Compute the executing time in the code

struct timeval tv , tv2 ;
unsigned long      start_utime , end_utime;
float      time_period;
...
...

...
gettimeofday(&tv,NULL);
start_utime = tv.tv_sec * 1000000 + tv.tv_usec;

....
....
....

gettimeofday(&tv2,NULL);
end_utime = tv2.tv_sec * 1000000 + tv2.tv_usec;
time_period = ((float)(end_utime - start_utime)) /1000000;