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authorDaniel Mueller <deso@posteo.net>2020-04-04 14:39:19 -0700
committerDaniel Mueller <deso@posteo.net>2020-04-04 14:39:19 -0700
commitd0d9683df8398696147e7ee1fcffb2e4e957008c (patch)
tree4baa76712a76f4d072ee3936c07956580b230820 /rand/src/distributions/weighted/mod.rs
parent203e691f46d591a2cc8acdfd850fa9f5b0fb8a98 (diff)
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Remove vendored dependencies
While it appears that by now we actually can get successful builds without Cargo insisting on Internet access by virtue of using the --frozen flag, maintaining vendored dependencies is somewhat of a pain point. This state will also get worse with upcoming changes that replace argparse in favor of structopt and pull in a slew of new dependencies by doing so. Then there is also the repository structure aspect, which is non-standard due to the way we vendor dependencies and a potential source of confusion. In order to fix these problems, this change removes all the vendored dependencies we have. Delete subrepo argparse/:argparse Delete subrepo base32/:base32 Delete subrepo cc/:cc Delete subrepo cfg-if/:cfg-if Delete subrepo getrandom/:getrandom Delete subrepo lazy-static/:lazy-static Delete subrepo libc/:libc Delete subrepo nitrokey-sys/:nitrokey-sys Delete subrepo nitrokey/:nitrokey Delete subrepo rand/:rand
Diffstat (limited to 'rand/src/distributions/weighted/mod.rs')
-rw-r--r--rand/src/distributions/weighted/mod.rs363
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diff --git a/rand/src/distributions/weighted/mod.rs b/rand/src/distributions/weighted/mod.rs
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-// 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.
-
-//! Weighted index sampling
-//!
-//! This module provides two implementations for sampling indices:
-//!
-//! * [`WeightedIndex`] allows `O(log N)` sampling
-//! * [`alias_method::WeightedIndex`] allows `O(1)` sampling, but with
-//! much greater set-up cost
-//!
-//! [`alias_method::WeightedIndex`]: alias_method/struct.WeightedIndex.html
-
-pub mod alias_method;
-
-use crate::Rng;
-use crate::distributions::Distribution;
-use crate::distributions::uniform::{UniformSampler, SampleUniform, SampleBorrow};
-use core::cmp::PartialOrd;
-use core::fmt;
-
-// Note that this whole module is only imported if feature="alloc" is enabled.
-#[cfg(not(feature="std"))] use crate::alloc::vec::Vec;
-
-/// A distribution using weighted sampling to pick a discretely selected
-/// item.
-///
-/// 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
-///
-/// 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.
-///
-/// Time complexity of sampling from `WeightedIndex` is `O(log N)` where
-/// `N` is the number of weights.
-///
-/// 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 implementaiton 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::Uniform
-/// [`RngCore`]: crate::RngCore
-#[derive(Debug, Clone)]
-pub struct WeightedIndex<X: SampleUniform + PartialOrd> {
- cumulative_weights: Vec<X>,
- total_weight: X,
- weight_distribution: X::Sampler,
-}
-
-impl<X: SampleUniform + PartialOrd> WeightedIndex<X> {
- /// 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
- pub fn new<I>(weights: I) -> Result<WeightedIndex<X>, WeightedError>
- where I: IntoIterator,
- I::Item: SampleBorrow<X>,
- X: for<'a> ::core::ops::AddAssign<&'a X> +
- Clone +
- Default {
- let mut iter = weights.into_iter();
- let mut total_weight: X = iter.next()
- .ok_or(WeightedError::NoItem)?
- .borrow()
- .clone();
-
- let zero = <X as Default>::default();
- if total_weight < zero {
- return Err(WeightedError::InvalidWeight);
- }
-
- let mut weights = Vec::<X>::with_capacity(iter.size_hint().0);
- for w in iter {
- if *w.borrow() < zero {
- return Err(WeightedError::InvalidWeight);
- }
- weights.push(total_weight.clone());
- total_weight += w.borrow();
- }
-
- if total_weight == zero {
- return Err(WeightedError::AllWeightsZero);
- }
- let distr = X::Sampler::new(zero, total_weight.clone());
-
- Ok(WeightedIndex { cumulative_weights: weights, total_weight, weight_distribution: distr })
- }
-
- /// 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.
- pub fn update_weights(&mut self, new_weights: &[(usize, &X)]) -> Result<(), WeightedError>
- where X: for<'a> ::core::ops::AddAssign<&'a X> +
- for<'a> ::core::ops::SubAssign<&'a X> +
- Clone +
- Default {
- if new_weights.is_empty() {
- return Ok(());
- }
-
- let zero = <X as Default>::default();
-
- let mut total_weight = self.total_weight.clone();
-
- // Check for errors first, so we don't modify `self` in case something
- // goes wrong.
- let mut prev_i = None;
- for &(i, w) in new_weights {
- if let Some(old_i) = prev_i {
- if old_i >= i {
- return Err(WeightedError::InvalidWeight);
- }
- }
- if *w < zero {
- return Err(WeightedError::InvalidWeight);
- }
- if i >= self.cumulative_weights.len() + 1 {
- return Err(WeightedError::TooMany);
- }
-
- let mut old_w = if i < self.cumulative_weights.len() {
- self.cumulative_weights[i].clone()
- } else {
- self.total_weight.clone()
- };
- if i > 0 {
- old_w -= &self.cumulative_weights[i - 1];
- }
-
- total_weight -= &old_w;
- total_weight += w;
- prev_i = Some(i);
- }
- if total_weight == zero {
- return Err(WeightedError::AllWeightsZero);
- }
-
- // Update the weights. Because we checked all the preconditions in the
- // previous loop, this should never panic.
- let mut iter = new_weights.iter();
-
- let mut prev_weight = zero.clone();
- let mut next_new_weight = iter.next();
- let &(first_new_index, _) = next_new_weight.unwrap();
- let mut cumulative_weight = if first_new_index > 0 {
- self.cumulative_weights[first_new_index - 1].clone()
- } else {
- zero.clone()
- };
- for i in first_new_index..self.cumulative_weights.len() {
- match next_new_weight {
- Some(&(j, w)) if i == j => {
- cumulative_weight += w;
- next_new_weight = iter.next();
- },
- _ => {
- let mut tmp = self.cumulative_weights[i].clone();
- tmp -= &prev_weight; // We know this is positive.
- cumulative_weight += &tmp;
- }
- }
- prev_weight = cumulative_weight.clone();
- core::mem::swap(&mut prev_weight, &mut self.cumulative_weights[i]);
- }
-
- self.total_weight = total_weight;
- self.weight_distribution = X::Sampler::new(zero, self.total_weight.clone());
-
- Ok(())
- }
-}
-
-impl<X> Distribution<usize> for WeightedIndex<X> where
- X: SampleUniform + PartialOrd {
- fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
- use ::core::cmp::Ordering;
- let chosen_weight = self.weight_distribution.sample(rng);
- // Find the first item which has a weight *higher* than the chosen weight.
- self.cumulative_weights.binary_search_by(
- |w| if *w <= chosen_weight { Ordering::Less } else { Ordering::Greater }).unwrap_err()
- }
-}
-
-#[cfg(test)]
-mod test {
- use super::*;
-
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weightedindex() {
- let mut r = crate::test::rng(700);
- const N_REPS: u32 = 5000;
- let weights = [1u32, 2, 3, 0, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7];
- let total_weight = weights.iter().sum::<u32>() as f32;
-
- let verify = |result: [i32; 14]| {
- for (i, count) in result.iter().enumerate() {
- let exp = (weights[i] * N_REPS) as f32 / total_weight;
- let mut err = (*count as f32 - exp).abs();
- if err != 0.0 {
- err /= exp;
- }
- assert!(err <= 0.25);
- }
- };
-
- // WeightedIndex from vec
- let mut chosen = [0i32; 14];
- let distr = WeightedIndex::new(weights.to_vec()).unwrap();
- for _ in 0..N_REPS {
- chosen[distr.sample(&mut r)] += 1;
- }
- verify(chosen);
-
- // WeightedIndex from slice
- chosen = [0i32; 14];
- let distr = WeightedIndex::new(&weights[..]).unwrap();
- for _ in 0..N_REPS {
- chosen[distr.sample(&mut r)] += 1;
- }
- verify(chosen);
-
- // WeightedIndex from iterator
- chosen = [0i32; 14];
- let distr = WeightedIndex::new(weights.iter()).unwrap();
- for _ in 0..N_REPS {
- chosen[distr.sample(&mut r)] += 1;
- }
- verify(chosen);
-
- for _ in 0..5 {
- assert_eq!(WeightedIndex::new(&[0, 1]).unwrap().sample(&mut r), 1);
- assert_eq!(WeightedIndex::new(&[1, 0]).unwrap().sample(&mut r), 0);
- assert_eq!(WeightedIndex::new(&[0, 0, 0, 0, 10, 0]).unwrap().sample(&mut r), 4);
- }
-
- assert_eq!(WeightedIndex::new(&[10][0..0]).unwrap_err(), WeightedError::NoItem);
- assert_eq!(WeightedIndex::new(&[0]).unwrap_err(), WeightedError::AllWeightsZero);
- assert_eq!(WeightedIndex::new(&[10, 20, -1, 30]).unwrap_err(), WeightedError::InvalidWeight);
- assert_eq!(WeightedIndex::new(&[-10, 20, 1, 30]).unwrap_err(), WeightedError::InvalidWeight);
- assert_eq!(WeightedIndex::new(&[-10]).unwrap_err(), WeightedError::InvalidWeight);
- }
-
- #[test]
- fn test_update_weights() {
- let data = [
- (&[10u32, 2, 3, 4][..],
- &[(1, &100), (2, &4)][..], // positive change
- &[10, 100, 4, 4][..]),
- (&[1u32, 2, 3, 0, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7][..],
- &[(2, &1), (5, &1), (13, &100)][..], // negative change and last element
- &[1u32, 2, 1, 0, 5, 1, 7, 1, 2, 3, 4, 5, 6, 100][..]),
- ];
-
- for (weights, update, expected_weights) in data.into_iter() {
- let total_weight = weights.iter().sum::<u32>();
- let mut distr = WeightedIndex::new(weights.to_vec()).unwrap();
- assert_eq!(distr.total_weight, total_weight);
-
- distr.update_weights(update).unwrap();
- let expected_total_weight = expected_weights.iter().sum::<u32>();
- let expected_distr = WeightedIndex::new(expected_weights.to_vec()).unwrap();
- assert_eq!(distr.total_weight, expected_total_weight);
- assert_eq!(distr.total_weight, expected_distr.total_weight);
- assert_eq!(distr.cumulative_weights, expected_distr.cumulative_weights);
- }
- }
-}
-
-/// Error type returned from `WeightedIndex::new`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum WeightedError {
- /// The provided weight collection contains no items.
- NoItem,
-
- /// A weight is either less than zero, greater than the supported maximum or
- /// otherwise invalid.
- InvalidWeight,
-
- /// All items in the provided weight collection are zero.
- AllWeightsZero,
-
- /// Too many weights are provided (length greater than `u32::MAX`)
- TooMany,
-}
-
-impl WeightedError {
- fn msg(&self) -> &str {
- match *self {
- WeightedError::NoItem => "No weights provided.",
- WeightedError::InvalidWeight => "A weight is invalid.",
- WeightedError::AllWeightsZero => "All weights are zero.",
- WeightedError::TooMany => "Too many weights (hit u32::MAX)",
- }
- }
-}
-
-#[cfg(feature="std")]
-impl ::std::error::Error for WeightedError {
- fn description(&self) -> &str {
- self.msg()
- }
- fn cause(&self) -> Option<&dyn (::std::error::Error)> {
- None
- }
-}
-
-impl fmt::Display for WeightedError {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "{}", self.msg())
- }
-}