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  1. #include <iostream>
  2. #include <vector>
  3. #include <cstdlib>
  4. #include <chrono>
  5.  
  6. using namespace std;
  7.  
  8. #define MAXN 100000000
  9.  
  10. class timer
  11. {
  12.   using T = std::chrono::time_point<std::chrono::steady_clock>;
  13.   T t1, t2;
  14. public:
  15.   void start() { t1 = std::chrono::steady_clock::now(); }
  16.   void stop() { t2 = std::chrono::steady_clock::now(); }
  17.   void print(const char *title) const { std::cout << title << (t2 - t1).count() << endl; }
  18. };
  19.  
  20. int main()
  21. {
  22.   vector <unsigned> v(MAXN);
  23.   unsigned s;
  24.   timer t;
  25.  
  26.   srand(time(0));
  27.  
  28.   s = 0;
  29.   for (unsigned q=0; q<MAXN; ++q) v[q] = rand();
  30.   t.start();
  31.   for (unsigned q=0, n=v.size(); q<n; ++q) s += v[q];
  32.   t.stop();
  33.   cout << s << endl;
  34.   t.print("Index: ");
  35.  
  36.   s = 0;
  37.   for (unsigned q=0; q<MAXN; ++q) v[q] = rand();
  38.   t.start();
  39.   for (auto x : v) s += x;
  40.   t.stop();
  41.   cout << s << endl;
  42.   t.print("Byval: ");
  43.  
  44.   s = 0;
  45.   for (unsigned q=0; q<MAXN; ++q) v[q] = rand();
  46.   t.start();
  47.   for (auto &x : v) s += x;
  48.   t.stop();
  49.   cout << s << endl;
  50.   t.print("Byref: ");
  51.  
  52.   return 0;
  53. }
Success #stdin #stdout 2.4s 15240KB
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stdin
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Standard input is empty
stdout
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3852871726
Index: 41888244
1275459847
Byval: 42361756
2080980504
Byref: 43436973
https://ideone.com/KN8W1k
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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