use the bump allocator for radius, doesn't help much

src/lib.rs

@@ -1,3 +1,5 @@
+#![feature(allocator_api)]
+
 use std::{
     collections::HashMap,
     sync::{Mutex, RwLock},
@@ -156,10 +158,21 @@ impl Spindex2d {
     /// Search within a given `radius` from `point`.
     pub fn radius(&self, point: &Point2d, radius: f64) -> Vec<Point2d> {
         let d2 = radius.powi(2);
-        self.aabb(point, radius * 2.0)
-            .into_iter()
-            .filter(|v| v.distance_squared(point) <= d2)
-            .collect()
+
+        let points = self.aabb(point, radius * 2.0);
+        let mut alloc = self.alloc.lock().unwrap();
+        let neighbors = {
+            let mut neighbors = Vec::new_in(alloc.local());
+            for neighbor in points.into_iter() {
+                if neighbor.distance_squared(point) <= d2 {
+                    neighbors.push(neighbor);
+                }
+            }
+
+            neighbors.to_vec()
+        };
+        alloc.reset();
+        neighbors
     }
 
     /// Search an axis-aligned bounding box whose sides are `span` away from the given point.