How to benchmark a C++ code

As the last step of software development you should test the performance of your code. This is a simple example how to benchmark the time consumption of different procedures in a C or C++ code. We will compare two procedures: calculating sinus and exponential values for 5e7 numbers. Let write a code with name test.cpp

#include
#define LIMIT 50000000
void exponential(){
double a;
for(int i=1;