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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/git/checkouts/incubator-teaclave-crates-c8106113f74feefc/ede1f68/rand/src/distributions/weighted_index.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>weighted_index.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../rand/index.html"><div class="logo-container">
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<img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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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 &lt;LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0&gt; or the MIT license
// &lt;LICENSE-MIT or https://opensource.org/licenses/MIT&gt;, 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=&quot;alloc&quot; is enabled.
</span><span class="kw">use </span>alloc::vec::Vec;
<span class="attribute">#[cfg(feature = <span class="string">&quot;serde1&quot;</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&lt;X&gt;`] 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&lt;X&gt;` contains a `Vec&lt;X&gt;` and a [`Uniform&lt;X&gt;`] and so its
/// size is the sum of the size of those objects, possibly plus some alignment.
///
/// Creating a `WeightedIndex&lt;X&gt;` will allocate enough space to hold `N - 1`
/// weights of type `X`, where `N` is the number of weights. However, since
/// `Vec` doesn&#39;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&lt;X&gt;`] doesn&#39;t allocate any memory.
///
/// Sampling from `WeightedIndex` will result in a single call to
/// `Uniform&lt;X&gt;::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&lt;X&gt;::sample`.
///
/// # Example
///
/// ```
/// use rand::prelude::*;
/// use rand::distributions::WeightedIndex;
///
/// let choices = [&#39;a&#39;, &#39;b&#39;, &#39;c&#39;];
/// let weights = [2, 1, 1];
/// let dist = WeightedIndex::new(&amp;weights).unwrap();
/// let mut rng = thread_rng();
/// for _ in 0..100 {
/// // 50% chance to print &#39;a&#39;, 25% chance to print &#39;b&#39;, 25% chance to print &#39;c&#39;
/// println!(&quot;{}&quot;, choices[dist.sample(&amp;mut rng)]);
/// }
///
/// let items = [(&#39;a&#39;, 0), (&#39;b&#39;, 3), (&#39;c&#39;, 7)];
/// let dist2 = WeightedIndex::new(items.iter().map(|item| item.1)).unwrap();
/// for _ in 0..100 {
/// // 0% chance to print &#39;a&#39;, 30% chance to print &#39;b&#39;, 70% chance to print &#39;c&#39;
/// println!(&quot;{}&quot;, items[dist2.sample(&amp;mut rng)].0);
/// }
/// ```
///
/// [`Uniform&lt;X&gt;`]: crate::distributions::Uniform
/// [`RngCore`]: crate::RngCore
</span><span class="attribute">#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(feature = <span class="string">&quot;serde1&quot;</span>, derive(Serialize, Deserialize))]
#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">&quot;alloc&quot;</span>)))]
</span><span class="kw">pub struct </span>WeightedIndex&lt;X: SampleUniform + PartialOrd&gt; {
cumulative_weights: Vec&lt;X&gt;,
total_weight: X,
weight_distribution: X::Sampler,
}
<span class="kw">impl</span>&lt;X: SampleUniform + PartialOrd&gt; WeightedIndex&lt;X&gt; {
<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&lt;X&gt;`] exists.
///
/// Returns an error if the iterator is empty, if any weight is `&lt; 0`, or
/// if its total value is 0.
///
/// [`Uniform&lt;X&gt;`]: crate::distributions::uniform::Uniform
</span><span class="kw">pub fn </span>new&lt;I&gt;(weights: I) -&gt; <span class="prelude-ty">Result</span>&lt;WeightedIndex&lt;X&gt;, WeightedError&gt;
<span class="kw">where
</span>I: IntoIterator,
I::Item: SampleBorrow&lt;X&gt;,
X: <span class="kw">for</span>&lt;<span class="lifetime">&#39;a</span>&gt; ::core::ops::AddAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>X&gt; + 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 = &lt;X <span class="kw">as </span>Default&gt;::default();
<span class="kw">if </span>!(total_weight &gt;= 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::&lt;X&gt;::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 &gt;= x)` is not equivalent to `w &lt; x` for partially
// ordered types due to NaNs which are equal to nothing.
</span><span class="kw">if </span>!(w.borrow() &gt;= <span class="kw-2">&amp;</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">&amp;mut </span><span class="self">self</span>, new_weights: <span class="kw-2">&amp;</span>[(usize, <span class="kw-2">&amp;</span>X)]) -&gt; <span class="prelude-ty">Result</span>&lt;(), WeightedError&gt;
<span class="kw">where </span>X: <span class="kw">for</span>&lt;<span class="lifetime">&#39;a</span>&gt; ::core::ops::AddAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>X&gt;
+ <span class="kw">for</span>&lt;<span class="lifetime">&#39;a</span>&gt; ::core::ops::SubAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>X&gt;
+ 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 = &lt;X <span class="kw">as </span>Default&gt;::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&#39;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">&amp;</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 &gt;= 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 &gt;= zero) {
<span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight);
}
<span class="kw">if </span>i &gt; <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 &lt; <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 &gt; <span class="number">0 </span>{
old_w -= <span class="kw-2">&amp;</span><span class="self">self</span>.cumulative_weights[i - <span class="number">1</span>];
}
total_weight -= <span class="kw-2">&amp;</span>old_w;
total_weight += w;
prev_i = <span class="prelude-val">Some</span>(i);
}
<span class="kw">if </span>total_weight &lt;= 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">&amp;</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 &gt; <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">&amp;</span>(j, w)) <span class="kw">if </span>i == j =&gt; {
cumulative_weight += w;
next_new_weight = iter.next();
}
<span class="kw">_ </span>=&gt; {
<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">&amp;</span>prev_weight; <span class="comment">// We know this is positive.
</span>cumulative_weight += <span class="kw-2">&amp;</span>tmp;
}
}
prev_weight = cumulative_weight.clone();
core::mem::swap(<span class="kw-2">&amp;mut </span>prev_weight, <span class="kw-2">&amp;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>&lt;X&gt; Distribution&lt;usize&gt; <span class="kw">for </span>WeightedIndex&lt;X&gt;
<span class="kw">where </span>X: SampleUniform + PartialOrd
{
<span class="kw">fn </span>sample&lt;R: Rng + <span class="question-mark">?</span>Sized&gt;(<span class="kw-2">&amp;</span><span class="self">self</span>, rng: <span class="kw-2">&amp;mut </span>R) -&gt; 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 &lt;= 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">&quot;serde1&quot;</span>)]
#[test]
</span><span class="kw">fn </span>test_weightedindex_serde1() {
<span class="kw">let </span>weighted_index = WeightedIndex::new(<span class="kw-2">&amp;</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">&amp;</span>weighted_index).unwrap();
<span class="kw">let </span>de_weighted_index: WeightedIndex&lt;i32&gt; =
bincode::deserialize(<span class="kw-2">&amp;</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">&amp;</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">&amp;</span>[core::f32::NAN]).unwrap_err(),
WeightedError::InvalidWeight,
);
<span class="macro">assert_eq!</span>(
WeightedIndex::new(<span class="kw-2">&amp;</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">&amp;</span>[<span class="number">0.5</span>, <span class="number">7.0</span>])
.unwrap()
.update_weights(<span class="kw-2">&amp;</span>[(<span class="number">0</span>, <span class="kw-2">&amp;</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::&lt;u32&gt;() <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 &lt;= <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">&amp;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">&amp;</span>weights[..]).unwrap();
<span class="kw">for _ in </span><span class="number">0</span>..N_REPS {
chosen[distr.sample(<span class="kw-2">&amp;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">&amp;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">&amp;</span>[<span class="number">0</span>, <span class="number">1</span>]).unwrap().sample(<span class="kw-2">&amp;mut </span>r), <span class="number">1</span>);
<span class="macro">assert_eq!</span>(WeightedIndex::new(<span class="kw-2">&amp;</span>[<span class="number">1</span>, <span class="number">0</span>]).unwrap().sample(<span class="kw-2">&amp;mut </span>r), <span class="number">0</span>);
<span class="macro">assert_eq!</span>(
WeightedIndex::new(<span class="kw-2">&amp;</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">&amp;mut </span>r),
<span class="number">4
</span>);
}
<span class="macro">assert_eq!</span>(
WeightedIndex::new(<span class="kw-2">&amp;</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">&amp;</span>[<span class="number">0</span>]).unwrap_err(),
WeightedError::AllWeightsZero
);
<span class="macro">assert_eq!</span>(
WeightedIndex::new(<span class="kw-2">&amp;</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">&amp;</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">&amp;</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">&amp;</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">&amp;</span>[(<span class="number">1</span>, <span class="kw-2">&amp;</span><span class="number">100</span>), (<span class="number">2</span>, <span class="kw-2">&amp;</span><span class="number">4</span>)][..], <span class="comment">// positive change
</span><span class="kw-2">&amp;</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">&amp;</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">&amp;</span>[(<span class="number">2</span>, <span class="kw-2">&amp;</span><span class="number">1</span>), (<span class="number">5</span>, <span class="kw-2">&amp;</span><span class="number">1</span>), (<span class="number">13</span>, <span class="kw-2">&amp;</span><span class="number">100</span>)][..], <span class="comment">// negative change and last element
</span><span class="kw-2">&amp;</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::&lt;u32&gt;();
<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::&lt;u32&gt;();
<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&lt;X: SampleUniform + PartialOrd, I&gt;(
weights: I, buf: <span class="kw-2">&amp;mut </span>[usize], expected: <span class="kw-2">&amp;</span>[usize],
) <span class="kw">where
</span>I: IntoIterator,
I::Item: SampleBorrow&lt;X&gt;,
X: <span class="kw">for</span>&lt;<span class="lifetime">&#39;a</span>&gt; ::core::ops::AddAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>X&gt; + 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">&amp;</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">&amp;</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">&amp;mut </span>buf, <span class="kw-2">&amp;</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">&amp;</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">&amp;mut </span>buf, <span class="kw-2">&amp;</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">&amp;</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">&amp;mut </span>buf, <span class="kw-2">&amp;</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">&amp;</span>[<span class="number">1</span>, <span class="number">2</span>]), WeightedIndex::new(<span class="kw-2">&amp;</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">&quot;alloc&quot;</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">&quot;std&quot;</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">&amp;</span><span class="self">self</span>, f: <span class="kw-2">&amp;mut </span>fmt::Formatter) -&gt; fmt::Result {
f.write_str(<span class="kw">match </span><span class="kw-2">*</span><span class="self">self </span>{
WeightedError::NoItem =&gt; <span class="string">&quot;No weights provided in distribution&quot;</span>,
WeightedError::InvalidWeight =&gt; <span class="string">&quot;A weight is invalid in distribution&quot;</span>,
WeightedError::AllWeightsZero =&gt; <span class="string">&quot;All weights are zero in distribution&quot;</span>,
WeightedError::TooMany =&gt; <span class="string">&quot;Too many weights (hit u32::MAX) in distribution&quot;</span>,
})
}
}
</code></pre></div>
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