Struct rand::rngs::SmallRng

pub struct SmallRng(/* private fields */);

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. Note that depending on the application, StdRng may be faster on many modern platforms while providing higher-quality randomness. Furthermore, SmallRng is not a good choice when:

• Portability is required. Its implementation is not fixed. Use a named generator from an external crate instead, for example rand_xoshiro or rand_chacha. Refer also to The Book.
• Security against prediction is important. Use StdRng instead.

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

Implementations

impl SmallRng

pub fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error>

Construct an instance seeded from another Rng

We recommend that the source (master) RNG uses a different algorithm (i.e. is not SmallRng) to avoid correlations between the child PRNGs.

Example

let rng = SmallRng::from_rng(rand::thread_rng());

pub fn from_thread_rng() -> Self

Construct an instance seeded from the thread-local RNG

Panics

This method panics only if thread_rng fails to initialize.

pub fn seed_from_u64(state: u64) -> Self

Construct an instance from a u64 seed

This provides a convenient method of seeding a SmallRng from a simple number by use of another algorithm to mutate and expand the input. This is suitable for use with low Hamming Weight numbers like 0 and 1.

Warning: the implementation is deterministic but not portable: output values may differ according to platform and may be changed by a future version of the library.

Example

let rng = SmallRng::seed_from_u64(1);

Trait Implementations

impl Clone for SmallRng

fn clone(&self) -> SmallRng

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SmallRng

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

Formats the value using the given formatter.

impl PartialEq for SmallRng

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

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RngCore for SmallRng

fn next_u32(&mut self) -> u32

Return the next random u32.

fn next_u64(&mut self) -> u64

Return the next random u64.

fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data.

fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data.

fn read_adapter(&mut self) -> RngReadAdapter<'_, Self>

where Self: Sized,

Convert an RngCore to a RngReadAdapter.

impl Eq for SmallRng

impl StructuralPartialEq for SmallRng