Struct SplitMix64 

pub struct SplitMix64 { /* private fields */ }

SplitMix64 generator (Steele, Lea & Flood 2014).

A single-u64-state PRNG chosen for its tiny, portable, branch-free core: it produces a byte-identical stream for a given seed on every platform, which the equivalence harness relies on. That cross-platform guarantee covers next_u64 and next_f64, which are integer arithmetic plus one exact division by a power of two; it stops at standard_normal, whose Box–Muller transform routes through the platform math library — see that method’s portability note. The generator also caches the second Box–Muller variate, so standard_normal costs one transcendental pair per two draws.

Implementations

impl SplitMix64

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

Creates a generator seeded with seed.

Arguments

• seed — initial state; any u64 is valid (including 0).

pub const fn next_u64(&mut self) -> u64

Draws the next 64-bit value and advances the state.

Returns

A pseudo-random u64 uniformly distributed over the full range.

pub fn next_f64(&mut self) -> f64

Draws a uniform value in [0, 1) with 53 bits of resolution.

Returns

A pseudo-random f64 in the half-open unit interval.

pub fn standard_normal(&mut self) -> f64

Draws a standard-normal variate via Box–Muller, caching the spare.

The transform produces two independent N(0,1) variates per call; the second is cached and returned on the following call, halving the transcendental cost over a long stream.

Portability

The draw is deterministic: one seed gives one sequence, and the u64 stream underneath it is byte-identical on every target. The variate itself is not. Box–Muller evaluates ln, sin, and cos through the platform math library, which is accurate to well under an ulp but is not correctly rounded, so different targets — and even different optimisation levels on one target — can disagree in the last ulp or two. Compare standard-normal draws, and any statistic accumulated from them, with a tolerance; never bit-for-bit across builds or machines.

Returns

A pseudo-random f64 distributed as N(0, 1).

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 Debug for SplitMix64

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

Formats the value using the given formatter.