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  1. // Example program
  2. #include <iostream>
  3. #include <string>
  4. #include <cstdlib> //for random
  5. #include <cmath>  //for pow
  6. #include <chrono>
  7.  
  8. int main()
  9. {
  10.     size_t seed=rand(); //The testbench will be different everytime, but the testbench will be the same for both paths.
  11.     static const size_t NUM_ITERS=3000000;
  12.     std::chrono::time_point<std::chrono::system_clock> start1, end1,start2,end2;
  13.     uint32_t finhash;
  14.  
  15.     //Pow
  16.     srand(seed);
  17.     finhash=0;
  18.     start1 = std::chrono::system_clock::now();
  19.     for(size_t i=0;i<NUM_ITERS;i++)
  20.     {
  21.         uint32_t n=rand() & 0x1F;
  22.         finhash^=(uint32_t)pow(2,n);   
  23.     }
  24.     end1 = std::chrono::system_clock::now();
  25.     std::chrono::duration<double> elapsed_seconds1 = end1-start1;
  26.     std::cout << "Pow elapsed time: " << elapsed_seconds1.count() << "s.  Hash was " << finhash << std::endl;
  27.  
  28.     //leftshift
  29.     srand(seed);
  30.     finhash=0;
  31.     start2 = std::chrono::system_clock::now();
  32.     for(size_t i=0;i<NUM_ITERS;i++)
  33.     {
  34.         uint32_t n=rand() & 0x1F;
  35.         finhash^=(uint32_t)(1 << n);   
  36.     }
  37.     end2 = std::chrono::system_clock::now();
  38.     std::chrono::duration<double> elapsed_seconds2 = end2-start2;
  39.     std::cout << "LeftShift elapsed time: " << elapsed_seconds2.count() << "s.  Hash was " << finhash << std::endl;
  40.  
  41.     return 0;
  42. }
Success #stdin #stdout 0.37s 3456KB
comments ()
stdin 
Standard input is empty
stdout 
Pow elapsed time: 0.301115s.  Hash was 1193342845
LeftShift elapsed time: 0.0688188s.  Hash was 1193342845
https://ideone.com/0vlQNK
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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