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  1. #include <algorithm>
  2. #include <chrono>
  3. #include <iostream>
  4. #include <iterator>
  5. #include <vector>
  6.  
  7. using clock_type = std::chrono::high_resolution_clock;
  8.  
  9. std::size_t test_cases = 100;
  10. std::vector<int> big_vector;
  11.  
  12.  
  13. void prepare_big_vector() {
  14.     for(int i = 0; i < 1 * 1000 * 1000; ++i)
  15.         big_vector.push_back(i % 1299653);
  16. }
  17.  
  18.  
  19. // Tests
  20.  
  21. clock_type::duration test_resize() {
  22.     clock_type::time_point start = clock_type::now();
  23.  
  24.     {
  25.         for(std::size_t i = 0; i < test_cases; ++i) {
  26.             std::vector<int> copied_vector;
  27.  
  28.             copied_vector.resize(big_vector.size());
  29.             std::copy(std::begin(big_vector), std::end(big_vector), std::begin(copied_vector));
  30.         }
  31.     }
  32.  
  33.     clock_type::time_point end = clock_type::now();
  34.     return end - start;
  35. }
  36.  
  37. clock_type::duration test_reserve() {
  38.     clock_type::time_point start = clock_type::now();
  39.  
  40.     {
  41.         for(std::size_t i = 0; i < test_cases; ++i) {
  42.             std::vector<int> copied_vector;
  43.  
  44.             copied_vector.reserve(big_vector.size());
  45.             std::copy(std::begin(big_vector), std::end(big_vector), std::begin(copied_vector));
  46.         }
  47.     }
  48.  
  49.     clock_type::time_point end = clock_type::now();
  50.     return end - start;
  51. }
  52.  
  53. clock_type::duration test_reserve2() {
  54.     clock_type::time_point start = clock_type::now();
  55.  
  56.     {
  57.         for(std::size_t i = 0; i < test_cases; ++i) {
  58.             std::vector<int> copied_vector;
  59.  
  60.             copied_vector.reserve(big_vector.size());
  61.             std::copy(std::begin(big_vector), std::end(big_vector), std::back_inserter(copied_vector));
  62.         }
  63.     }
  64.  
  65.     clock_type::time_point end = clock_type::now();
  66.     return end - start;
  67. }
  68.  
  69.  
  70. // Main
  71.  
  72. int main() {
  73.     prepare_big_vector();
  74.  
  75.     clock_type::duration resize_duration   = test_resize();
  76.     clock_type::duration reserve_duration  = test_reserve();
  77.     clock_type::duration reserve2_duration = test_reserve2();
  78.  
  79.     double resize_ms   = std::chrono::duration_cast<std::chrono::duration<double, std::milli>>(resize_duration).count();
  80.     double reserve_ms  = std::chrono::duration_cast<std::chrono::duration<double, std::milli>>(reserve_duration).count();
  81.     double reserve_ms2 = std::chrono::duration_cast<std::chrono::duration<double, std::milli>>(reserve2_duration).count();
  82.  
  83.     std::cout << "Resize [ms]: " << resize_ms  << std::endl;
  84.     std::cout << "Reserve [ms]: " << reserve_ms << std::endl;
  85.     std::cout << "Reserve (back_inserter) [ms]: " << reserve_ms2 << std::endl;
  86.  
  87.     system("pause");
  88.  
  89.     return 0;
  90. }
  91.  
Success #stdin #stdout #stderr 1.78s 3460KB
comments (?)
stdin 
Standard input is empty
stdout 
Resize [ms]: 571.282
Reserve [ms]: 509.561
Reserve (back_inserter) [ms]: 690.148
stderr 
sh: 1: pause: not found
https://ideone.com/sOL1Cx
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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