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| <span id="523">523</span> |
| <span id="524">524</span> |
| </pre><pre class="rust"><code><span class="comment">// Copyright 2019 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">//! This module contains an implementation of alias method for sampling random |
| //! indices with probabilities proportional to a collection of weights. |
| |
| </span><span class="kw">use </span><span class="kw">super</span>::WeightedError; |
| <span class="kw">use crate</span>::{uniform::SampleUniform, Distribution, Uniform}; |
| <span class="kw">use </span>core::fmt; |
| <span class="kw">use </span>core::iter::Sum; |
| <span class="kw">use </span>core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign}; |
| <span class="kw">use </span>rand::Rng; |
| <span class="kw">use </span>alloc::{boxed::Box, vec, 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 to pick a discretely selected item. |
| /// |
| /// Sampling a [`WeightedAliasIndex<W>`] distribution returns the index of a randomly |
| /// selected element from the vector used to create the [`WeightedAliasIndex<W>`]. |
| /// The chance of a given element being picked is proportional to the value of |
| /// the element. The weights can have any type `W` for which a implementation of |
| /// [`AliasableWeight`] exists. |
| /// |
| /// # Performance |
| /// |
| /// Given that `n` is the number of items in the vector used to create an |
| /// [`WeightedAliasIndex<W>`], it will require `O(n)` amount of memory. |
| /// More specifically it takes up some constant amount of memory plus |
| /// the vector used to create it and a [`Vec<u32>`] with capacity `n`. |
| /// |
| /// Time complexity for the creation of a [`WeightedAliasIndex<W>`] is `O(n)`. |
| /// Sampling is `O(1)`, it makes a call to [`Uniform<u32>::sample`] and a call |
| /// to [`Uniform<W>::sample`]. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use rand_distr::WeightedAliasIndex; |
| /// use rand::prelude::*; |
| /// |
| /// let choices = vec!['a', 'b', 'c']; |
| /// let weights = vec![2, 1, 1]; |
| /// let dist = WeightedAliasIndex::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 = WeightedAliasIndex::new(items.iter().map(|item| item.1).collect()).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); |
| /// } |
| /// ``` |
| /// |
| /// [`WeightedAliasIndex<W>`]: WeightedAliasIndex |
| /// [`Vec<u32>`]: Vec |
| /// [`Uniform<u32>::sample`]: Distribution::sample |
| /// [`Uniform<W>::sample`]: Distribution::sample |
| </span><span class="attribute">#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"alloc"</span>)))] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, derive(Serialize, Deserialize))] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, serde(bound(serialize = <span class="string">"W: Serialize, W::Sampler: Serialize"</span>)))] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, serde(bound(deserialize = <span class="string">"W: Deserialize<'de>, W::Sampler: Deserialize<'de>"</span>)))] |
| </span><span class="kw">pub struct </span>WeightedAliasIndex<W: AliasableWeight> { |
| aliases: Box<[u32]>, |
| no_alias_odds: Box<[W]>, |
| uniform_index: Uniform<u32>, |
| uniform_within_weight_sum: Uniform<W>, |
| } |
| |
| <span class="kw">impl</span><W: AliasableWeight> WeightedAliasIndex<W> { |
| <span class="doccomment">/// Creates a new [`WeightedAliasIndex`]. |
| /// |
| /// Returns an error if: |
| /// - The vector is empty. |
| /// - The vector is longer than `u32::MAX`. |
| /// - For any weight `w`: `w < 0` or `w > max` where `max = W::MAX / |
| /// weights.len()`. |
| /// - The sum of weights is zero. |
| </span><span class="kw">pub fn </span>new(weights: Vec<W>) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, WeightedError> { |
| <span class="kw">let </span>n = weights.len(); |
| <span class="kw">if </span>n == <span class="number">0 </span>{ |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::NoItem); |
| } <span class="kw">else if </span>n > ::core::u32::MAX <span class="kw">as </span>usize { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::TooMany); |
| } |
| <span class="kw">let </span>n = n <span class="kw">as </span>u32; |
| |
| <span class="kw">let </span>max_weight_size = W::try_from_u32_lossy(n) |
| .map(|n| W::MAX / n) |
| .unwrap_or(W::ZERO); |
| <span class="kw">if </span>!weights |
| .iter() |
| .all(|<span class="kw-2">&</span>w| W::ZERO <= w && w <= max_weight_size) |
| { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::InvalidWeight); |
| } |
| |
| <span class="comment">// The sum of weights will represent 100% of no alias odds. |
| </span><span class="kw">let </span>weight_sum = AliasableWeight::sum(weights.as_slice()); |
| <span class="comment">// Prevent floating point overflow due to rounding errors. |
| </span><span class="kw">let </span>weight_sum = <span class="kw">if </span>weight_sum > W::MAX { |
| W::MAX |
| } <span class="kw">else </span>{ |
| weight_sum |
| }; |
| <span class="kw">if </span>weight_sum == W::ZERO { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(WeightedError::AllWeightsZero); |
| } |
| |
| <span class="comment">// `weight_sum` would have been zero if `try_from_lossy` causes an error here. |
| </span><span class="kw">let </span>n_converted = W::try_from_u32_lossy(n).unwrap(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>no_alias_odds = weights.into_boxed_slice(); |
| <span class="kw">for </span>odds <span class="kw">in </span>no_alias_odds.iter_mut() { |
| <span class="kw-2">*</span>odds <span class="kw-2">*</span>= n_converted; |
| <span class="comment">// Prevent floating point overflow due to rounding errors. |
| </span><span class="kw-2">*</span>odds = <span class="kw">if </span><span class="kw-2">*</span>odds > W::MAX { W::MAX } <span class="kw">else </span>{ <span class="kw-2">*</span>odds }; |
| } |
| |
| <span class="doccomment">/// This struct is designed to contain three data structures at once, |
| /// sharing the same memory. More precisely it contains two linked lists |
| /// and an alias map, which will be the output of this method. To keep |
| /// the three data structures from getting in each other's way, it must |
| /// be ensured that a single index is only ever in one of them at the |
| /// same time. |
| </span><span class="kw">struct </span>Aliases { |
| aliases: Box<[u32]>, |
| smalls_head: u32, |
| bigs_head: u32, |
| } |
| |
| <span class="kw">impl </span>Aliases { |
| <span class="kw">fn </span>new(size: u32) -> <span class="self">Self </span>{ |
| Aliases { |
| aliases: <span class="macro">vec!</span>[<span class="number">0</span>; size <span class="kw">as </span>usize].into_boxed_slice(), |
| smalls_head: ::core::u32::MAX, |
| bigs_head: ::core::u32::MAX, |
| } |
| } |
| |
| <span class="kw">fn </span>push_small(<span class="kw-2">&mut </span><span class="self">self</span>, idx: u32) { |
| <span class="self">self</span>.aliases[idx <span class="kw">as </span>usize] = <span class="self">self</span>.smalls_head; |
| <span class="self">self</span>.smalls_head = idx; |
| } |
| |
| <span class="kw">fn </span>push_big(<span class="kw-2">&mut </span><span class="self">self</span>, idx: u32) { |
| <span class="self">self</span>.aliases[idx <span class="kw">as </span>usize] = <span class="self">self</span>.bigs_head; |
| <span class="self">self</span>.bigs_head = idx; |
| } |
| |
| <span class="kw">fn </span>pop_small(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| <span class="kw">let </span>popped = <span class="self">self</span>.smalls_head; |
| <span class="self">self</span>.smalls_head = <span class="self">self</span>.aliases[popped <span class="kw">as </span>usize]; |
| popped |
| } |
| |
| <span class="kw">fn </span>pop_big(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| <span class="kw">let </span>popped = <span class="self">self</span>.bigs_head; |
| <span class="self">self</span>.bigs_head = <span class="self">self</span>.aliases[popped <span class="kw">as </span>usize]; |
| popped |
| } |
| |
| <span class="kw">fn </span>smalls_is_empty(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.smalls_head == ::core::u32::MAX |
| } |
| |
| <span class="kw">fn </span>bigs_is_empty(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.bigs_head == ::core::u32::MAX |
| } |
| |
| <span class="kw">fn </span>set_alias(<span class="kw-2">&mut </span><span class="self">self</span>, idx: u32, alias: u32) { |
| <span class="self">self</span>.aliases[idx <span class="kw">as </span>usize] = alias; |
| } |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>aliases = Aliases::new(n); |
| |
| <span class="comment">// Split indices into those with small weights and those with big weights. |
| </span><span class="kw">for </span>(index, <span class="kw-2">&</span>odds) <span class="kw">in </span>no_alias_odds.iter().enumerate() { |
| <span class="kw">if </span>odds < weight_sum { |
| aliases.push_small(index <span class="kw">as </span>u32); |
| } <span class="kw">else </span>{ |
| aliases.push_big(index <span class="kw">as </span>u32); |
| } |
| } |
| |
| <span class="comment">// Build the alias map by finding an alias with big weight for each index with |
| // small weight. |
| </span><span class="kw">while </span>!aliases.smalls_is_empty() && !aliases.bigs_is_empty() { |
| <span class="kw">let </span>s = aliases.pop_small(); |
| <span class="kw">let </span>b = aliases.pop_big(); |
| |
| aliases.set_alias(s, b); |
| no_alias_odds[b <span class="kw">as </span>usize] = |
| no_alias_odds[b <span class="kw">as </span>usize] - weight_sum + no_alias_odds[s <span class="kw">as </span>usize]; |
| |
| <span class="kw">if </span>no_alias_odds[b <span class="kw">as </span>usize] < weight_sum { |
| aliases.push_small(b); |
| } <span class="kw">else </span>{ |
| aliases.push_big(b); |
| } |
| } |
| |
| <span class="comment">// The remaining indices should have no alias odds of about 100%. This is due to |
| // numeric accuracy. Otherwise they would be exactly 100%. |
| </span><span class="kw">while </span>!aliases.smalls_is_empty() { |
| no_alias_odds[aliases.pop_small() <span class="kw">as </span>usize] = weight_sum; |
| } |
| <span class="kw">while </span>!aliases.bigs_is_empty() { |
| no_alias_odds[aliases.pop_big() <span class="kw">as </span>usize] = weight_sum; |
| } |
| |
| <span class="comment">// Prepare distributions for sampling. Creating them beforehand improves |
| // sampling performance. |
| </span><span class="kw">let </span>uniform_index = Uniform::new(<span class="number">0</span>, n); |
| <span class="kw">let </span>uniform_within_weight_sum = Uniform::new(W::ZERO, weight_sum); |
| |
| <span class="prelude-val">Ok</span>(<span class="self">Self </span>{ |
| aliases: aliases.aliases, |
| no_alias_odds, |
| uniform_index, |
| uniform_within_weight_sum, |
| }) |
| } |
| } |
| |
| <span class="kw">impl</span><W: AliasableWeight> Distribution<usize> <span class="kw">for </span>WeightedAliasIndex<W> { |
| <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">let </span>candidate = rng.sample(<span class="self">self</span>.uniform_index); |
| <span class="kw">if </span>rng.sample(<span class="kw-2">&</span><span class="self">self</span>.uniform_within_weight_sum) < <span class="self">self</span>.no_alias_odds[candidate <span class="kw">as </span>usize] { |
| candidate <span class="kw">as </span>usize |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.aliases[candidate <span class="kw">as </span>usize] <span class="kw">as </span>usize |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><W: AliasableWeight> fmt::Debug <span class="kw">for </span>WeightedAliasIndex<W> |
| <span class="kw">where |
| </span>W: fmt::Debug, |
| Uniform<W>: fmt::Debug, |
| { |
| <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.debug_struct(<span class="string">"WeightedAliasIndex"</span>) |
| .field(<span class="string">"aliases"</span>, <span class="kw-2">&</span><span class="self">self</span>.aliases) |
| .field(<span class="string">"no_alias_odds"</span>, <span class="kw-2">&</span><span class="self">self</span>.no_alias_odds) |
| .field(<span class="string">"uniform_index"</span>, <span class="kw-2">&</span><span class="self">self</span>.uniform_index) |
| .field(<span class="string">"uniform_within_weight_sum"</span>, <span class="kw-2">&</span><span class="self">self</span>.uniform_within_weight_sum) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl</span><W: AliasableWeight> Clone <span class="kw">for </span>WeightedAliasIndex<W> |
| <span class="kw">where </span>Uniform<W>: Clone |
| { |
| <span class="kw">fn </span>clone(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| aliases: <span class="self">self</span>.aliases.clone(), |
| no_alias_odds: <span class="self">self</span>.no_alias_odds.clone(), |
| uniform_index: <span class="self">self</span>.uniform_index, |
| uniform_within_weight_sum: <span class="self">self</span>.uniform_within_weight_sum.clone(), |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Trait that must be implemented for weights, that are used with |
| /// [`WeightedAliasIndex`]. Currently no guarantees on the correctness of |
| /// [`WeightedAliasIndex`] are given for custom implementations of this trait. |
| </span><span class="attribute">#[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"alloc"</span>)))] |
| </span><span class="kw">pub trait </span>AliasableWeight: |
| Sized |
| + Copy |
| + SampleUniform |
| + PartialOrd |
| + Add<Output = <span class="self">Self</span>> |
| + AddAssign |
| + Sub<Output = <span class="self">Self</span>> |
| + SubAssign |
| + Mul<Output = <span class="self">Self</span>> |
| + MulAssign |
| + Div<Output = <span class="self">Self</span>> |
| + DivAssign |
| + Sum |
| { |
| <span class="doccomment">/// Maximum number representable by `Self`. |
| </span><span class="kw">const </span>MAX: <span class="self">Self</span>; |
| |
| <span class="doccomment">/// Element of `Self` equivalent to 0. |
| </span><span class="kw">const </span>ZERO: <span class="self">Self</span>; |
| |
| <span class="doccomment">/// Produce an instance of `Self` from a `u32` value, or return `None` if |
| /// out of range. Loss of precision (where `Self` is a floating point type) |
| /// is acceptable. |
| </span><span class="kw">fn </span>try_from_u32_lossy(n: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>; |
| |
| <span class="doccomment">/// Sums all values in slice `values`. |
| </span><span class="kw">fn </span>sum(values: <span class="kw-2">&</span>[<span class="self">Self</span>]) -> <span class="self">Self </span>{ |
| values.iter().copied().sum() |
| } |
| } |
| |
| <span class="macro">macro_rules! </span>impl_weight_for_float { |
| (<span class="macro-nonterminal">$T</span>: ident) => { |
| <span class="kw">impl </span>AliasableWeight <span class="kw">for </span><span class="macro-nonterminal">$T </span>{ |
| <span class="kw">const </span>MAX: <span class="self">Self </span>= ::core::<span class="macro-nonterminal">$T::MAX</span>; |
| <span class="kw">const </span>ZERO: <span class="self">Self </span>= <span class="number">0.0</span>; |
| |
| <span class="kw">fn </span>try_from_u32_lossy(n: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>> { |
| <span class="prelude-val">Some</span>(n <span class="kw">as </span><span class="macro-nonterminal">$T</span>) |
| } |
| |
| <span class="kw">fn </span>sum(values: <span class="kw-2">&</span>[<span class="self">Self</span>]) -> <span class="self">Self </span>{ |
| pairwise_sum(values) |
| } |
| } |
| }; |
| } |
| |
| <span class="doccomment">/// In comparison to naive accumulation, the pairwise sum algorithm reduces |
| /// rounding errors when there are many floating point values. |
| </span><span class="kw">fn </span>pairwise_sum<T: AliasableWeight>(values: <span class="kw-2">&</span>[T]) -> T { |
| <span class="kw">if </span>values.len() <= <span class="number">32 </span>{ |
| values.iter().copied().sum() |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>mid = values.len() / <span class="number">2</span>; |
| <span class="kw">let </span>(a, b) = values.split_at(mid); |
| pairwise_sum(a) + pairwise_sum(b) |
| } |
| } |
| |
| <span class="macro">macro_rules! </span>impl_weight_for_int { |
| (<span class="macro-nonterminal">$T</span>: ident) => { |
| <span class="kw">impl </span>AliasableWeight <span class="kw">for </span><span class="macro-nonterminal">$T </span>{ |
| <span class="kw">const </span>MAX: <span class="self">Self </span>= ::core::<span class="macro-nonterminal">$T::MAX</span>; |
| <span class="kw">const </span>ZERO: <span class="self">Self </span>= <span class="number">0</span>; |
| |
| <span class="kw">fn </span>try_from_u32_lossy(n: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>> { |
| <span class="kw">let </span>n_converted = n <span class="kw">as </span><span class="self">Self</span>; |
| <span class="kw">if </span>n_converted >= <span class="self">Self</span>::ZERO && n_converted <span class="kw">as </span>u32 == n { |
| <span class="prelude-val">Some</span>(n_converted) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| } |
| }; |
| } |
| |
| <span class="macro">impl_weight_for_float!</span>(f64); |
| <span class="macro">impl_weight_for_float!</span>(f32); |
| <span class="macro">impl_weight_for_int!</span>(usize); |
| <span class="macro">impl_weight_for_int!</span>(u128); |
| <span class="macro">impl_weight_for_int!</span>(u64); |
| <span class="macro">impl_weight_for_int!</span>(u32); |
| <span class="macro">impl_weight_for_int!</span>(u16); |
| <span class="macro">impl_weight_for_int!</span>(u8); |
| <span class="macro">impl_weight_for_int!</span>(isize); |
| <span class="macro">impl_weight_for_int!</span>(i128); |
| <span class="macro">impl_weight_for_int!</span>(i64); |
| <span class="macro">impl_weight_for_int!</span>(i32); |
| <span class="macro">impl_weight_for_int!</span>(i16); |
| <span class="macro">impl_weight_for_int!</span>(i8); |
| |
| <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">#[test] |
| #[cfg_attr(miri, ignore)] </span><span class="comment">// Miri is too slow |
| </span><span class="kw">fn </span>test_weighted_index_f32() { |
| test_weighted_index(f32::into); |
| |
| <span class="comment">// Floating point special cases |
| </span><span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[::core::f32::INFINITY]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[-<span class="number">0_f32</span>]).unwrap_err(), |
| WeightedError::AllWeightsZero |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[-<span class="number">1_f32</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[-::core::f32::INFINITY]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</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_weighted_index_u128() { |
| test_weighted_index(|x: u128| x <span class="kw">as </span>f64); |
| } |
| |
| <span class="attribute">#[test] |
| #[cfg_attr(miri, ignore)] </span><span class="comment">// Miri is too slow |
| </span><span class="kw">fn </span>test_weighted_index_i128() { |
| test_weighted_index(|x: i128| x <span class="kw">as </span>f64); |
| |
| <span class="comment">// Signed integer special cases |
| </span><span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[-<span class="number">1_i128</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[::core::i128::MIN]).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_weighted_index_u8() { |
| test_weighted_index(u8::into); |
| } |
| |
| <span class="attribute">#[test] |
| #[cfg_attr(miri, ignore)] </span><span class="comment">// Miri is too slow |
| </span><span class="kw">fn </span>test_weighted_index_i8() { |
| test_weighted_index(i8::into); |
| |
| <span class="comment">// Signed integer special cases |
| </span><span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[-<span class="number">1_i8</span>]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[::core::i8::MIN]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| } |
| |
| <span class="kw">fn </span>test_weighted_index<W: AliasableWeight, F: Fn(W) -> f64>(w_to_f64: F) |
| <span class="kw">where </span>WeightedAliasIndex<W>: fmt::Debug { |
| <span class="kw">const </span>NUM_WEIGHTS: u32 = <span class="number">10</span>; |
| <span class="kw">const </span>ZERO_WEIGHT_INDEX: u32 = <span class="number">3</span>; |
| <span class="kw">const </span>NUM_SAMPLES: u32 = <span class="number">15000</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = <span class="kw">crate</span>::test::rng(<span class="number">0x9c9fa0b0580a7031</span>); |
| |
| <span class="kw">let </span>weights = { |
| <span class="kw">let </span><span class="kw-2">mut </span>weights = Vec::with_capacity(NUM_WEIGHTS <span class="kw">as </span>usize); |
| <span class="kw">let </span>random_weight_distribution = Uniform::new_inclusive( |
| W::ZERO, |
| W::MAX / W::try_from_u32_lossy(NUM_WEIGHTS).unwrap(), |
| ); |
| <span class="kw">for _ in </span><span class="number">0</span>..NUM_WEIGHTS { |
| weights.push(rng.sample(<span class="kw-2">&</span>random_weight_distribution)); |
| } |
| weights[ZERO_WEIGHT_INDEX <span class="kw">as </span>usize] = W::ZERO; |
| weights |
| }; |
| <span class="kw">let </span>weight_sum = weights.iter().copied().sum::<W>(); |
| <span class="kw">let </span>expected_counts = weights |
| .iter() |
| .map(|<span class="kw-2">&</span>w| w_to_f64(w) / w_to_f64(weight_sum) * NUM_SAMPLES <span class="kw">as </span>f64) |
| .collect::<Vec<f64>>(); |
| <span class="kw">let </span>weight_distribution = WeightedAliasIndex::new(weights).unwrap(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>counts = <span class="macro">vec!</span>[<span class="number">0</span>; NUM_WEIGHTS <span class="kw">as </span>usize]; |
| <span class="kw">for _ in </span><span class="number">0</span>..NUM_SAMPLES { |
| counts[rng.sample(<span class="kw-2">&</span>weight_distribution)] += <span class="number">1</span>; |
| } |
| |
| <span class="macro">assert_eq!</span>(counts[ZERO_WEIGHT_INDEX <span class="kw">as </span>usize], <span class="number">0</span>); |
| <span class="kw">for </span>(count, expected_count) <span class="kw">in </span>counts.into_iter().zip(expected_counts) { |
| <span class="kw">let </span>difference = (count <span class="kw">as </span>f64 - expected_count).abs(); |
| <span class="kw">let </span>max_allowed_difference = NUM_SAMPLES <span class="kw">as </span>f64 / NUM_WEIGHTS <span class="kw">as </span>f64 * <span class="number">0.1</span>; |
| <span class="macro">assert!</span>(difference <= max_allowed_difference); |
| } |
| |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::<W>::new(<span class="macro">vec!</span>[]).unwrap_err(), |
| WeightedError::NoItem |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[W::ZERO]).unwrap_err(), |
| WeightedError::AllWeightsZero |
| ); |
| <span class="macro">assert_eq!</span>( |
| WeightedAliasIndex::new(<span class="macro">vec!</span>[W::MAX, W::MAX]).unwrap_err(), |
| WeightedError::InvalidWeight |
| ); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>value_stability() { |
| <span class="kw">fn </span>test_samples<W: AliasableWeight>(weights: Vec<W>, buf: <span class="kw-2">&mut </span>[usize], expected: <span class="kw-2">&</span>[usize]) { |
| <span class="macro">assert_eq!</span>(buf.len(), expected.len()); |
| <span class="kw">let </span>distr = WeightedAliasIndex::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">0x9c9fa0b0580a7031</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="macro">vec!</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">6</span>, <span class="number">5</span>, <span class="number">7</span>, <span class="number">5</span>, <span class="number">8</span>, <span class="number">7</span>, <span class="number">6</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">7</span>, |
| ]); |
| test_samples(<span class="macro">vec!</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">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">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">1</span>, <span class="number">3</span>, |
| ]); |
| test_samples(<span class="macro">vec!</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">1</span>, <span class="number">2</span>, <span class="number">3</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">1</span>, |
| ]); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="rand_distr" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |