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  1. #include <iostream>
  2. #include <cstdlib>
  3. #include <iostream>
  4. #include <chrono>
  5. #include <vector>
  6. class C{
  7. 	public: float hello;  
  8.     public: float hello2s[10];  
  9.     public: C(){
  10.         hello=((double) rand() / (RAND_MAX))*10;
  11.         for(int n=0;n<10;n++){
  12.         	hello2s[n]= ((double) rand() / (RAND_MAX))*10;
  13.         }
  14.     }
  15.     public: float calculateCheap(){
  16.         return hello;
  17.     }
  18.     public: float calculateExpensive(){
  19.     	float result=1;
  20.     	result=hello2s[0]*hello2s[1]*hello2s[2]*hello2s[3]*hello2s[4];
  21.         return result;
  22.     }
  23. };
  24. int main(){
  25.     const int numTest=10000;
  26.     C  d[numTest];
  27.     C* e[numTest];
  28.     for(int n=0;n<numTest;n++){
  29.         d[n]=C();
  30.         e[n]=new C();
  31.     }
  32.     float accu=0;
  33.     auto t1= std::chrono::system_clock::now();
  34.     for(int n=0;n<numTest;n++){
  35.         accu+=d[n].calculateExpensive();  //direct call
  36.     }
  37.     auto t2= std::chrono::system_clock::now();
  38.     for(int n=0;n<numTest;n++){
  39.         accu+=e[n]->calculateCheap();     //indirect call
  40.     }
  41.     auto t3= std::chrono::system_clock::now();
  42.     std::cout<<"direct call time ="<<(t2-t1).count()<<std::endl;
  43.     std::cout<<"indirect call time ="<<(t3-t2).count()<<std::endl;
  44.     std::cout<<"print to disable compiler cheat="<<accu<<std::endl;
  45. }
  46.  
Success #stdin #stdout 0s 16440KB
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stdin
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Standard input is empty
stdout
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direct call time =21637
indirect call time =23236
print to disable compiler cheat=3.17658e+07
https://ideone.com/IJwmQ6
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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