rand() was replaced by lrand48() because:
1. rand() seems to have different implementations on different platforms.
2. rand man pages explain it might have not-so-random LSBs, so it is not
goot to use it with % to randomize numbers to to limit.
Since lrand48() does not have default seed, ( like rand() has ) the
pseudo random generator of lrand48 is seeded with arbitrary seed in bdd_init().