Use the acap nearest neighbors implementationHEADmaster

5 files changed, 0 insertions, 971 deletions

diff --git a/src/metric/approx.rs b/src/metric/approx.rs
deleted file mode 100644
index c23f9c7..0000000
--- a/src/metric/approx.rs
+++ /dev/null
@@ -1,131 +0,0 @@
-//! [Approximate nearest neighbor search](https://en.wikipedia.org/wiki/Nearest_neighbor_search#Approximate_nearest_neighbor).
-
-use super::{Metric, NearestNeighbors, Neighborhood};
-
-/// An approximate [Neighborhood], for approximate nearest neighbor searches.
-#[derive(Debug)]
-struct ApproximateNeighborhood<N> {
-    inner: N,
-    ratio: f64,
-    limit: usize,
-}
-
-impl<N> ApproximateNeighborhood<N> {
-    fn new(inner: N, ratio: f64, limit: usize) -> Self {
-        Self {
-            inner,
-            ratio,
-            limit,
-        }
-    }
-}
-
-impl<T, U, N> Neighborhood<T, U> for ApproximateNeighborhood<N>
-where
-    U: Metric<T>,
-    N: Neighborhood<T, U>,
-{
-    fn target(&self) -> U {
-        self.inner.target()
-    }
-
-    fn contains(&self, distance: f64) -> bool {
-        if self.limit > 0 {
-            self.inner.contains(self.ratio * distance)
-        } else {
-            false
-        }
-    }
-
-    fn contains_distance(&self, distance: U::Distance) -> bool {
-        self.contains(self.ratio * distance.into())
-    }
-
-    fn consider(&mut self, item: T) -> U::Distance {
-        self.limit = self.limit.saturating_sub(1);
-        self.inner.consider(item)
-    }
-}
-
-/// An [approximate nearest neighbor search](https://en.wikipedia.org/wiki/Nearest_neighbor_search#Approximate_nearest_neighbor)
-/// index.
-///
-/// This wrapper converts an exact nearest neighbor search algorithm into an approximate one by
-/// modifying the behavior of [Neighborhood::contains].  The approximation is controlled by two
-/// parameters:
-///
-/// * `ratio`: The [nearest neighbor distance ratio](https://en.wikipedia.org/wiki/Nearest_neighbor_search#Nearest_neighbor_distance_ratio),
-///   which controls how much closer new candidates must be to be considered.  For example, a ratio
-///   of 2.0 means that a neighbor must be less than half of the current threshold away to be
-///   considered.  A ratio of 1.0 means an exact search.
-///
-/// * `limit`: A limit on the number of candidates to consider.  Typical nearest neighbor algorithms
-///   find a close match quickly, so setting a limit bounds the worst-case search time while keeping
-///   good accuracy.
-#[derive(Debug)]
-pub struct ApproximateSearch<T> {
-    inner: T,
-    ratio: f64,
-    limit: usize,
-}
-
-impl<T> ApproximateSearch<T> {
-    /// Create a new ApproximateSearch index.
-    ///
-    /// * `inner`: The [NearestNeighbors] implementation to wrap.
-    /// * `ratio`: The nearest neighbor distance ratio.
-    /// * `limit`: The maximum number of results to consider.
-    pub fn new(inner: T, ratio: f64, limit: usize) -> Self {
-        Self {
-            inner,
-            ratio,
-            limit,
-        }
-    }
-}
-
-impl<T, U, V> NearestNeighbors<T, U> for ApproximateSearch<V>
-where
-    U: Metric<T>,
-    V: NearestNeighbors<T, U>,
-{
-    fn search<'a, 'b, N>(&'a self, neighborhood: N) -> N
-    where
-        T: 'a,
-        U: 'b,
-        N: Neighborhood<&'a T, &'b U>,
-    {
-        self.inner
-            .search(ApproximateNeighborhood::new(
-                neighborhood,
-                self.ratio,
-                self.limit,
-            ))
-            .inner
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    use crate::metric::kd::KdTree;
-    use crate::metric::tests::test_nearest_neighbors;
-    use crate::metric::vp::VpTree;
-
-    use std::iter::FromIterator;
-
-    #[test]
-    fn test_approx_kd_tree() {
-        test_nearest_neighbors(|iter| {
-            ApproximateSearch::new(KdTree::from_iter(iter), 1.0, std::usize::MAX)
-        });
-    }
-
-    #[test]
-    fn test_approx_vp_tree() {
-        test_nearest_neighbors(|iter| {
-            ApproximateSearch::new(VpTree::from_iter(iter), 1.0, std::usize::MAX)
-        });
-    }
-}
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);
-    }
-}
diff --git a/src/metric/kd.rs b/src/metric/kd.rs
deleted file mode 100644
index 6ea3809..0000000
--- a/src/metric/kd.rs
+++ /dev/null
@@ -1,224 +0,0 @@
-//! [k-d trees](https://en.wikipedia.org/wiki/K-d_tree).
-
-use super::{Metric, NearestNeighbors, Neighborhood, Ordered};
-
-use std::iter::FromIterator;
-
-/// A point in Cartesian space.
-pub trait Cartesian: Metric<[f64]> {
-    /// Returns the number of dimensions necessary to describe this point.
-    fn dimensions(&self) -> usize;
-
-    /// Returns the value of the `i`th coordinate of this point (`i < self.dimensions()`).
-    fn coordinate(&self, i: usize) -> f64;
-}
-
-/// Blanket [Cartesian] implementation for references.
-impl<'a, T: Cartesian> Cartesian for &'a T {
-    fn dimensions(&self) -> usize {
-        (*self).dimensions()
-    }
-
-    fn coordinate(&self, i: usize) -> f64 {
-        (*self).coordinate(i)
-    }
-}
-
-/// Blanket [Metric<[f64]>](Metric) implementation for [Cartesian] references.
-impl<'a, T: Cartesian> Metric<[f64]> for &'a T {
-    type Distance = T::Distance;
-
-    fn distance(&self, other: &[f64]) -> Self::Distance {
-        (*self).distance(other)
-    }
-}
-
-/// Standard cartesian space.
-impl Cartesian for [f64] {
-    fn dimensions(&self) -> usize {
-        self.len()
-    }
-
-    fn coordinate(&self, i: usize) -> f64 {
-        self[i]
-    }
-}
-
-/// Marker trait for cartesian metric spaces.
-pub trait CartesianMetric<T: ?Sized = Self>:
-    Cartesian + Metric<T, Distance = <Self as Metric<[f64]>>::Distance>
-{
-}
-
-/// Blanket [CartesianMetric] implementation for cartesian spaces with compatible metric distance
-/// types.
-impl<T, U> CartesianMetric<T> for U
-where
-    T: ?Sized,
-    U: ?Sized + Cartesian + Metric<T, Distance = <U as Metric<[f64]>>::Distance>,
-{
-}
-
-/// A node in a k-d tree.
-#[derive(Debug)]
-struct KdNode<T> {
-    /// The value stored in this node.
-    item: T,
-    /// The size of the left subtree.
-    left_len: usize,
-}
-
-impl<T: Cartesian> KdNode<T> {
-    /// Create a new KdNode.
-    fn new(item: T) -> Self {
-        Self { item, left_len: 0 }
-    }
-
-    /// Build a k-d tree recursively.
-    fn build(slice: &mut [KdNode<T>], i: usize) {
-        if slice.is_empty() {
-            return;
-        }
-
-        slice.sort_unstable_by_key(|n| Ordered(n.item.coordinate(i)));
-
-        let mid = slice.len() / 2;
-        slice.swap(0, mid);
-
-        let (node, children) = slice.split_first_mut().unwrap();
-        let (left, right) = children.split_at_mut(mid);
-        node.left_len = left.len();
-
-        let j = (i + 1) % node.item.dimensions();
-        Self::build(left, j);
-        Self::build(right, j);
-    }
-
-    /// Recursively search for nearest neighbors.
-    fn recurse<'a, U, N>(
-        slice: &'a [KdNode<T>],
-        i: usize,
-        closest: &mut [f64],
-        neighborhood: &mut N,
-    ) where
-        T: 'a,
-        U: CartesianMetric<&'a T>,
-        N: Neighborhood<&'a T, U>,
-    {
-        let (node, children) = slice.split_first().unwrap();
-        neighborhood.consider(&node.item);
-
-        let target = neighborhood.target();
-        let ti = target.coordinate(i);
-        let ni = node.item.coordinate(i);
-        let j = (i + 1) % node.item.dimensions();
-
-        let (left, right) = children.split_at(node.left_len);
-        let (near, far) = if ti <= ni {
-            (left, right)
-        } else {
-            (right, left)
-        };
-
-        if !near.is_empty() {
-            Self::recurse(near, j, closest, neighborhood);
-        }
-
-        if !far.is_empty() {
-            let saved = closest[i];
-            closest[i] = ni;
-            if neighborhood.contains_distance(target.distance(closest)) {
-                Self::recurse(far, j, closest, neighborhood);
-            }
-            closest[i] = saved;
-        }
-    }
-}
-
-/// A [k-d tree](https://en.wikipedia.org/wiki/K-d_tree).
-#[derive(Debug)]
-pub struct KdTree<T>(Vec<KdNode<T>>);
-
-impl<T: Cartesian> FromIterator<T> for KdTree<T> {
-    /// Create a new k-d tree from a set of points.
-    fn from_iter<I: IntoIterator<Item = T>>(items: I) -> Self {
-        let mut nodes: Vec<_> = items.into_iter().map(KdNode::new).collect();
-        KdNode::build(nodes.as_mut_slice(), 0);
-        Self(nodes)
-    }
-}
-
-impl<T, U> NearestNeighbors<T, U> for KdTree<T>
-where
-    T: Cartesian,
-    U: CartesianMetric<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() {
-            let target = neighborhood.target();
-            let dims = target.dimensions();
-            let mut closest: Vec<_> = (0..dims).map(|i| target.coordinate(i)).collect();
-
-            KdNode::recurse(&self.0, 0, &mut closest, &mut neighborhood);
-        }
-
-        neighborhood
-    }
-}
-
-/// An iterator that the moves values out of a k-d tree.
-#[derive(Debug)]
-pub struct IntoIter<T>(std::vec::IntoIter<KdNode<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 KdTree<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, Point};
-    use crate::metric::SquaredDistance;
-
-    impl Metric<[f64]> for Point {
-        type Distance = SquaredDistance;
-
-        fn distance(&self, other: &[f64]) -> Self::Distance {
-            self.0.distance(other)
-        }
-    }
-
-    impl Cartesian for Point {
-        fn dimensions(&self) -> usize {
-            self.0.dimensions()
-        }
-
-        fn coordinate(&self, i: usize) -> f64 {
-            self.0.coordinate(i)
-        }
-    }
-
-    #[test]
-    fn test_kd_tree() {
-        test_nearest_neighbors(KdTree::from_iter);
-    }
-}
diff --git a/src/metric/soft.rs b/src/metric/soft.rs
deleted file mode 100644
index d443bfd..0000000
--- a/src/metric/soft.rs
+++ /dev/null
@@ -1,292 +0,0 @@
-//! [Soft deletion](https://en.wiktionary.org/wiki/soft_deletion) for nearest neighbor search.
-
-use super::forest::{KdForest, VpForest};
-use super::kd::KdTree;
-use super::vp::VpTree;
-use super::{Metric, NearestNeighbors, Neighborhood};
-
-use std::iter;
-use std::iter::FromIterator;
-use std::mem;
-
-/// A trait for objects that can be soft-deleted.
-pub trait SoftDelete {
-    /// Check whether this item is deleted.
-    fn is_deleted(&self) -> bool;
-}
-
-/// Blanket [SoftDelete] implementation for references.
-impl<'a, T: SoftDelete> SoftDelete for &'a T {
-    fn is_deleted(&self) -> bool {
-        (*self).is_deleted()
-    }
-}
-
-/// [Neighborhood] wrapper that ignores soft-deleted items.
-#[derive(Debug)]
-struct SoftNeighborhood<N>(N);
-
-impl<T, U, N> Neighborhood<T, U> for SoftNeighborhood<N>
-where
-    T: SoftDelete,
-    U: Metric<T>,
-    N: Neighborhood<T, U>,
-{
-    fn target(&self) -> U {
-        self.0.target()
-    }
-
-    fn contains(&self, distance: f64) -> bool {
-        self.0.contains(distance)
-    }
-
-    fn contains_distance(&self, distance: U::Distance) -> bool {
-        self.0.contains_distance(distance)
-    }
-
-    fn consider(&mut self, item: T) -> U::Distance {
-        if item.is_deleted() {
-            self.target().distance(&item)
-        } else {
-            self.0.consider(item)
-        }
-    }
-}
-
-/// A [NearestNeighbors] implementation that supports [soft deletes](https://en.wiktionary.org/wiki/soft_deletion).
-#[derive(Debug)]
-pub struct SoftSearch<T>(T);
-
-impl<T, U> SoftSearch<U>
-where
-    T: SoftDelete,
-    U: FromIterator<T> + IntoIterator<Item = T>,
-{
-    /// Create a new empty soft index.
-    pub fn new() -> Self {
-        Self(iter::empty().collect())
-    }
-
-    /// Push a new item into this index.
-    pub fn push(&mut self, item: T)
-    where
-        U: Extend<T>,
-    {
-        self.0.extend(iter::once(item));
-    }
-
-    /// Rebuild this index, discarding deleted items.
-    pub fn rebuild(&mut self) {
-        let items = mem::replace(&mut self.0, iter::empty().collect());
-        self.0 = items.into_iter().filter(|e| !e.is_deleted()).collect();
-    }
-}
-
-impl<T, U> Default for SoftSearch<U>
-where
-    T: SoftDelete,
-    U: FromIterator<T> + IntoIterator<Item = T>,
-{
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-impl<T, U: Extend<T>> Extend<T> for SoftSearch<U> {
-    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
-        self.0.extend(iter);
-    }
-}
-
-impl<T, U: FromIterator<T>> FromIterator<T> for SoftSearch<U> {
-    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
-        Self(U::from_iter(iter))
-    }
-}
-
-impl<T: IntoIterator> IntoIterator for SoftSearch<T> {
-    type Item = T::Item;
-    type IntoIter = T::IntoIter;
-
-    fn into_iter(self) -> Self::IntoIter {
-        self.0.into_iter()
-    }
-}
-
-impl<T, U, V> NearestNeighbors<T, U> for SoftSearch<V>
-where
-    T: SoftDelete,
-    U: Metric<T>,
-    V: NearestNeighbors<T, U>,
-{
-    fn search<'a, 'b, N>(&'a self, neighborhood: N) -> N
-    where
-        T: 'a,
-        U: 'b,
-        N: Neighborhood<&'a T, &'b U>,
-    {
-        self.0.search(SoftNeighborhood(neighborhood)).0
-    }
-}
-
-/// A k-d forest that supports soft deletes.
-pub type SoftKdForest<T> = SoftSearch<KdForest<T>>;
-
-/// A k-d tree that supports soft deletes.
-pub type SoftKdTree<T> = SoftSearch<KdTree<T>>;
-
-/// A VP forest that supports soft deletes.
-pub type SoftVpForest<T> = SoftSearch<VpForest<T>>;
-
-/// A VP tree that supports soft deletes.
-pub type SoftVpTree<T> = SoftSearch<VpTree<T>>;
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    use crate::metric::kd::Cartesian;
-    use crate::metric::tests::Point;
-    use crate::metric::Neighbor;
-
-    #[derive(Debug, PartialEq)]
-    struct SoftPoint {
-        point: Point,
-        deleted: bool,
-    }
-
-    impl SoftPoint {
-        fn new(x: f64, y: f64, z: f64) -> Self {
-            Self {
-                point: Point([x, y, z]),
-                deleted: false,
-            }
-        }
-
-        fn deleted(x: f64, y: f64, z: f64) -> Self {
-            Self {
-                point: Point([x, y, z]),
-                deleted: true,
-            }
-        }
-    }
-
-    impl SoftDelete for SoftPoint {
-        fn is_deleted(&self) -> bool {
-            self.deleted
-        }
-    }
-
-    impl Metric for SoftPoint {
-        type Distance = <Point as Metric>::Distance;
-
-        fn distance(&self, other: &Self) -> Self::Distance {
-            self.point.distance(&other.point)
-        }
-    }
-
-    impl Metric<[f64]> for SoftPoint {
-        type Distance = <Point as Metric>::Distance;
-
-        fn distance(&self, other: &[f64]) -> Self::Distance {
-            self.point.distance(other)
-        }
-    }
-
-    impl Cartesian for SoftPoint {
-        fn dimensions(&self) -> usize {
-            self.point.dimensions()
-        }
-
-        fn coordinate(&self, i: usize) -> f64 {
-            self.point.coordinate(i)
-        }
-    }
-
-    impl Metric<SoftPoint> for Point {
-        type Distance = <Point as Metric>::Distance;
-
-        fn distance(&self, other: &SoftPoint) -> Self::Distance {
-            self.distance(&other.point)
-        }
-    }
-
-    fn test_index<T>(index: &T)
-    where
-        T: NearestNeighbors<SoftPoint, Point>,
-    {
-        let target = Point([0.0, 0.0, 0.0]);
-
-        assert_eq!(
-            index.nearest(&target),
-            Some(Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0))
-        );
-
-        assert_eq!(index.nearest_within(&target, 2.0), None);
-        assert_eq!(
-            index.nearest_within(&target, 4.0),
-            Some(Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0))
-        );
-
-        assert_eq!(
-            index.k_nearest(&target, 3),
-            vec![
-                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
-                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
-                Neighbor::new(&SoftPoint::new(2.0, 3.0, 6.0), 7.0),
-            ]
-        );
-
-        assert_eq!(
-            index.k_nearest_within(&target, 3, 6.0),
-            vec![
-                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
-                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
-            ]
-        );
-        assert_eq!(
-            index.k_nearest_within(&target, 3, 8.0),
-            vec![
-                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
-                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
-                Neighbor::new(&SoftPoint::new(2.0, 3.0, 6.0), 7.0),
-            ]
-        );
-    }
-
-    fn test_soft_index<T>(index: &mut SoftSearch<T>)
-    where
-        T: Extend<SoftPoint>,
-        T: FromIterator<SoftPoint>,
-        T: IntoIterator<Item = SoftPoint>,
-        T: NearestNeighbors<SoftPoint, Point>,
-    {
-        let points = vec![
-            SoftPoint::deleted(0.0, 0.0, 0.0),
-            SoftPoint::new(3.0, 4.0, 0.0),
-            SoftPoint::new(5.0, 0.0, 12.0),
-            SoftPoint::new(0.0, 8.0, 15.0),
-            SoftPoint::new(1.0, 2.0, 2.0),
-            SoftPoint::new(2.0, 3.0, 6.0),
-            SoftPoint::new(4.0, 4.0, 7.0),
-        ];
-
-        for point in points {
-            index.push(point);
-        }
-        test_index(index);
-
-        index.rebuild();
-        test_index(index);
-    }
-
-    #[test]
-    fn test_soft_kd_forest() {
-        test_soft_index(&mut SoftKdForest::new());
-    }
-
-    #[test]
-    fn test_soft_vp_forest() {
-        test_soft_index(&mut SoftVpForest::new());
-    }
-}
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);
-    }
-}