Struct spinoso_random::Mt

pub struct Mt { /* fields omitted */ }

The 32-bit Ruby flavor of the Mersenne Twister pseudorandom number generator.

The RNG is used to implement the Random class in Ruby Core. This RNG is a modified version of the MT19937 random number generator. It natively outputs u32.

Mt is not suitable for cryptographic use.

Size

Mt requires approximately 2.5KB of internal state.

You may wish to store an Mt on the heap in a Box to make it easier to embed in another struct.

Implementations

impl Mt

#[must_use]

pub fn with_seed(seed: u32) -> Self

Create a new Mersenne Twister random number generator using the given seed.

Examples

let seed = 123_456_789_u32;
let mut mt = Mt::with_seed(seed);
let rand = mt.next_int32();

#[must_use]

pub fn new_with_key<I>(key: I) -> Self where
    I: IntoIterator<Item = u32>,
    I::IntoIter: Clone, 

Create a new Mersenne Twister random number generator using the given key.

Key can have any length.

This function is used when initializing an Mt with more than 32 bits, such as when initializing with a Bignum seed.

MRI initializes the global SipHash seed with 4 u32s of entropy.

#[must_use]

pub fn next_int32(&mut self) -> u32

Generate next u32 output.

Generates a random number on (0..=0xffffffff)-interval.

u32 is the native output of the generator. This function advances the RNG step counter by one.

Examples

let mut mt = Mt::with_seed(5489);
assert_ne!(mt.next_int32(), mt.next_int32());

#[must_use]

pub fn next_real(&mut self) -> f64

Generate next f64 output.

Generates a random number on [0,1) with 53-bit resolution.

Examples

let mut mt = Mt::with_seed(5489);
assert_ne!(mt.next_real(), mt.next_real());

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

Fill a buffer with bytes generated from the RNG.

This method generates random u32s (the native output unit of the RNG) until dest is filled.

This method may discard some output bits if dest.len() is not a multiple of 4.

Examples

let mut mt = Mt::with_seed(5489);
let mut buf = [0; 32];
mt.fill_bytes(&mut buf);
assert_ne!([0; 32], buf);
let mut buf = [0; 31];
mt.fill_bytes(&mut buf);
assert_ne!([0; 31], buf);

pub fn reseed(&mut self, seed: u32)

Reseed a Mersenne Twister from a single u32.

Examples

let mut mt = Mt::with_seed(5489_u32);
let first = mt.next_int32();
mt.fill_bytes(&mut [0; 512]);
mt.reseed(5489_u32);
assert_eq!(first, mt.next_int32());

pub fn reseed_with_key<I>(&mut self, key: I) where
    I: IntoIterator<Item = u32>,
    I::IntoIter: Clone, 

Reseed a Mersenne Twister from an iterator of u32s.

Key can have any length.

Trait Implementations

impl Clone for Mt

fn clone(&self) -> Mt

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Mt

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

Formats the value using the given formatter.

impl Hash for Mt

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl Ord for Mt

fn cmp(&self, other: &Mt) -> Ordering

This method returns an Ordering between self and other.

#[must_use]

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl PartialEq<Mt> for Mt

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

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

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

This method tests for !=.

impl PartialOrd<Mt> for Mt

fn partial_cmp(&self, other: &Mt) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]

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

This method tests less than (for self and other) and is used by the < operator.

#[must_use]

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]

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

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl RngCore for Mt

#[must_use]

fn next_u64(&mut self) -> u64

Generate next u64 output.

This function is implemented by generating two u32s from the RNG and shifting + masking them into a u64 output.

Examples

let mut mt = Mt::with_seed(5489);
assert_ne!(mt.next_u64(), mt.next_u64());

#[must_use]

fn next_u32(&mut self) -> u32

Generate next u32 output.

u32 is the native output of the generator. This function advances the RNG step counter by one.

Examples

let mut mt = Mt::with_seed(5489);
assert_ne!(mt.next_u32(), mt.next_u32());

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

Fill a buffer with bytes generated from the RNG.

This method generates random u32s (the native output unit of the RNG) until dest is filled.

This method may discard some output bits if dest.len() is not a multiple of 4.

Examples

let mut mt = Mt::with_seed(5489);
let mut buf = [0; 32];
mt.fill_bytes(&mut buf);
assert_ne!([0; 32], buf);
let mut buf = [0; 31];
mt.fill_bytes(&mut buf);
assert_ne!([0; 31], buf);

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

Fill a buffer with bytes generated from the RNG.

This method generates random u32s (the native output unit of the RNG) until dest is filled.

This method may discard some output bits if dest.len() is not a multiple of 4.

try_fill_bytes is implemented with fill_bytes and is infallible.

Examples

let mut mt = Mt::with_seed(5489);
let mut buf = [0; 32];
mt.try_fill_bytes(&mut buf)?;
assert_ne!([0; 32], buf);
let mut buf = [0; 31];
mt.try_fill_bytes(&mut buf)?;
assert_ne!([0; 31], buf);

Errors

This method never returns an error. It is equivalent to calling the infallible fill_bytes method.

impl SeedableRng for Mt

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

Reseed from four u32s.

Examples

// Default MT seed
let seed = 5489_u128.to_le_bytes();
let mut mt = Mt::from_seed(seed);
assert_ne!(mt.next_u32(), mt.next_u32());

type Seed = [u8; 16]

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

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 Mt

impl StructuralEq for Mt

impl StructuralPartialEq for Mt