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| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| </span><span class="doccomment">//! Weighted index sampling |
| |
| </span><span class="kw">use </span><span class="kw">crate</span>::distributions::uniform::{SampleBorrow, SampleUniform, UniformSampler}; |
| <span class="kw">use </span><span class="kw">crate</span>::distributions::Distribution; |
| <span class="kw">use </span><span class="kw">crate</span>::Rng; |
| <span class="kw">use </span>core::cmp::PartialOrd; |
| <span class="kw">use </span>core::fmt; |
| |
| <span class="comment">// Note that this whole module is only imported if feature="alloc" is enabled. |
| </span><span class="kw">use </span>alloc::vec::Vec; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"serde1"</span>)] |
| </span><span class="kw">use </span>serde::{Serialize, Deserialize}; |
| |
| <span class="doccomment">/// 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`](https://docs.rs/rand_distr/*/rand_distr/weighted_alias/index.html) |
| /// 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); |
| /// } |
| /// ``` |
| /// |
| /// [`Uniform<X>`]: crate::distributions::Uniform |
| /// [`RngCore`]: crate::RngCore |
| </span><span class="attribute">#[derive(Debug, Clone, PartialEq)] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, derive(Serialize, Deserialize))] |
| #[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"alloc"</span>)))] |
| </span><span class="kw">pub struct </span>WeightedIndex<X: SampleUniform + PartialOrd> { |
| cumulative_weights: Vec<X>, |
| total_weight: X, |
| weight_distribution: X::Sampler, |
| } |
| |
| <span class="kw">impl</span><X: SampleUniform + PartialOrd> WeightedIndex<X> { |
| <span class="doccomment">/// 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. |
| /// |
| /// [`Uniform<X>`]: crate::distributions::uniform::Uniform |
| </span><span class="kw">pub fn </span>new<I>(weights: I) -> <span class="prelude-ty">Result</span><WeightedIndex<X>, WeightedError> |
| <span class="kw">where |
| </span>I: IntoIterator, |
| I::Item: SampleBorrow<X>, |
| X: <span class="kw">for</span><<span class="lifetime">'a</span>> ::core::ops::AddAssign<<span class="kw-2">&</span><span class="lifetime">'a </span>X> + Clone + Default, |
| { |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = weights.into_iter(); |
| <span class="kw">let </span><span class="kw-2">mut </span>total_weight: X = iter.next().ok_or(WeightedError::NoItem)<span class="question-mark">?</span>.borrow().clone(); |
| |
| <span class="kw">let </span>zero = <X <span class="kw">as </span>Default>::default(); |
| <span class="kw">if </span>!(total_weight >= zero) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>weights = Vec::<X>::with_capacity(iter.size_hint().<span class="number">0</span>); |
| <span class="kw">for </span>w <span class="kw">in </span>iter { |
| <span class="comment">// Note that `!(w >= x)` is not equivalent to `w < x` for partially |
| // ordered types due to NaNs which are equal to nothing. |
| </span><span class="kw">if </span>!(w.borrow() >= <span class="kw-2">&</span>zero) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight); |
| } |
| weights.push(total_weight.clone()); |
| total_weight += w.borrow(); |
| } |
| |
| <span class="kw">if </span>total_weight == zero { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::AllWeightsZero); |
| } |
| <span class="kw">let </span>distr = X::Sampler::new(zero, total_weight.clone()); |
| |
| <span class="prelude-val">Ok</span>(WeightedIndex { |
| cumulative_weights: weights, |
| total_weight, |
| weight_distribution: distr, |
| }) |
| } |
| |
| <span class="doccomment">/// 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. |
| </span><span class="kw">pub fn </span>update_weights(<span class="kw-2">&mut </span><span class="self">self</span>, new_weights: <span class="kw-2">&</span>[(usize, <span class="kw-2">&</span>X)]) -> <span class="prelude-ty">Result</span><(), WeightedError> |
| <span class="kw">where </span>X: <span class="kw">for</span><<span class="lifetime">'a</span>> ::core::ops::AddAssign<<span class="kw-2">&</span><span class="lifetime">'a </span>X> |
| + <span class="kw">for</span><<span class="lifetime">'a</span>> ::core::ops::SubAssign<<span class="kw-2">&</span><span class="lifetime">'a </span>X> |
| + Clone |
| + Default { |
| <span class="kw">if </span>new_weights.is_empty() { |
| <span class="kw">return </span><span class="prelude-val">Ok</span>(()); |
| } |
| |
| <span class="kw">let </span>zero = <X <span class="kw">as </span>Default>::default(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>total_weight = <span class="self">self</span>.total_weight.clone(); |
| |
| <span class="comment">// Check for errors first, so we don't modify `self` in case something |
| // goes wrong. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>prev_i = <span class="prelude-val">None</span>; |
| <span class="kw">for </span><span class="kw-2">&</span>(i, w) <span class="kw">in </span>new_weights { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(old_i) = prev_i { |
| <span class="kw">if </span>old_i >= i { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight); |
| } |
| } |
| <span class="kw">if </span>!(<span class="kw-2">*</span>w >= zero) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight); |
| } |
| <span class="kw">if </span>i > <span class="self">self</span>.cumulative_weights.len() { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::TooMany); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>old_w = <span class="kw">if </span>i < <span class="self">self</span>.cumulative_weights.len() { |
| <span class="self">self</span>.cumulative_weights[i].clone() |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.total_weight.clone() |
| }; |
| <span class="kw">if </span>i > <span class="number">0 </span>{ |
| old_w -= <span class="kw-2">&</span><span class="self">self</span>.cumulative_weights[i - <span class="number">1</span>]; |
| } |
| |
| total_weight -= <span class="kw-2">&</span>old_w; |
| total_weight += w; |
| prev_i = <span class="prelude-val">Some</span>(i); |
| } |
| <span class="kw">if </span>total_weight <= zero { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::AllWeightsZero); |
| } |
| |
| <span class="comment">// Update the weights. Because we checked all the preconditions in the |
| // previous loop, this should never panic. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>iter = new_weights.iter(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>prev_weight = zero.clone(); |
| <span class="kw">let </span><span class="kw-2">mut </span>next_new_weight = iter.next(); |
| <span class="kw">let </span><span class="kw-2">&</span>(first_new_index, <span class="kw">_</span>) = next_new_weight.unwrap(); |
| <span class="kw">let </span><span class="kw-2">mut </span>cumulative_weight = <span class="kw">if </span>first_new_index > <span class="number">0 </span>{ |
| <span class="self">self</span>.cumulative_weights[first_new_index - <span class="number">1</span>].clone() |
| } <span class="kw">else </span>{ |
| zero.clone() |
| }; |
| <span class="kw">for </span>i <span class="kw">in </span>first_new_index..<span class="self">self</span>.cumulative_weights.len() { |
| <span class="kw">match </span>next_new_weight { |
| <span class="prelude-val">Some</span>(<span class="kw-2">&</span>(j, w)) <span class="kw">if </span>i == j => { |
| cumulative_weight += w; |
| next_new_weight = iter.next(); |
| } |
| <span class="kw">_ </span>=> { |
| <span class="kw">let </span><span class="kw-2">mut </span>tmp = <span class="self">self</span>.cumulative_weights[i].clone(); |
| tmp -= <span class="kw-2">&</span>prev_weight; <span class="comment">// We know this is positive. |
| </span>cumulative_weight += <span class="kw-2">&</span>tmp; |
| } |
| } |
| prev_weight = cumulative_weight.clone(); |
| core::mem::swap(<span class="kw-2">&mut </span>prev_weight, <span class="kw-2">&mut </span><span class="self">self</span>.cumulative_weights[i]); |
| } |
| |
| <span class="self">self</span>.total_weight = total_weight; |
| <span class="self">self</span>.weight_distribution = X::Sampler::new(zero, <span class="self">self</span>.total_weight.clone()); |
| |
| <span class="prelude-val">Ok</span>(()) |
| } |
| } |
| |
| <span class="kw">impl</span><X> Distribution<usize> <span class="kw">for </span>WeightedIndex<X> |
| <span class="kw">where </span>X: SampleUniform + PartialOrd |
| { |
| <span class="kw">fn </span>sample<R: Rng + <span class="question-mark">?</span>Sized>(<span class="kw-2">&</span><span class="self">self</span>, rng: <span class="kw-2">&mut </span>R) -> usize { |
| <span class="kw">use </span>::core::cmp::Ordering; |
| <span class="kw">let </span>chosen_weight = <span class="self">self</span>.weight_distribution.sample(rng); |
| <span class="comment">// Find the first item which has a weight *higher* than the chosen weight. |
| </span><span class="self">self</span>.cumulative_weights |
| .binary_search_by(|w| { |
| <span class="kw">if </span><span class="kw-2">*</span>w <= chosen_weight { |
| Ordering::Less |
| } <span class="kw">else </span>{ |
| Ordering::Greater |
| } |
| }) |
| .unwrap_err() |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"serde1"</span>)] |
| #[test] |
| </span><span class="kw">fn </span>test_weightedindex_serde1() { |
| <span class="kw">let </span>weighted_index = WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>, <span class="number">10</span>]).unwrap(); |
| |
| <span class="kw">let </span>ser_weighted_index = bincode::serialize(<span class="kw-2">&</span>weighted_index).unwrap(); |
| <span class="kw">let </span>de_weighted_index: WeightedIndex<i32> = |
| bincode::deserialize(<span class="kw-2">&</span>ser_weighted_index).unwrap(); |
| |
| <span class="macro">assert_eq!</span>( |
| de_weighted_index.cumulative_weights, |
| weighted_index.cumulative_weights |
| ); |
| <span class="macro">assert_eq!</span>(de_weighted_index.total_weight, weighted_index.total_weight); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_accepting_nan(){ |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[core::f32::NAN, <span class="number">0.5</span>]).unwrap_err(), |
| WeightedError::InvalidWeight, |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[core::f32::NAN]).unwrap_err(), |
| WeightedError::InvalidWeight, |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">0.5</span>, core::f32::NAN]).unwrap_err(), |
| WeightedError::InvalidWeight, |
| ); |
| |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">0.5</span>, <span class="number">7.0</span>]) |
| .unwrap() |
| .update_weights(<span class="kw-2">&</span>[(<span class="number">0</span>, <span class="kw-2">&</span>core::f32::NAN)]) |
| .unwrap_err(), |
| WeightedError::InvalidWeight, |
| ) |
| } |
| |
| |
| <span class="attribute">#[test] |
| #[cfg_attr(miri, ignore)] </span><span class="comment">// Miri is too slow |
| </span><span class="kw">fn </span>test_weightedindex() { |
| <span class="kw">let </span><span class="kw-2">mut </span>r = <span class="kw">crate</span>::test::rng(<span class="number">700</span>); |
| <span class="kw">const </span>N_REPS: u32 = <span class="number">5000</span>; |
| <span class="kw">let </span>weights = [<span class="number">1u32</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">0</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>]; |
| <span class="kw">let </span>total_weight = weights.iter().sum::<u32>() <span class="kw">as </span>f32; |
| |
| <span class="kw">let </span>verify = |result: [i32; <span class="number">14</span>]| { |
| <span class="kw">for </span>(i, count) <span class="kw">in </span>result.iter().enumerate() { |
| <span class="kw">let </span>exp = (weights[i] * N_REPS) <span class="kw">as </span>f32 / total_weight; |
| <span class="kw">let </span><span class="kw-2">mut </span>err = (<span class="kw-2">*</span>count <span class="kw">as </span>f32 - exp).abs(); |
| <span class="kw">if </span>err != <span class="number">0.0 </span>{ |
| err /= exp; |
| } |
| <span class="macro">assert!</span>(err <= <span class="number">0.25</span>); |
| } |
| }; |
| |
| <span class="comment">// WeightedIndex from vec |
| </span><span class="kw">let </span><span class="kw-2">mut </span>chosen = [<span class="number">0i32</span>; <span class="number">14</span>]; |
| <span class="kw">let </span>distr = WeightedIndex::new(weights.to_vec()).unwrap(); |
| <span class="kw">for _ in </span><span class="number">0</span>..N_REPS { |
| chosen[distr.sample(<span class="kw-2">&mut </span>r)] += <span class="number">1</span>; |
| } |
| verify(chosen); |
| |
| <span class="comment">// WeightedIndex from slice |
| </span>chosen = [<span class="number">0i32</span>; <span class="number">14</span>]; |
| <span class="kw">let </span>distr = WeightedIndex::new(<span class="kw-2">&</span>weights[..]).unwrap(); |
| <span class="kw">for _ in </span><span class="number">0</span>..N_REPS { |
| chosen[distr.sample(<span class="kw-2">&mut </span>r)] += <span class="number">1</span>; |
| } |
| verify(chosen); |
| |
| <span class="comment">// WeightedIndex from iterator |
| </span>chosen = [<span class="number">0i32</span>; <span class="number">14</span>]; |
| <span class="kw">let </span>distr = WeightedIndex::new(weights.iter()).unwrap(); |
| <span class="kw">for _ in </span><span class="number">0</span>..N_REPS { |
| chosen[distr.sample(<span class="kw-2">&mut </span>r)] += <span class="number">1</span>; |
| } |
| verify(chosen); |
| |
| <span class="kw">for _ in </span><span class="number">0</span>..<span class="number">5 </span>{ |
| <span class="macro">assert_eq!</span>(WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">0</span>, <span class="number">1</span>]).unwrap().sample(<span class="kw-2">&mut </span>r), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">0</span>]).unwrap().sample(<span class="kw-2">&mut </span>r), <span class="number">0</span>); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">10</span>, <span class="number">0</span>]) |
| .unwrap() |
| .sample(<span class="kw-2">&mut </span>r), |
| <span class="number">4 |
| </span>); |
| } |
| |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">10</span>][<span class="number">0</span>..<span class="number">0</span>]).unwrap_err(), |
| WeightedError::NoItem |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">0</span>]).unwrap_err(), |
| WeightedError::AllWeightsZero |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">10</span>, <span class="number">20</span>, -<span class="number">1</span>, <span class="number">30</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[-<span class="number">10</span>, <span class="number">20</span>, <span class="number">1</span>, <span class="number">30</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedIndex::new(<span class="kw-2">&</span>[-<span class="number">10</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_update_weights() { |
| <span class="kw">let </span>data = [ |
| ( |
| <span class="kw-2">&</span>[<span class="number">10u32</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>][..], |
| <span class="kw-2">&</span>[(<span class="number">1</span>, <span class="kw-2">&</span><span class="number">100</span>), (<span class="number">2</span>, <span class="kw-2">&</span><span class="number">4</span>)][..], <span class="comment">// positive change |
| </span><span class="kw-2">&</span>[<span class="number">10</span>, <span class="number">100</span>, <span class="number">4</span>, <span class="number">4</span>][..], |
| ), |
| ( |
| <span class="kw-2">&</span>[<span class="number">1u32</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">0</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>][..], |
| <span class="kw-2">&</span>[(<span class="number">2</span>, <span class="kw-2">&</span><span class="number">1</span>), (<span class="number">5</span>, <span class="kw-2">&</span><span class="number">1</span>), (<span class="number">13</span>, <span class="kw-2">&</span><span class="number">100</span>)][..], <span class="comment">// negative change and last element |
| </span><span class="kw-2">&</span>[<span class="number">1u32</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">0</span>, <span class="number">5</span>, <span class="number">1</span>, <span class="number">7</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">100</span>][..], |
| ), |
| ]; |
| |
| <span class="kw">for </span>(weights, update, expected_weights) <span class="kw">in </span>data.iter() { |
| <span class="kw">let </span>total_weight = weights.iter().sum::<u32>(); |
| <span class="kw">let </span><span class="kw-2">mut </span>distr = WeightedIndex::new(weights.to_vec()).unwrap(); |
| <span class="macro">assert_eq!</span>(distr.total_weight, total_weight); |
| |
| distr.update_weights(update).unwrap(); |
| <span class="kw">let </span>expected_total_weight = expected_weights.iter().sum::<u32>(); |
| <span class="kw">let </span>expected_distr = WeightedIndex::new(expected_weights.to_vec()).unwrap(); |
| <span class="macro">assert_eq!</span>(distr.total_weight, expected_total_weight); |
| <span class="macro">assert_eq!</span>(distr.total_weight, expected_distr.total_weight); |
| <span class="macro">assert_eq!</span>(distr.cumulative_weights, expected_distr.cumulative_weights); |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>value_stability() { |
| <span class="kw">fn </span>test_samples<X: SampleUniform + PartialOrd, I>( |
| weights: I, buf: <span class="kw-2">&mut </span>[usize], expected: <span class="kw-2">&</span>[usize], |
| ) <span class="kw">where |
| </span>I: IntoIterator, |
| I::Item: SampleBorrow<X>, |
| X: <span class="kw">for</span><<span class="lifetime">'a</span>> ::core::ops::AddAssign<<span class="kw-2">&</span><span class="lifetime">'a </span>X> + Clone + Default, |
| { |
| <span class="macro">assert_eq!</span>(buf.len(), expected.len()); |
| <span class="kw">let </span>distr = WeightedIndex::new(weights).unwrap(); |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = <span class="kw">crate</span>::test::rng(<span class="number">701</span>); |
| <span class="kw">for </span>r <span class="kw">in </span>buf.iter_mut() { |
| <span class="kw-2">*</span>r = rng.sample(<span class="kw-2">&</span>distr); |
| } |
| <span class="macro">assert_eq!</span>(buf, expected); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>buf = [<span class="number">0</span>; <span class="number">10</span>]; |
| test_samples(<span class="kw-2">&</span>[<span class="number">1i32</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>, <span class="number">1</span>], <span class="kw-2">&mut </span>buf, <span class="kw-2">&</span>[ |
| <span class="number">0</span>, <span class="number">6</span>, <span class="number">2</span>, <span class="number">6</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">2</span>, <span class="number">5</span>, |
| ]); |
| test_samples(<span class="kw-2">&</span>[<span class="number">0.7f32</span>, <span class="number">0.1</span>, <span class="number">0.1</span>, <span class="number">0.1</span>], <span class="kw-2">&mut </span>buf, <span class="kw-2">&</span>[ |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">1</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">0</span>, <span class="number">0</span>, |
| ]); |
| test_samples(<span class="kw-2">&</span>[<span class="number">1.0f64</span>, <span class="number">0.999</span>, <span class="number">0.998</span>, <span class="number">0.997</span>], <span class="kw-2">&mut </span>buf, <span class="kw-2">&</span>[ |
| <span class="number">2</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">3</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">3</span>, <span class="number">3</span>, <span class="number">2</span>, <span class="number">1</span>, |
| ]); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>weighted_index_distributions_can_be_compared() { |
| <span class="macro">assert_eq!</span>(WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>]), WeightedIndex::new(<span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>])); |
| } |
| } |
| |
| <span class="doccomment">/// Error type returned from `WeightedIndex::new`. |
| </span><span class="attribute">#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"alloc"</span>)))] |
| #[derive(Debug, Clone, Copy, PartialEq, Eq)] |
| </span><span class="kw">pub enum </span>WeightedError { |
| <span class="doccomment">/// The provided weight collection contains no items. |
| </span>NoItem, |
| |
| <span class="doccomment">/// A weight is either less than zero, greater than the supported maximum, |
| /// NaN, or otherwise invalid. |
| </span>InvalidWeight, |
| |
| <span class="doccomment">/// All items in the provided weight collection are zero. |
| </span>AllWeightsZero, |
| |
| <span class="doccomment">/// Too many weights are provided (length greater than `u32::MAX`) |
| </span>TooMany, |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">impl </span>std::error::Error <span class="kw">for </span>WeightedError {} |
| |
| <span class="kw">impl </span>fmt::Display <span class="kw">for </span>WeightedError { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| f.write_str(<span class="kw">match </span><span class="kw-2">*</span><span class="self">self </span>{ |
| WeightedError::NoItem => <span class="string">"No weights provided in distribution"</span>, |
| WeightedError::InvalidWeight => <span class="string">"A weight is invalid in distribution"</span>, |
| WeightedError::AllWeightsZero => <span class="string">"All weights are zero in distribution"</span>, |
| WeightedError::TooMany => <span class="string">"Too many weights (hit u32::MAX) in distribution"</span>, |
| }) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="rand" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |