Struct SimRng 

pub struct SimRng { /* private fields */ }

The sim’s random stream: xoshiro256** holding four words of state.

Insert one as a resource and every draw the sim makes is reproducible from the state it holds. Copy, so a system can take a snapshot of the stream (record its state_words) as cheaply as a value read.

Do not build a series of seeds out of arithmetic: seeded(s) and seeded(s + GAMMA), or any small multiple of GAMMA, expand to states that share three of four words, and correlated streams follow. Derive a stream per system or entity from WorldSeed instead; it mixes the tag before expanding.

Implementations

impl SimRng

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

A stream seeded by seed through SplitMix64.

Any seed is valid, including 0. Two runs of the same seed produce the same stream on every target.

pub const fn from_words(words: [u64; 4]) -> Self

A stream from four raw state words, for a save that stores the words itself instead of the serialised resource.

All-zero words would make xoshiro emit zeros forever, so that one input is remapped to 0’s seeded stream rather than left as a trap.

pub const fn state_words(&self) -> [u64; 4]

The four state words: the whole stream position, for a save.

from_words(state_words()) resumes exactly where the stream stood.

Trait Implementations

impl Clone for SimRng

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Component for SimRng

where Self: Send + Sync + 'static,

const STORAGE_TYPE: StorageType = bevy_ecs::component::StorageType::SparseSet

A constant indicating the storage type used for this component.

type Mutability = Mutable

A marker type to assist Bevy with determining if this component is mutable, or immutable. Mutable components will have Component<Mutability = Mutable>, while immutable components will instead have Component<Mutability = Immutable>.

fn register_required_components( _requiree: ComponentId, required_components: &mut RequiredComponentsRegistrator<'_, '_>, )

Registers required components.

fn clone_behavior() -> ComponentCloneBehavior

Called when registering this component, allowing to override clone function (or disable cloning altogether) for this component.

fn relationship_accessor() -> Option<ComponentRelationshipAccessor<Self>>

Returns ComponentRelationshipAccessor required for working with relationships in dynamic contexts.

fn on_add() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_add ComponentHook for this Component if one is defined.

fn on_insert() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_insert ComponentHook for this Component if one is defined.

fn on_discard() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_discard ComponentHook for this Component if one is defined.

fn on_remove() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_remove ComponentHook for this Component if one is defined.

fn on_despawn() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_despawn ComponentHook for this Component if one is defined.

fn map_entities<E>(_this: &mut Self, _mapper: &mut E)

where E: EntityMapper,

Maps the entities on this component using the given EntityMapper. This is used to remap entities in contexts like scenes and entity cloning. When deriving Component, this is populated by annotating fields containing entities with #[entities]

const HAS_SUMMARY_TICK: bool = false

Set this constant to true if the component should track a summary tick.

impl Copy for SimRng

impl Debug for SimRng

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for SimRng

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for SimRng

impl PartialEq for SimRng

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

Equality operator ==.

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

Inequality operator !=.

impl Resource for SimRng

where Self: Send + Sync + 'static,

impl Rng for SimRng

fn next_u64(&mut self) -> u64

The next 64 bits: multiply, rotate, multiply, then the state update.

fn next_u32(&mut self) -> u32

The next 32 bits, taken from the top half of a draw: the low bits of an xoshiro word carry more linear structure than the high ones.

fn random<T: Sample>(&mut self) -> T

A value of T, uniform over its whole domain.

fn random_range<R: SampleRange>(&mut self, range: R) -> R::Output

A value uniform in range, e.g. random_range(0..enemies.len()), random_range(0.0..TAU), random_range(-8..=8).

fn bool(&mut self) -> bool

One bit, exactly half the time, from the top bit of a draw.

fn random_bool(&mut self, p: f64) -> bool

True with probability p, clamped to 0..=1: p <= 0 never, p >= 1 always. Panics on NaN.

fn unit_f32(&mut self) -> f32

Uniform in 0..1, built from the top 24 bits of one draw.

fn unit_f64(&mut self) -> f64

Uniform in 0..1, built from the top 53 bits of one draw.

fn below(&mut self, bound: u32) -> u32

Uniform in 0..bound, 0 for bound == 0 (which consumes no draw).

fn below_u64(&mut self, bound: u64) -> u64

below for a 64-bit bound, e.g. an index into a huge table or a hit roll over a wide damage range.

fn pick_index(&mut self, len: usize) -> Option<usize>

A uniform index in 0..len, or None when len == 0.

fn pick<'a, T>(&mut self, items: &'a [T]) -> Option<&'a T>

A uniform element of items, or None when it is empty.

fn weighted_index(&mut self, weights: &[f32]) -> Option<usize>

An index in 0..weights.len() with probability proportional to its weight, or None when no weight is positive.

fn shuffle<T>(&mut self, items: &mut [T])

Fisher-Yates, backwards: for i from len - 1 down to 1, swap i with below(i + 1) (so an element may stay put).

impl Serialize for SimRng

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for SimRng