[][src]Struct rand::rngs::SmallRng

pub struct SmallRng(_);

A small-state, fast non-crypto PRNG

SmallRng may be a good choice when a PRNG with small state, cheap initialization, good statistical quality and good performance are required. It is not a good choice when security against prediction or reproducibility are important.

This PRNG is feature-gated: to use, you must enable the crate feature small_rng.

The algorithm is deterministic but should not be considered reproducible due to dependence on platform and possible replacement in future library versions. For a reproducible generator, use a named PRNG from an external crate, e.g. rand_pcg or rand_chacha. Refer also to The Book.

The PRNG algorithm in SmallRng is chosen to be efficient on the current platform, without consideration for cryptography or security. The size of its state is much smaller than StdRng. The current algorithm is Pcg64Mcg on 64-bit platforms and Pcg32 on 32-bit platforms. Both are implemented by the rand_pcg crate.

Examples

Initializing SmallRng with a random seed can be done using SeedableRng::from_entropy:

use rand::{Rng, SeedableRng};
use rand::rngs::SmallRng;

// Create small, cheap to initialize and fast RNG with a random seed.
// The randomness is supplied by the operating system.
let mut small_rng = SmallRng::from_entropy();

When initializing a lot of SmallRng's, using thread_rng can be more efficient:

use std::iter;
use rand::{SeedableRng, thread_rng};
use rand::rngs::SmallRng;

// Create a big, expensive to initialize and slower, but unpredictable RNG.
// This is cached and done only once per thread.
let mut thread_rng = thread_rng();
// Create small, cheap to initialize and fast RNGs with random seeds.
// One can generally assume this won't fail.
let rngs: Vec<SmallRng> = iter::repeat(())
    .map(|()| SmallRng::from_rng(&mut thread_rng).unwrap())
    .take(10)
    .collect();

Trait Implementations

impl Clone for SmallRng[src]

fn clone_from(&mut self, source: &Self)1.0.0[src]

Performs copy-assignment from source. Read more

impl Debug for SmallRng[src]

impl RngCore for SmallRng[src]

impl SeedableRng for SmallRng[src]

type Seed = <Pcg64Mcg as SeedableRng>::Seed

Seed type, which is restricted to types mutably-dereferencable as u8 arrays (we recommend [u8; N] for some N). Read more

fn seed_from_u64(state: u64) -> Self[src]

Create a new PRNG using a u64 seed. Read more

fn from_entropy() -> Self[src]

Creates a new instance of the RNG seeded via [getrandom]. Read more

Auto Trait Implementations

impl Send for SmallRng

impl Unpin for SmallRng

impl Sync for SmallRng

impl UnwindSafe for SmallRng

impl RefUnwindSafe for SmallRng

Blanket Implementations

impl<R> Rng for R where
    R: RngCore + ?Sized
[src]

fn gen<T>(&mut self) -> T where
    Standard: Distribution<T>, 
[src]

Return a random value supporting the [Standard] distribution. Read more

fn gen_range<T: SampleUniform, B1, B2>(&mut self, low: B1, high: B2) -> T where
    B1: SampleBorrow<T> + Sized,
    B2: SampleBorrow<T> + Sized
[src]

Generate a random value in the range [low, high), i.e. inclusive of low and exclusive of high. Read more

fn sample<T, D: Distribution<T>>(&mut self, distr: D) -> T[src]

Sample a new value, using the given distribution. Read more

Important traits for DistIter<D, R, T>
fn sample_iter<T, D>(self, distr: D) -> DistIter<D, Self, T> where
    D: Distribution<T>,
    Self: Sized
[src]

Create an iterator that generates values using the given distribution. Read more

fn fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T)[src]

Fill dest entirely with random bytes (uniform value distribution), where dest is any type supporting AsByteSliceMut, namely slices and arrays over primitive integer types (i8, i16, u32, etc.). Read more

fn try_fill<T: AsByteSliceMut + ?Sized>(
    &mut self,
    dest: &mut T
) -> Result<(), Error>
[src]

Fill dest entirely with random bytes (uniform value distribution), where dest is any type supporting AsByteSliceMut, namely slices and arrays over primitive integer types (i8, i16, u32, etc.). Read more

fn gen_bool(&mut self, p: f64) -> bool[src]

Return a bool with a probability p of being true. Read more

fn gen_ratio(&mut self, numerator: u32, denominator: u32) -> bool[src]

Return a bool with a probability of numerator/denominator of being true. I.e. gen_ratio(2, 3) has chance of 2 in 3, or about 67%, of returning true. If numerator == denominator, then the returned value is guaranteed to be true. If numerator == 0, then the returned value is guaranteed to be false. Read more

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T> From<T> for T[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> FromCast<T> for T

impl<T, U> Cast<U> for T where
    U: FromCast<T>, 

impl<T, U> IntoBits<U> for T where
    U: FromBits<T>, 

impl<T> FromBits<T> for T

impl<V, T> VZip<V> for T where
    V: MultiLane<T>,