Struct SplitMix64 

pub struct SplitMix64 { /* private fields */ }

A tiny, fast, deterministic PRNG (Steele et al.’s SplitMix64).

This is not cryptographically secure, but it is excellent for jitter: it is allocation-free, const-constructible, has good statistical spread, and is perfectly reproducible from a seed. That reproducibility is the whole point in P2P/consensus testing.

Example

use sisyphus::{Jitter, SplitMix64};

let mut a = SplitMix64::new(42);
let mut b = SplitMix64::new(42);
// Same seed => identical stream => reproducible tests.
assert_eq!(a.next_unit_f64(), b.next_unit_f64());

Implementations

impl SplitMix64

pub const fn new(seed: u64) -> Self

Create a new generator from a 64-bit seed.

Examples found in repository

examples/jitter.rs (line 19)

fn delays_for_seed(seed: u64) -> Vec<Duration> {
    // ±50% symmetric jitter around an exponentially growing interval.
    let mut policy = ExponentialBackoff::new(Duration::from_millis(100), 2.0)
        .with_jitter(SplitMix64::new(seed), 0.5);
    (0..6).map(|_| policy.next_delay().unwrap()).collect()
}

pub fn next_u64(&mut self) -> u64

Advance the generator and return the next raw 64-bit value.

Trait Implementations

impl Clone for SplitMix64

fn clone(&self) -> SplitMix64

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for SplitMix64

impl Debug for SplitMix64

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

Formats the value using the given formatter.

impl Default for SplitMix64

fn default() -> Self

Returns the “default value” for a type.

impl Jitter for SplitMix64

fn next_unit_f64(&mut self) -> f64

Return the next pseudo-random value in the half-open range [0.0, 1.0).

fn apply(&mut self, base: Duration, factor: f64) -> Duration

Apply symmetric jitter of factor around base.