double us_tdiff(struct timeval *end, struct timeval *start)
{
	return end->tv_sec * 1000000 + end->tv_usec - start->tv_sec * 1000000 - start->tv_usec;
}
double us_tdiff(struct timeval *end, struct timeval *start)
{
	return end->tv_sec * 1000000 + end->tv_usec - start->tv_sec * 1000000 - start->tv_usec;
}