There are different ways to seed many RNGs (for parallel RNGs).
Below summarizes 3 popular ways.
Seeding RNGs using
std::collections::hash_map::RandomState
or rand::thread_rng
is preferred.
Seed Using System Time
use std::time::{SystemTime, UNIX_EPOCH};
use rand::SmallRng;
fn main () {
let seed = SystemTime::now()
.duration_since(UNIX_EPOCH)
.unwrap()
.as_nanos()
& ((1 << 65) - 1);
let mut rng = SmallRng::seed_from_u64(seed);
}
Seed Using std::collections::hash_map::RandomState
std::collections::hash_map::RandomState gets true (or close to true) random bytes using entropy
as the base random state
which is cached using thread-local storage.
Subsequent instantiations increment the random state to ensure different states.
use std::collections::hash_map::RandomState;
use std::hash::{BuildHasher, Hasher};
use rand::SmallRng;
fn main() {
let seed = RandomState::new().build_hasher().finish();
let mut rng = Xoshiro256PlusPlus::seed_from_u64(seed);
}
Seed Using a Master RNG
use rand::{SmallRng, thread_rng};
fn main() {
let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
}