Struct `SmallRng`

struct SmallRng(_)

A small-state, fast, non-crypto, non-portable PRNG

This is the "standard small" RNG, a generator with the following properties:

Non-portable: any future library version may replace the algorithm and results may be platform-dependent. (For a small portable generator, use the rand_pcg or rand_xoshiro crate.)
Non-cryptographic: output is easy to predict (insecure)
Quality: statistically good quality
Fast: the RNG is fast for both bulk generation and single values, with consistent cost of method calls
Fast initialization
Small state: little memory usage (current state size is 16-32 bytes depending on platform)

The current algorithm is Xoshiro256PlusPlus on 64-bit platforms and Xoshiro128PlusPlus on 32-bit platforms. Both are also implemented by the rand_xoshiro crate.

Seeding (construction)

This generator implements the SeedableRng trait. All methods are suitable for seeding, but note that, even with a fixed seed, output is not portable. Some suggestions:

To automatically seed with a unique seed, use [SeedableRng::from_rng]:

use rand::SeedableRng;
use rand::rngs::SmallRng;
let rng = SmallRng::from_rng(&mut rand::rng());
# let _: SmallRng = rng;

or [SeedableRng::from_os_rng]:

# use rand::SeedableRng;
# use rand::rngs::SmallRng;
let rng = SmallRng::from_os_rng();
# let _: SmallRng = rng;

To use a deterministic integral seed, use seed_from_u64. This uses a hash function internally to yield a (typically) good seed from any input.
```
# use rand::{SeedableRng, rngs::SmallRng};
let rng = SmallRng::seed_from_u64(1);
# let _: SmallRng = rng;
```
To seed deterministically from text or other input, use rand_seeder.

Generation

The generators implements RngCore and thus also [Rng][crate::Rng]. See also the Random Values chapter in the book.

Implementations

`impl Clone for SmallRng`

fn clone(self: &Self) -> SmallRng

`impl Debug for SmallRng`

fn fmt(self: &Self, f: &mut Formatter<'_>) -> Result

`impl Eq for SmallRng`

`impl Freeze for SmallRng`

`impl PartialEq for SmallRng`

fn eq(self: &Self, other: &SmallRng) -> bool

`impl RefUnwindSafe for SmallRng`

`impl RngCore for SmallRng`

fn next_u32(self: &mut Self) -> u32
fn next_u64(self: &mut Self) -> u64
fn fill_bytes(self: &mut Self, dest: &mut [u8])

`impl SeedableRng for SmallRng`

fn from_seed(seed: <Self as >::Seed) -> Self
fn seed_from_u64(state: u64) -> Self

`impl Send for SmallRng`

`impl StructuralPartialEq for SmallRng`

`impl Sync for SmallRng`

`impl Unpin for SmallRng`

`impl UnsafeUnpin for SmallRng`

`impl UnwindSafe for SmallRng`

`impl<R> Rng for SmallRng`

`impl<R> TryRngCore for SmallRng`

fn try_next_u32(self: &mut Self) -> Result<u32, <R as TryRngCore>::Error>
fn try_next_u64(self: &mut Self) -> Result<u64, <R as TryRngCore>::Error>
fn try_fill_bytes(self: &mut Self, dst: &mut [u8]) -> Result<(), <R as TryRngCore>::Error>

`impl<T> Any for SmallRng`

fn type_id(self: &Self) -> TypeId

`impl<T> Borrow for SmallRng`

fn borrow(self: &Self) -> &T

`impl<T> BorrowMut for SmallRng`

fn borrow_mut(self: &mut Self) -> &mut T

`impl<T> CloneToUninit for SmallRng`

unsafe fn clone_to_uninit(self: &Self, dest: *mut u8)

`impl<T> From for SmallRng`

fn from(t: T) -> T: Returns the argument unchanged.

`impl<T> ToOwned for SmallRng`

fn to_owned(self: &Self) -> T
fn clone_into(self: &Self, target: &mut T)

`impl<T, U> Into for SmallRng`

fn into(self: Self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of [From]<T> for U chooses to do.

`impl<T, U> TryFrom for SmallRng`

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

`impl<T, U> TryInto for SmallRng`

fn try_into(self: Self) -> Result<U, <U as TryFrom<T>>::Error>

`impl<V, T> VZip for SmallRng`

fn vzip(self: Self) -> V