <iostream>
  6. #include <vector>
  7.  
  8. class stopwatch
  9. {
  10. 	clock_t last_;
  11. public:
  12. 	stopwatch()
  13. 	{
  14. 		reset();
  15. 	}
  16. 	void reset()
  17. 	{
  18. 		last_ = std::clock();
  19. 	}
  20. 	double time()
  21. 	{
  22. 		return (std::clock() - last_) / static_cast<double>(CLOCKS_PER_SEC);
  23. 	}
  24. };
  25.  
  26. void my_copy(void* dst, const void* src, std::size_t size)
  27. {
  28.   std::size_t pack_size = size / sizeof(long long);
  29.   std::size_t leftover_size = size - pack_size * sizeof(long long);
  30.  
  31.   while (pack_size--)
  32. 		*(long long*)dst = *(long long*)src;
  33.  
  34.   while (leftover_size--)
  35. 		*(char*)dst = *(char*)src;
  36. }
  37.  
  38. int main()
  39. {
  40. 	std::vector<char> source(52428800), destination(52428800);
  41. 	std::generate(source.begin(), source.end(), rand);
  42.  
  43. 	{
  44. 		stopwatch w;
  45. 		for (int i = 10; i--; )
  46. 			std::copy(source.begin(), source.end(), destination.begin());
  47. 		std::cout << "copy time: " << w.time() << '\n';
  48. 	}
  49.  
  50. 	{
  51. 		stopwatch w;
  52. 		for (int i = 10; i--; )
  53. 			std::memcpy(destination.data(), source.data(), source.size());
  54. 		std::cout << "memcpy time: " << w.time() << '\n';
  55. 	}
  56.  
  57. 	{
  58. 		stopwatch w;
  59. 		for (int i = 10; i--; )
  60. 			my_copy(destination.data(), source.data(), source.size());
  61. 		std::cout << "my_copy time: " << w.time() << '\n';
  62. 	}
  63. }
Success #stdin #stdout 2.08s 2828KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
copy time: 0.25
memcpy time: 0.25
my_copy time: 0.19
https://ideone.com/GEdPp
language:
C++14 (gcc 8.3)
created:
14 years ago
visibility:
public

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