Module rand::distributions::weighted::alias_method

👎Deprecated since 0.8.0: moved to rand_distr crate

Struct rand::distributions::weighted::alias_method::WeightedIndex

pub struct WeightedIndex<W: Weight> { /* private fields */ }

👎Deprecated since 0.8.0: moved to rand_distr crate

Implementations

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impl<W: Weight> WeightedIndex<W>

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pub fn new(_weights: Vec<W>) -> Result<Self, WeightedError>

👎Deprecated since 0.8.0: moved to rand_distr crate

Trait Implementations

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impl<W: Debug + Weight> Debug for WeightedIndex<W>

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

Formats the value using the given formatter. Read more

Auto Trait Implementations

impl<W> RefUnwindSafe for WeightedIndex<W>where
W: RefUnwindSafe,

impl<W> Send for WeightedIndex<W>where
W: Send,

impl<W> Sync for WeightedIndex<W>where
W: Sync,

impl<W> Unpin for WeightedIndex<W>where
W: Unpin,

impl<W> UnwindSafe for WeightedIndex<W>where
W: UnwindSafe,

Blanket Implementations

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impl<T> Any for Twhere
T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more

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impl<T> Borrow<T> for Twhere
T: ?Sized,

const: unstable · source

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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impl<T> BorrowMut<T> for Twhere
T: ?Sized,

const: unstable · source

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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impl<T> From<T> for T

const: unstable · source

fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into for Twhere
U: From<T>,

const: unstable · source

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of +From<T> for U chooses to do.

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impl<T, U> TryFrom for Twhere
U: Into<T>,

type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

fn try_from(value: U) -> Result<T, <T as TryFrom>::Error>

Performs the conversion.

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impl<T, U> TryInto for Twhere
U: TryFrom<T>,

type Error = >::Error

The type returned in the event of a conversion error.

const: unstable · source

fn try_into(self) -> Result<U, >::Error>

Performs the conversion.

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impl<V, T> VZip<V> for Twhere
V: MultiLane<T>,

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fn vzip(self) -> V

Trait rand::distributions::weighted::alias_method::Weight

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pub trait Weight { }

👎Deprecated since 0.8.0: moved to rand_distr crate

Implementations on Foreign Types

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Implementors

Enum rand::distributions::weighted::WeightedError

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pub enum WeightedError {
+    NoItem,
+    InvalidWeight,
+    AllWeightsZero,
+    TooMany,
+}

Expand description

Error type returned from WeightedIndex::new.

Variants

`NoItem`

The provided weight collection contains no items.

`InvalidWeight`

A weight is either less than zero, greater than the supported maximum, +NaN, or otherwise invalid.

`AllWeightsZero`

All items in the provided weight collection are zero.

`TooMany`

Too many weights are provided (length greater than u32::MAX)

Trait Implementations

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impl Clone for WeightedError

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fn clone(&self) -> WeightedError

Returns a copy of the value. Read more

1.0.0 · source

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

Performs copy-assignment from source. Read more

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impl Debug for WeightedError

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

Formats the value using the given formatter. Read more

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impl Display for WeightedError

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

Formats the value using the given formatter. Read more

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impl Error for WeightedError

1.30.0 · source

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any. Read more

1.0.0 · source

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

1.0.0 · source

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

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fn provide(&'a self, demand: &mut Demand<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type based access to context intended for error reports. Read more

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impl PartialEq<WeightedError> for WeightedError

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

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

1.0.0 · source

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. Read more

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impl StructuralEq for WeightedError

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impl StructuralPartialEq for WeightedError

Auto Trait Implementations

impl RefUnwindSafe for WeightedError

impl UnwindSafe for WeightedError

Blanket Implementations

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impl<T> Any for Twhere
T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more

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impl<T> Borrow<T> for Twhere
T: ?Sized,

const: unstable · source

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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impl<T> BorrowMut<T> for Twhere
T: ?Sized,

const: unstable · source

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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impl<T> From<T> for T

const: unstable · source

fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into for Twhere
U: From<T>,

const: unstable · source

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of +From<T> for U chooses to do.

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impl<E> Provider for Ewhere
E: Error + ?Sized,

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fn provide(&'a self, demand: &mut Demand<'a>)

🔬This is a nightly-only experimental API. (provide_any)

Data providers should implement this method to provide all values they are able to +provide by using demand. Read more

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impl<T> ToOwned for Twhere
T: Clone,

type Owned = T

The resulting type after obtaining ownership.

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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more

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impl<T> ToString for Twhere
T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more

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impl<T, U> TryFrom for Twhere
U: Into<T>,

type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

fn try_from(value: U) -> Result<T, <T as TryFrom>::Error>

Performs the conversion.

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impl<T, U> TryInto for Twhere
U: TryFrom<T>,

type Error = >::Error

The type returned in the event of a conversion error.

const: unstable · source

fn try_into(self) -> Result<U, >::Error>

Performs the conversion.

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impl<V, T> VZip<V> for Twhere
V: MultiLane<T>,

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fn vzip(self) -> V

Module rand::distributions::weighted

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👎Deprecated since 0.8.0: use rand::distributions::{WeightedIndex, WeightedError} instead

Expand description

Weighted index sampling

This module is deprecated. Use crate::distributions::WeightedIndex and +crate::distributions::WeightedError instead.

Structs

WeightedIndex

A distribution using weighted sampling of discrete items

Enums

WeightedError

Error type returned from WeightedIndex::new.

Struct rand::distributions::weighted::WeightedIndex

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pub struct WeightedIndex<X: SampleUniform + PartialOrd> { /* private fields */ }

Expand description

A distribution using weighted sampling of discrete items

Sampling a WeightedIndex distribution returns the index of a randomly +selected element from the iterator used when the WeightedIndex was +created. The chance of a given element being picked is proportional to the +value of the element. The weights can use any type X for which an +implementation of Uniform<X> exists.

Performance

Time complexity of sampling from WeightedIndex is O(log N) where +N is the number of weights. As an alternative, +rand_distr::weighted_alias +supports O(1) sampling, but with much higher initialisation cost.

A WeightedIndex<X> contains a Vec<X> and a Uniform<X> and so its +size is the sum of the size of those objects, possibly plus some alignment.

Creating a WeightedIndex<X> will allocate enough space to hold N - 1 +weights of type X, where N is the number of weights. However, since +Vec doesn’t guarantee a particular growth strategy, additional memory +might be allocated but not used. Since the WeightedIndex object also +contains, this might cause additional allocations, though for primitive +types, Uniform<X> doesn’t allocate any memory.

Sampling from WeightedIndex will result in a single call to +Uniform<X>::sample (method of the Distribution trait), which typically +will request a single value from the underlying RngCore, though the +exact number depends on the implementation of Uniform<X>::sample.

Example

use rand::prelude::*;
+use rand::distributions::WeightedIndex;
+
+let choices = ['a', 'b', 'c'];
+let weights = [2,   1,   1];
+let dist = WeightedIndex::new(&weights).unwrap();
+let mut rng = thread_rng();
+for _ in 0..100 {
+    // 50% chance to print 'a', 25% chance to print 'b', 25% chance to print 'c'
+    println!("{}", choices[dist.sample(&mut rng)]);
+}
+
+let items = [('a', 0), ('b', 3), ('c', 7)];
+let dist2 = WeightedIndex::new(items.iter().map(|item| item.1)).unwrap();
+for _ in 0..100 {
+    // 0% chance to print 'a', 30% chance to print 'b', 70% chance to print 'c'
+    println!("{}", items[dist2.sample(&mut rng)].0);
+}

Implementations

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impl<X: SampleUniform + PartialOrd> WeightedIndex<X>

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pub fn new(weights: I) -> Result<WeightedIndex<X>, WeightedError>where
 I: IntoIterator,
 I::Item: SampleBorrow<X>,
 X: for<'a> AddAssign<&'a X> + Clone + Default,

Creates a new a WeightedIndex Distribution using the values +in weights. The weights can use any type X for which an +implementation of Uniform<X> exists.

Returns an error if the iterator is empty, if any weight is < 0, or +if its total value is 0.

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pub fn update_weights(
 &mut self,
 new_weights: &[(usize, &X)]
) -> Result<(), WeightedError>where
 X: for<'a> AddAssign<&'a X> + for<'a> SubAssign<&'a X> + Clone + Default,

Update a subset of weights, without changing the number of weights.

new_weights must be sorted by the index.

Using this method instead of new might be more efficient if only a small number of +weights is modified. No allocations are performed, unless the weight type X uses +allocation internally.

In case of error, self is not modified.