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Diffstat (limited to 'src/metric/forest.rs')
-rw-r--r-- | src/metric/forest.rs | 187 |
1 files changed, 0 insertions, 187 deletions
diff --git a/src/metric/forest.rs b/src/metric/forest.rs deleted file mode 100644 index 887ff12..0000000 --- a/src/metric/forest.rs +++ /dev/null @@ -1,187 +0,0 @@ -//! [Dynamization](https://en.wikipedia.org/wiki/Dynamization) for nearest neighbor search. - -use super::kd::KdTree; -use super::vp::VpTree; -use super::{Metric, NearestNeighbors, Neighborhood}; - -use std::iter::{self, Extend, FromIterator}; - -/// The number of bits dedicated to the flat buffer. -const BUFFER_BITS: usize = 6; -/// The maximum size of the buffer. -const BUFFER_SIZE: usize = 1 << BUFFER_BITS; - -/// A dynamic wrapper for a static nearest neighbor search data structure. -/// -/// This type applies [dynamization](https://en.wikipedia.org/wiki/Dynamization) to an arbitrary -/// nearest neighbor search structure `T`, allowing new items to be added dynamically. -#[derive(Debug)] -pub struct Forest<T: IntoIterator> { - /// A flat buffer used for the first few items, to avoid repeatedly rebuilding small trees. - buffer: Vec<T::Item>, - /// The trees of the forest, with sizes in geometric progression. - trees: Vec<Option<T>>, -} - -impl<T, U> Forest<U> -where - U: FromIterator<T> + IntoIterator<Item = T>, -{ - /// Create a new empty forest. - pub fn new() -> Self { - Self { - buffer: Vec::new(), - trees: Vec::new(), - } - } - - /// Add a new item to the forest. - pub fn push(&mut self, item: T) { - self.extend(iter::once(item)); - } - - /// Get the number of items in the forest. - pub fn len(&self) -> usize { - let mut len = self.buffer.len(); - for (i, slot) in self.trees.iter().enumerate() { - if slot.is_some() { - len += 1 << (i + BUFFER_BITS); - } - } - len - } - - /// Check if this forest is empty. - pub fn is_empty(&self) -> bool { - if !self.buffer.is_empty() { - return false; - } - - self.trees.iter().flatten().next().is_none() - } -} - -impl<T, U> Default for Forest<U> -where - U: FromIterator<T> + IntoIterator<Item = T>, -{ - fn default() -> Self { - Self::new() - } -} - -impl<T, U> Extend<T> for Forest<U> -where - U: FromIterator<T> + IntoIterator<Item = T>, -{ - fn extend<I: IntoIterator<Item = T>>(&mut self, items: I) { - self.buffer.extend(items); - if self.buffer.len() < BUFFER_SIZE { - return; - } - - let len = self.len(); - - for i in 0.. { - let bit = 1 << (i + BUFFER_BITS); - - if bit > len { - break; - } - - if i >= self.trees.len() { - self.trees.push(None); - } - - if len & bit == 0 { - if let Some(tree) = self.trees[i].take() { - self.buffer.extend(tree); - } - } else if self.trees[i].is_none() { - let offset = self.buffer.len() - bit; - self.trees[i] = Some(self.buffer.drain(offset..).collect()); - } - } - - debug_assert!(self.buffer.len() < BUFFER_SIZE); - debug_assert!(self.len() == len); - } -} - -impl<T, U> FromIterator<T> for Forest<U> -where - U: FromIterator<T> + IntoIterator<Item = T>, -{ - fn from_iter<I: IntoIterator<Item = T>>(items: I) -> Self { - let mut forest = Self::new(); - forest.extend(items); - forest - } -} - -impl<T: IntoIterator> IntoIterator for Forest<T> { - type Item = T::Item; - type IntoIter = std::vec::IntoIter<T::Item>; - - fn into_iter(mut self) -> Self::IntoIter { - self.buffer.extend(self.trees.into_iter().flatten().flatten()); - self.buffer.into_iter() - } -} - -impl<T, U, V> NearestNeighbors<T, U> for Forest<V> -where - U: Metric<T>, - V: NearestNeighbors<T, U>, - V: IntoIterator<Item = T>, -{ - fn search<'a, 'b, N>(&'a self, mut neighborhood: N) -> N - where - T: 'a, - U: 'b, - N: Neighborhood<&'a T, &'b U>, - { - for item in &self.buffer { - neighborhood.consider(item); - } - - self.trees - .iter() - .flatten() - .fold(neighborhood, |n, t| t.search(n)) - } -} - -/// A forest of k-d trees. -pub type KdForest<T> = Forest<KdTree<T>>; - -/// A forest of vantage-point trees. -pub type VpForest<T> = Forest<VpTree<T>>; - -#[cfg(test)] -mod tests { - use super::*; - - use crate::metric::tests::test_nearest_neighbors; - use crate::metric::ExhaustiveSearch; - - #[test] - fn test_exhaustive_forest() { - test_nearest_neighbors(Forest::<ExhaustiveSearch<_>>::from_iter); - } - - #[test] - fn test_forest_forest() { - test_nearest_neighbors(Forest::<Forest<ExhaustiveSearch<_>>>::from_iter); - } - - #[test] - fn test_kd_forest() { - test_nearest_neighbors(KdForest::from_iter); - } - - #[test] - fn test_vp_forest() { - test_nearest_neighbors(VpForest::from_iter); - } -} |