Just wanna estimate the process time of my algorithm homework.

Method 1

#include <sys/time.h>  

struct timeval t_start, t_end;  

gettimeofday(&t_start, NULL);  
double start = t_start.tv_sec + (double)t_start.tv_usec / 1000000;  

// Code to be estimated here  

gettimeofday(&t_end, NULL);  
double end = t_end.tv_sec + (double)t_end.tv_usec / 1000000;  

printf("%f seconds\n", end - start);  

This method came from one of my Data Structure homework in last semester.

Can estimated even if the process time is less than one second.

This is the method which I prefer to use.

But, sys/time.h is a POSIX header, not part of the C/C++ standard library.

So, this method can only be implemented on UNIX system.

Method 2

#include <time.h>  

clock_t start = clock();  

//Code to be estimated here  

clock_t end = clock();  

printf("%f seconds\n", (end - start) / (float)CLOCKS_PER_SEC);  

This method seems be common used.

But, seems it cannot estimate those process time less than one second.

Don't Know why... even if I remove the / (float)CLOCKS_PER_SEC. 

It still comes out zero. O_o"