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

pub struct SmallRng(_);

An RNG recommended when small state, cheap initialization and good performance are required. 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 for StdRng.

Reproducibility of output from this generator is however not required, thus future library versions may use a different internal generator with different output. Further, this generator may not be portable and can produce different output depending on the architecture. If you require reproducible output, use a named RNG, for example XorShiftRng.

The current algorithm used on all platforms is Xorshift.

Examples

Initializing SmallRng with a random seed can be done using FromEntropy:

use rand::FromEntropy;
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
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fn clone_from(&mut self, source: &Self)
1.0.0
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Performs copy-assignment from source. Read more

impl Debug for SmallRng
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impl RngCore for SmallRng
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impl SeedableRng for SmallRng
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type Seed = <XorShiftRng 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
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Create a new PRNG using a u64 seed. Read more

Auto Trait Implementations

impl Send for SmallRng

impl Sync for SmallRng

Blanket Implementations

impl<R> Rng for R where
    R: RngCore + ?Sized
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fn gen<T>(&mut self) -> T where
    Standard: Distribution<T>, 
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Return a random value supporting the [Standard] distribution. Read more

fn gen_range<T: PartialOrd + SampleUniform>(&mut self, low: T, high: T) -> T
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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
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Sample a new value, using the given distribution. Read more

Important traits for DistIter<'a, D, R, T>
fn sample_iter<'a, T, D: Distribution<T>>(
    &'a mut self,
    distr: &'a D
) -> DistIter<'a, D, Self, T> where
    Self: Sized
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Create an iterator that generates values using the given distribution. Read more

fn fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T)
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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>
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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
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Return a bool with a probability p of being true. Read more

fn choose<'a, T>(&mut self, values: &'a [T]) -> Option<&'a T>
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Return a random element from values. Read more

fn choose_mut<'a, T>(&mut self, values: &'a mut [T]) -> Option<&'a mut T>
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Return a mutable pointer to a random element from values. Read more

fn shuffle<T>(&mut self, values: &mut [T])
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Shuffle a mutable slice in place. Read more

Important traits for Generator<T, R>
fn gen_iter<T>(&mut self) -> Generator<T, &mut Self> where
    Standard: Distribution<T>, 
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Deprecated since 0.5.0:

use Rng::sample_iter(&Standard) instead

Return an iterator that will yield an infinite number of randomly generated items. Read more

fn gen_weighted_bool(&mut self, n: u32) -> bool
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Deprecated since 0.5.0:

use gen_bool instead

Return a bool with a 1 in n chance of true Read more

Important traits for AsciiGenerator<R>
fn gen_ascii_chars(&mut self) -> AsciiGenerator<&mut Self>
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Deprecated since 0.5.0:

use sample_iter(&Alphanumeric) instead

Return an iterator of random characters from the set A-Z,a-z,0-9. Read more

impl<R> FromEntropy for R where
    R: SeedableRng
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impl<T> From for T
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impl<T, U> Into for T where
    U: From<T>, 
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impl<T> ToOwned for T where
    T: Clone
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type Owned = T

impl<T, U> TryFrom for T where
    T: From<U>, 
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type Error = !

🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
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impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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type Error = <U as TryFrom<T>>::Error

🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> BorrowMut for T where
    T: ?Sized
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impl<T> Any for T where
    T: 'static + ?Sized
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