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  1. #include <chrono>
  2. #include <iostream>
  3. #include <vector>
  4.  
  5.  
  6. template <class T>
  7. inline void hash_combine(std::size_t& seed, T const& v)
  8. {
  9.     seed ^= std::hash<T>()(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
  10. }
  11.  
  12. namespace std
  13. {
  14. 	template<typename T>
  15. 	struct hash { };
  16.     template<typename T>
  17.     struct hash<std::vector<T>>
  18.     {
  19.         typedef std::vector<T> argument_type;
  20.         typedef std::size_t result_type;
  21.         result_type operator()(argument_type const& in) const
  22.         {
  23.             size_t size = in.size();
  24.             result_type seed = 0;
  25.             for (size_t i = 0; i < size; i++)
  26.                 //Combine the hash of the current vector with the hashes of the previous ones
  27.                 hash_combine(seed, in[i]);
  28.             return seed;
  29.         }
  30.     };
  31. }
  32.  
  33. int main() {
  34. 	std::vector<double> arr(1000*1000*10);
  35. 	auto start = std::chrono::high_resolution_clock::now();
  36. 	size_t hash = std::hash<std::vector<double>>()(arr);
  37. 	auto stop = std::chrono::high_resolution_clock::now();
  38. 	std::cout << "hash of " << arr.size() << " doubles took ";
  39. 	std::cout << std::chrono::duration_cast<std::chrono::microseconds>(stop - start).count();
  40. 	std::cout << " us and resulted in hash: " << hash << std::endl;
  41. 	return 0;
  42. }
Success #stdin #stdout 0.12s 3460KB
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hash of 10000000 doubles took 51306 us and resulted in hash: 990810500
https://ideone.com/tieHbd
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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