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  1.  
  2. #include <chrono>
  3. #include <cstdlib>
  4. #include <functional>
  5. #include <iostream>
  6. #include <vector>
  7.  
  8. typedef unsigned long long Integer;
  9.  
  10. struct Functor
  11. {
  12.    void operator()(Integer i, Integer &sum) const
  13.    {
  14.       sum += std::rand();
  15.       if ( i > 0 )
  16.       {
  17.          this->operator()(i - 1, sum);
  18.       }
  19.    }
  20. };
  21.  
  22. void recurse(Integer i, Integer& sum)
  23. {
  24.    sum += std::rand();
  25.    if ( i > 0 )
  26.    {
  27.       recurse(i - 1, sum);
  28.    }
  29. }
  30.  
  31. int main()
  32. {
  33.    const Integer n(50ull * 1000ull * 1000ull);
  34.    const auto t_0(std::chrono::high_resolution_clock::now());
  35.    Integer functor_sum(0);
  36.    Functor functor;
  37.    functor(n, functor_sum);
  38.    const auto t_1(std::chrono::high_resolution_clock::now());
  39.    Integer sum(0);
  40.    recurse(n, sum);
  41.    const auto t_2(std::chrono::high_resolution_clock::now());
  42.    std::function<void(Integer, Integer&)> lambda_recurse([&lambda_recurse](Integer i, Integer& l_sum)
  43.    {
  44.       l_sum += std::rand();
  45.       if ( i > 0 )
  46.       {
  47.          lambda_recurse(i - 1, l_sum);
  48.       }
  49.    });
  50.    Integer lambda_sum(0);
  51.    lambda_recurse(n, lambda_sum);
  52.    const auto t_3(std::chrono::high_resolution_clock::now());
  53.    std::cout << "functor: " << std::chrono::duration_cast<std::chrono::milliseconds>(t_1 - t_0).count() << "\n";
  54.    std::cout << "plain: " << std::chrono::duration_cast<std::chrono::milliseconds>(t_2 - t_1).count() << "\n";
  55.    std::cout << "lambda: " << std::chrono::duration_cast<std::chrono::milliseconds>(t_3 - t_2).count() << "\n";
  56. }
Success #stdin #stdout 4.18s 3032KB
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stdin
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Standard input is empty
stdout
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functor: 1276
plain: 1233
lambda: 1674
https://ideone.com/4Y5Yym
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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