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  1. #include <iostream>
  2. #include <unordered_map>
  3. #include <cmath>
  4. #include <chrono>
  5. #include <functional>
  6.  
  7. class TimedSection {
  8. public:
  9. 	TimedSection(std::string nameOfMeasurment) : nameOfMeasurment(nameOfMeasurment) {
  10. 		start = std::chrono::high_resolution_clock::now();
  11. 	}
  12.  
  13. 	~TimedSection() {
  14. 		auto elapsedTime = std::chrono::high_resolution_clock::now() - start;
  15. 		std::cout << "Measurment taken(" << nameOfMeasurment << ") Elapsed time: " <<
  16. 			std::chrono::duration_cast<std::chrono::nanoseconds>(elapsedTime).count() << "ns" << std::endl;
  17. 	}
  18.  
  19. private:
  20. 	std::string nameOfMeasurment;
  21. 	std::chrono::time_point<std::chrono::high_resolution_clock> start;
  22. };
  23.  
  24. template<typename Arg, typename F>
  25. auto memoize(F&& f) {
  26. 	return [f](Arg arg) {
  27. 		static std::unordered_map<Arg, decltype(f(arg))> memoizedArgs;
  28. 		if(memoizedArgs.find(arg) == memoizedArgs.end()) {
  29. 			memoizedArgs[arg] = f(arg);
  30. 		}
  31.  
  32. 		return memoizedArgs[arg];
  33. 	};
  34. }
  35.  
  36. int main() {
  37. 	std::function<int(int)> fib = [&fib](int n) {return n < 2 ? 1 : fib(n-1) + fib(n-2);};
  38.  
  39.  
  40. 	auto memoizedFib = memoize<int>(fib);
  41.  
  42. 	{
  43. 		TimedSection("without memoization");
  44. 		for(auto i = 0; i < 100; i++) {
  45. 			fib(30);
  46. 		}
  47. 	}
  48.  
  49. 	{
  50. 		TimedSection("with memoization");
  51. 		for(auto i = 0; i < 100; i++) {
  52. 			memoizedFib(30);
  53. 		}
  54. 	}
  55.  
  56. 	return 0;
  57. }
Success #stdin #stdout 2.47s 3276KB
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Standard input is empty
stdout
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Measurment taken(without memoization) Elapsed time: 602ns
Measurment taken(with memoization) Elapsed time: 272ns
https://ideone.com/pxX5As
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
secret

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