Struct rand_pcg::Lcg64Xsh32

pub struct Lcg64Xsh32 { /* private fields */ }

A PCG random number generator (XSH RR 64/32 (LCG) variant).

Permuted Congruential Generator with 64-bit state, internal Linear Congruential Generator, and 32-bit output via “xorshift high (bits), random rotation” output function.

This is a 64-bit LCG with explicitly chosen stream with the PCG-XSH-RR output function. This combination is the standard pcg32.

Despite the name, this implementation uses 16 bytes (128 bit) space comprising 64 bits of state and 64 bits stream selector. These are both set by SeedableRng, using a 128-bit seed.

Note that two generators with different stream parameter may be closely correlated.

Implementations

impl Lcg64Xsh32

pub fn advance(&mut self, delta: u64)

Multi-step advance functions (jump-ahead, jump-back)

The method used here is based on Brown, “Random Number Generation with Arbitrary Stride,”, Transactions of the American Nuclear Society (Nov. 1994). The algorithm is very similar to fast exponentiation.

Even though delta is an unsigned integer, we can pass a signed integer to go backwards, it just goes “the long way round”.

Using this function is equivalent to calling next_32() delta number of times.

pub fn new(state: u64, stream: u64) -> Self

Construct an instance compatible with PCG seed and stream.

Note that two generators with different stream parameters may be closely correlated.

PCG specifies the following default values for both parameters:

• state = 0xcafef00dd15ea5e5
• stream = 0xa02bdbf7bb3c0a7

Trait Implementations

impl Clone for Lcg64Xsh32

fn clone(&self) -> Lcg64Xsh32

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Lcg64Xsh32

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

Formats the value using the given formatter.

impl PartialEq<Lcg64Xsh32> for Lcg64Xsh32

fn eq(&self, other: &Lcg64Xsh32) -> 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 Lcg64Xsh32

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.

impl SeedableRng for Lcg64Xsh32

We use a single 127-bit seed to initialise the state and select a stream. One seed bit (lowest bit of seed[8]) is ignored.

type Seed = [u8; 16]

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

fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed.

fn seed_from_u64(state: u64) -> Self

Create a new PRNG using a u64 seed.

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

Create a new PRNG seeded from another Rng.

fn from_entropy() -> Self

Creates a new instance of the RNG seeded via getrandom.

impl Eq for Lcg64Xsh32

impl StructuralEq for Lcg64Xsh32

impl StructuralPartialEq for Lcg64Xsh32