double t1, t2; t1 = (double)start_time.tv_sec+(double)start_time.tv_usec/1000000.0; t2 = (double)end_time.tv_sec+(double)end_time.tv_usec/1000000.0; return t2-t1;
return (end_time.tv_sec-start_time.tv_sec)+(double)(end_time.tv_usec-start_time.tv_usec)/1000000.00;
double time_diff(struct timeval start_time, struct timeval end_time){	double t1, t2;	t1 = (double)start_time.tv_sec+(double)start_time.tv_usec/1000000.0;	t2 = (double)end_time.tv_sec+(double)end_time.tv_usec/1000000.0;	return t2-t1;}