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Diffstat (limited to 'src/metric/vp.rs')
-rw-r--r-- | src/metric/vp.rs | 137 |
1 files changed, 0 insertions, 137 deletions
diff --git a/src/metric/vp.rs b/src/metric/vp.rs deleted file mode 100644 index d6e05df..0000000 --- a/src/metric/vp.rs +++ /dev/null @@ -1,137 +0,0 @@ -//! [Vantage-point trees](https://en.wikipedia.org/wiki/Vantage-point_tree). - -use super::{Metric, NearestNeighbors, Neighborhood, Ordered}; - -use std::iter::FromIterator; - -/// A node in a VP tree. -#[derive(Debug)] -struct VpNode<T> { - /// The vantage point itself. - item: T, - /// The radius of this node. - radius: f64, - /// The size of the subtree inside the radius. - inside_len: usize, -} - -impl<T: Metric> VpNode<T> { - /// Create a new VpNode. - fn new(item: T) -> Self { - Self { - item, - radius: 0.0, - inside_len: 0, - } - } - - /// Build a VP tree recursively. - fn build(slice: &mut [VpNode<T>]) { - if let Some((node, children)) = slice.split_first_mut() { - let item = &node.item; - children.sort_by_cached_key(|n| Ordered(item.distance(&n.item))); - - let (inside, outside) = children.split_at_mut(children.len() / 2); - if let Some(last) = inside.last() { - node.radius = item.distance(&last.item).into(); - } - node.inside_len = inside.len(); - - Self::build(inside); - Self::build(outside); - } - } - - /// Recursively search for nearest neighbors. - fn recurse<'a, U, N>(slice: &'a [VpNode<T>], neighborhood: &mut N) - where - T: 'a, - U: Metric<&'a T>, - N: Neighborhood<&'a T, U>, - { - let (node, children) = slice.split_first().unwrap(); - let (inside, outside) = children.split_at(node.inside_len); - - let distance = neighborhood.consider(&node.item).into(); - - if distance <= node.radius { - if !inside.is_empty() && neighborhood.contains(distance - node.radius) { - Self::recurse(inside, neighborhood); - } - if !outside.is_empty() && neighborhood.contains(node.radius - distance) { - Self::recurse(outside, neighborhood); - } - } else { - if !outside.is_empty() && neighborhood.contains(node.radius - distance) { - Self::recurse(outside, neighborhood); - } - if !inside.is_empty() && neighborhood.contains(distance - node.radius) { - Self::recurse(inside, neighborhood); - } - } - } -} - -/// A [vantage-point tree](https://en.wikipedia.org/wiki/Vantage-point_tree). -#[derive(Debug)] -pub struct VpTree<T>(Vec<VpNode<T>>); - -impl<T: Metric> FromIterator<T> for VpTree<T> { - fn from_iter<I: IntoIterator<Item = T>>(items: I) -> Self { - let mut nodes: Vec<_> = items.into_iter().map(VpNode::new).collect(); - VpNode::build(nodes.as_mut_slice()); - Self(nodes) - } -} - -impl<T, U> NearestNeighbors<T, U> for VpTree<T> -where - T: Metric, - U: Metric<T>, -{ - fn search<'a, 'b, N>(&'a self, mut neighborhood: N) -> N - where - T: 'a, - U: 'b, - N: Neighborhood<&'a T, &'b U>, - { - if !self.0.is_empty() { - VpNode::recurse(&self.0, &mut neighborhood); - } - - neighborhood - } -} - -/// An iterator that moves values out of a VP tree. -#[derive(Debug)] -pub struct IntoIter<T>(std::vec::IntoIter<VpNode<T>>); - -impl<T> Iterator for IntoIter<T> { - type Item = T; - - fn next(&mut self) -> Option<T> { - self.0.next().map(|n| n.item) - } -} - -impl<T> IntoIterator for VpTree<T> { - type Item = T; - type IntoIter = IntoIter<T>; - - fn into_iter(self) -> Self::IntoIter { - IntoIter(self.0.into_iter()) - } -} - -#[cfg(test)] -mod tests { - use super::*; - - use crate::metric::tests::test_nearest_neighbors; - - #[test] - fn test_vp_tree() { - test_nearest_neighbors(VpTree::from_iter); - } -} |