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  1. #include <cstdlib>
  2. #include <vector>
  3.  
  4. #include <iostream>
  5. #include <string>
  6.  
  7. #include <chrono>
  8.  
  9. class TestTimer
  10. {
  11. public:
  12.     using clock = std::chrono::high_resolution_clock;
  13.     using time_point = clock::time_point;
  14.     using duration = clock::duration;
  15.     TestTimer(const std::string & name) : name(name),
  16.         start(clock::now())
  17.     {
  18.     }
  19.  
  20.     ~TestTimer()
  21.     {
  22.         time_point now(clock::now());
  23.         duration d = now - start;
  24.  
  25.         std::cout << name << " completed in " << d.count() * (double)duration::period::num / duration::period::den <<
  26.             " seconds" << std::endl;
  27.     }
  28.  
  29. private:
  30.     std::string name;
  31.     time_point start;
  32. };
  33.  
  34. struct Pixel
  35. {
  36.     Pixel()
  37.     {
  38.     }
  39.  
  40.     Pixel(unsigned char r, unsigned char g, unsigned char b) : r(r), g(g), b(b)
  41.     {
  42.     }
  43.  
  44.     unsigned char r, g, b;
  45. };
  46.  
  47. void UseVector()
  48. {
  49.     TestTimer t("UseVector");
  50.  
  51.     for(int i = 0; i < 1000; ++i)
  52.     {
  53.         int dimension = 999;
  54.  
  55.         std::vector<Pixel> pixels;
  56.         pixels.resize(dimension * dimension);
  57.  
  58.         for(int i = 0; i < dimension * dimension; ++i)
  59.         {
  60.             pixels[i].r = 255;
  61.             pixels[i].g = 0;
  62.             pixels[i].b = 0;
  63.         }
  64.     }
  65. }
  66.  
  67. void UseVectorPushBack()
  68. {
  69.     TestTimer t("UseVectorPushBack");
  70.  
  71.     for(int i = 0; i < 1000; ++i)
  72.     {
  73.         int dimension = 999;
  74.  
  75.         std::vector<Pixel> pixels;
  76.             pixels.reserve(dimension * dimension);
  77.  
  78.         for(int i = 0; i < dimension * dimension; ++i)
  79.             pixels.push_back(Pixel(255, 0, 0));
  80.     }
  81. }
  82.  
  83. void UseArray()
  84. {
  85.     TestTimer t("UseArray");
  86.  
  87.     for(int i = 0; i < 1000; ++i)
  88.     {
  89.         int dimension = 999;
  90.  
  91.         Pixel * pixels = (Pixel *)malloc(sizeof(Pixel) * dimension * dimension);
  92.  
  93.         for(int i = 0 ; i < dimension * dimension; ++i)
  94.         {
  95.             pixels[i].r = 255;
  96.             pixels[i].g = 0;
  97.             pixels[i].b = 0;
  98.         }
  99.  
  100.         free(pixels);
  101.     }
  102. }
  103.  
  104. int main()
  105. {
  106.     TestTimer t1("The whole thing");
  107.  
  108.     UseArray();
  109.     UseVector();
  110.     UseVectorPushBack();
  111.  
  112.     return 0;
  113. }
Success #stdin #stdout 3.87s 6544KB
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stdin
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Standard input is empty
stdout
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UseArray completed in 1.39487 seconds
UseVector completed in 1.37653 seconds
UseVectorPushBack completed in 1.12173 seconds
The whole thing completed in 3.89339 seconds
https://ideone.com/RLtDqK
language:
C++14 (gcc 8.3)
created:
10 days ago
visibility:
public

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