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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/alias_method.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/alias_method.rs')
-rw-r--r--rand/src/distributions/weighted/alias_method.rs499
1 files changed, 0 insertions, 499 deletions
diff --git a/rand/src/distributions/weighted/alias_method.rs b/rand/src/distributions/weighted/alias_method.rs
deleted file mode 100644
index bdd4ba0..0000000
--- a/rand/src/distributions/weighted/alias_method.rs
+++ /dev/null
@@ -1,499 +0,0 @@
-//! This module contains an implementation of alias method for sampling random
-//! indices with probabilities proportional to a collection of weights.
-
-use super::WeightedError;
-#[cfg(not(feature = "std"))]
-use crate::alloc::vec::Vec;
-#[cfg(not(feature = "std"))]
-use crate::alloc::vec;
-use core::fmt;
-use core::iter::Sum;
-use core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
-use crate::distributions::uniform::SampleUniform;
-use crate::distributions::Distribution;
-use crate::distributions::Uniform;
-use crate::Rng;
-
-/// A distribution using weighted sampling to pick a discretely selected item.
-///
-/// Sampling a [`WeightedIndex<W>`] distribution returns the index of a randomly
-/// selected element from the vector used to create the [`WeightedIndex<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
-/// [`Weight`] exists.
-///
-/// # Performance
-///
-/// Given that `n` is the number of items in the vector used to create an
-/// [`WeightedIndex<W>`], [`WeightedIndex<W>`] 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 [`WeightedIndex<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::distributions::weighted::alias_method::WeightedIndex;
-/// use rand::prelude::*;
-///
-/// let choices = vec!['a', 'b', 'c'];
-/// let weights = vec![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).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);
-/// }
-/// ```
-///
-/// [`WeightedIndex<W>`]: crate::distributions::weighted::alias_method::WeightedIndex
-/// [`Weight`]: crate::distributions::weighted::alias_method::Weight
-/// [`Vec<u32>`]: Vec
-/// [`Uniform<u32>::sample`]: Distribution::sample
-/// [`Uniform<W>::sample`]: Distribution::sample
-pub struct WeightedIndex<W: Weight> {
- aliases: Vec<u32>,
- no_alias_odds: Vec<W>,
- uniform_index: Uniform<u32>,
- uniform_within_weight_sum: Uniform<W>,
-}
-
-impl<W: Weight> WeightedIndex<W> {
- /// Creates a new [`WeightedIndex`].
- ///
- /// 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.
- pub fn new(weights: Vec<W>) -> Result<Self, WeightedError> {
- let n = weights.len();
- if n == 0 {
- return Err(WeightedError::NoItem);
- } else if n > ::core::u32::MAX as usize {
- return Err(WeightedError::TooMany);
- }
- let n = n as u32;
-
- let max_weight_size = W::try_from_u32_lossy(n)
- .map(|n| W::MAX / n)
- .unwrap_or(W::ZERO);
- if !weights
- .iter()
- .all(|&w| W::ZERO <= w && w <= max_weight_size)
- {
- return Err(WeightedError::InvalidWeight);
- }
-
- // The sum of weights will represent 100% of no alias odds.
- let weight_sum = Weight::sum(weights.as_slice());
- // Prevent floating point overflow due to rounding errors.
- let weight_sum = if weight_sum > W::MAX {
- W::MAX
- } else {
- weight_sum
- };
- if weight_sum == W::ZERO {
- return Err(WeightedError::AllWeightsZero);
- }
-
- // `weight_sum` would have been zero if `try_from_lossy` causes an error here.
- let n_converted = W::try_from_u32_lossy(n).unwrap();
-
- let mut no_alias_odds = weights;
- for odds in no_alias_odds.iter_mut() {
- *odds *= n_converted;
- // Prevent floating point overflow due to rounding errors.
- *odds = if *odds > W::MAX { W::MAX } else { *odds };
- }
-
- /// 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.
- struct Aliases {
- aliases: Vec<u32>,
- smalls_head: u32,
- bigs_head: u32,
- }
-
- impl Aliases {
- fn new(size: u32) -> Self {
- Aliases {
- aliases: vec![0; size as usize],
- smalls_head: ::core::u32::MAX,
- bigs_head: ::core::u32::MAX,
- }
- }
-
- fn push_small(&mut self, idx: u32) {
- self.aliases[idx as usize] = self.smalls_head;
- self.smalls_head = idx;
- }
-
- fn push_big(&mut self, idx: u32) {
- self.aliases[idx as usize] = self.bigs_head;
- self.bigs_head = idx;
- }
-
- fn pop_small(&mut self) -> u32 {
- let popped = self.smalls_head;
- self.smalls_head = self.aliases[popped as usize];
- popped
- }
-
- fn pop_big(&mut self) -> u32 {
- let popped = self.bigs_head;
- self.bigs_head = self.aliases[popped as usize];
- popped
- }
-
- fn smalls_is_empty(&self) -> bool {
- self.smalls_head == ::core::u32::MAX
- }
-
- fn bigs_is_empty(&self) -> bool {
- self.bigs_head == ::core::u32::MAX
- }
-
- fn set_alias(&mut self, idx: u32, alias: u32) {
- self.aliases[idx as usize] = alias;
- }
- }
-
- let mut aliases = Aliases::new(n);
-
- // Split indices into those with small weights and those with big weights.
- for (index, &odds) in no_alias_odds.iter().enumerate() {
- if odds < weight_sum {
- aliases.push_small(index as u32);
- } else {
- aliases.push_big(index as u32);
- }
- }
-
- // Build the alias map by finding an alias with big weight for each index with
- // small weight.
- while !aliases.smalls_is_empty() && !aliases.bigs_is_empty() {
- let s = aliases.pop_small();
- let b = aliases.pop_big();
-
- aliases.set_alias(s, b);
- no_alias_odds[b as usize] = no_alias_odds[b as usize]
- - weight_sum
- + no_alias_odds[s as usize];
-
- if no_alias_odds[b as usize] < weight_sum {
- aliases.push_small(b);
- } else {
- aliases.push_big(b);
- }
- }
-
- // The remaining indices should have no alias odds of about 100%. This is due to
- // numeric accuracy. Otherwise they would be exactly 100%.
- while !aliases.smalls_is_empty() {
- no_alias_odds[aliases.pop_small() as usize] = weight_sum;
- }
- while !aliases.bigs_is_empty() {
- no_alias_odds[aliases.pop_big() as usize] = weight_sum;
- }
-
- // Prepare distributions for sampling. Creating them beforehand improves
- // sampling performance.
- let uniform_index = Uniform::new(0, n);
- let uniform_within_weight_sum = Uniform::new(W::ZERO, weight_sum);
-
- Ok(Self {
- aliases: aliases.aliases,
- no_alias_odds,
- uniform_index,
- uniform_within_weight_sum,
- })
- }
-}
-
-impl<W: Weight> Distribution<usize> for WeightedIndex<W> {
- fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
- let candidate = rng.sample(self.uniform_index);
- if rng.sample(&self.uniform_within_weight_sum) < self.no_alias_odds[candidate as usize] {
- candidate as usize
- } else {
- self.aliases[candidate as usize] as usize
- }
- }
-}
-
-impl<W: Weight> fmt::Debug for WeightedIndex<W>
-where
- W: fmt::Debug,
- Uniform<W>: fmt::Debug,
-{
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- f.debug_struct("WeightedIndex")
- .field("aliases", &self.aliases)
- .field("no_alias_odds", &self.no_alias_odds)
- .field("uniform_index", &self.uniform_index)
- .field("uniform_within_weight_sum", &self.uniform_within_weight_sum)
- .finish()
- }
-}
-
-impl<W: Weight> Clone for WeightedIndex<W>
-where
- Uniform<W>: Clone,
-{
- fn clone(&self) -> Self {
- Self {
- aliases: self.aliases.clone(),
- no_alias_odds: self.no_alias_odds.clone(),
- uniform_index: self.uniform_index.clone(),
- uniform_within_weight_sum: self.uniform_within_weight_sum.clone(),
- }
- }
-}
-
-/// Trait that must be implemented for weights, that are used with
-/// [`WeightedIndex`]. Currently no guarantees on the correctness of
-/// [`WeightedIndex`] are given for custom implementations of this trait.
-pub trait Weight:
- Sized
- + Copy
- + SampleUniform
- + PartialOrd
- + Add<Output = Self>
- + AddAssign
- + Sub<Output = Self>
- + SubAssign
- + Mul<Output = Self>
- + MulAssign
- + Div<Output = Self>
- + DivAssign
- + Sum
-{
- /// Maximum number representable by `Self`.
- const MAX: Self;
-
- /// Element of `Self` equivalent to 0.
- const ZERO: Self;
-
- /// 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.
- fn try_from_u32_lossy(n: u32) -> Option<Self>;
-
- /// Sums all values in slice `values`.
- fn sum(values: &[Self]) -> Self {
- values.iter().map(|x| *x).sum()
- }
-}
-
-macro_rules! impl_weight_for_float {
- ($T: ident) => {
- impl Weight for $T {
- const MAX: Self = ::core::$T::MAX;
- const ZERO: Self = 0.0;
-
- fn try_from_u32_lossy(n: u32) -> Option<Self> {
- Some(n as $T)
- }
-
- fn sum(values: &[Self]) -> Self {
- pairwise_sum(values)
- }
- }
- };
-}
-
-/// In comparison to naive accumulation, the pairwise sum algorithm reduces
-/// rounding errors when there are many floating point values.
-fn pairwise_sum<T: Weight>(values: &[T]) -> T {
- if values.len() <= 32 {
- values.iter().map(|x| *x).sum()
- } else {
- let mid = values.len() / 2;
- let (a, b) = values.split_at(mid);
- pairwise_sum(a) + pairwise_sum(b)
- }
-}
-
-macro_rules! impl_weight_for_int {
- ($T: ident) => {
- impl Weight for $T {
- const MAX: Self = ::core::$T::MAX;
- const ZERO: Self = 0;
-
- fn try_from_u32_lossy(n: u32) -> Option<Self> {
- let n_converted = n as Self;
- if n_converted >= Self::ZERO && n_converted as u32 == n {
- Some(n_converted)
- } else {
- None
- }
- }
- }
- };
-}
-
-impl_weight_for_float!(f64);
-impl_weight_for_float!(f32);
-impl_weight_for_int!(usize);
-#[cfg(not(target_os = "emscripten"))]
-impl_weight_for_int!(u128);
-impl_weight_for_int!(u64);
-impl_weight_for_int!(u32);
-impl_weight_for_int!(u16);
-impl_weight_for_int!(u8);
-impl_weight_for_int!(isize);
-#[cfg(not(target_os = "emscripten"))]
-impl_weight_for_int!(i128);
-impl_weight_for_int!(i64);
-impl_weight_for_int!(i32);
-impl_weight_for_int!(i16);
-impl_weight_for_int!(i8);
-
-#[cfg(test)]
-mod test {
- use super::*;
-
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weighted_index_f32() {
- test_weighted_index(f32::into);
-
- // Floating point special cases
- assert_eq!(
- WeightedIndex::new(vec![::core::f32::INFINITY]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- assert_eq!(
- WeightedIndex::new(vec![-0_f32]).unwrap_err(),
- WeightedError::AllWeightsZero
- );
- assert_eq!(
- WeightedIndex::new(vec![-1_f32]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- assert_eq!(
- WeightedIndex::new(vec![-::core::f32::INFINITY]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- assert_eq!(
- WeightedIndex::new(vec![::core::f32::NAN]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- }
-
- #[cfg(not(target_os = "emscripten"))]
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weighted_index_u128() {
- test_weighted_index(|x: u128| x as f64);
- }
-
- #[cfg(all(rustc_1_26, not(target_os = "emscripten")))]
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weighted_index_i128() {
- test_weighted_index(|x: i128| x as f64);
-
- // Signed integer special cases
- assert_eq!(
- WeightedIndex::new(vec![-1_i128]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- assert_eq!(
- WeightedIndex::new(vec![::core::i128::MIN]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- }
-
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weighted_index_u8() {
- test_weighted_index(u8::into);
- }
-
- #[test]
- #[cfg(not(miri))] // Miri is too slow
- fn test_weighted_index_i8() {
- test_weighted_index(i8::into);
-
- // Signed integer special cases
- assert_eq!(
- WeightedIndex::new(vec![-1_i8]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- assert_eq!(
- WeightedIndex::new(vec![::core::i8::MIN]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- }
-
- fn test_weighted_index<W: Weight, F: Fn(W) -> f64>(w_to_f64: F)
- where
- WeightedIndex<W>: fmt::Debug,
- {
- const NUM_WEIGHTS: u32 = 10;
- const ZERO_WEIGHT_INDEX: u32 = 3;
- const NUM_SAMPLES: u32 = 15000;
- let mut rng = crate::test::rng(0x9c9fa0b0580a7031);
-
- let weights = {
- let mut weights = Vec::with_capacity(NUM_WEIGHTS as usize);
- let random_weight_distribution = crate::distributions::Uniform::new_inclusive(
- W::ZERO,
- W::MAX / W::try_from_u32_lossy(NUM_WEIGHTS).unwrap(),
- );
- for _ in 0..NUM_WEIGHTS {
- weights.push(rng.sample(&random_weight_distribution));
- }
- weights[ZERO_WEIGHT_INDEX as usize] = W::ZERO;
- weights
- };
- let weight_sum = weights.iter().map(|w| *w).sum::<W>();
- let expected_counts = weights
- .iter()
- .map(|&w| w_to_f64(w) / w_to_f64(weight_sum) * NUM_SAMPLES as f64)
- .collect::<Vec<f64>>();
- let weight_distribution = WeightedIndex::new(weights).unwrap();
-
- let mut counts = vec![0; NUM_WEIGHTS as usize];
- for _ in 0..NUM_SAMPLES {
- counts[rng.sample(&weight_distribution)] += 1;
- }
-
- assert_eq!(counts[ZERO_WEIGHT_INDEX as usize], 0);
- for (count, expected_count) in counts.into_iter().zip(expected_counts) {
- let difference = (count as f64 - expected_count).abs();
- let max_allowed_difference = NUM_SAMPLES as f64 / NUM_WEIGHTS as f64 * 0.1;
- assert!(difference <= max_allowed_difference);
- }
-
- assert_eq!(
- WeightedIndex::<W>::new(vec![]).unwrap_err(),
- WeightedError::NoItem
- );
- assert_eq!(
- WeightedIndex::new(vec![W::ZERO]).unwrap_err(),
- WeightedError::AllWeightsZero
- );
- assert_eq!(
- WeightedIndex::new(vec![W::MAX, W::MAX]).unwrap_err(),
- WeightedError::InvalidWeight
- );
- }
-}