How to calculate the execution time in C?

Question

How can I calculate the execution time in the following code:

#include   /* Core input/output operations                         */
#include 

        

Answer 1

I'd try the following :

int     timeval_subtract ( struct timeval *result, struct timeval *x, struct timeval *y ) {

    if ( x->tv_usec < y->tv_usec ) {
            int nsec = ( y->tv_usec - x->tv_usec ) / 1000000 + 1;
            y->tv_usec -= 1000000 * nsec;
            y->tv_sec += nsec;
    }
    if (x->tv_usec - y->tv_usec > 1000000) {
            int nsec = ( x->tv_usec - y->tv_usec ) / 1000000;
            y->tv_usec += 1000000 * nsec;
            y->tv_sec -= nsec;
    }

    result->tv_sec = x->tv_sec - y->tv_sec;
    result->tv_usec = x->tv_usec - y->tv_usec;

    return x->tv_sec < y->tv_sec;
}

void Start ( struct timeval *timer_profiling ) {
        if ( timer_profiling == NULL )   return;
        gettimeofday ( timer_profiling , NULL );
        return;
}

void End ( struct timeval *timer_profiling , char *msg ) {
        struct timeval res;
        struct timeval now;
        gettimeofday ( &now , NULL );

        if ( msg == NULL )      return;

        timeval_subtract ( &res , &now , timer_profiling );
        sprintf ( msg , "[ %ld,%.3ld ms]" , res.tv_sec*1000 + (long)round(res.tv_usec/1000) , res.tv_usec - (long)round(res.tv_usec/1000)*1000);

        return;
}

Start(&s) one with an allocated timer_profiling , then retrieve the result in a string by calling End(&s,buff);