Add more extensive randomized test

tests/all.rs

@@ -1,4 +1,8 @@
-use instant_distance::{Hnsw, PointId, Search};
+use ordered_float::OrderedFloat;
+use rand::rngs::{StdRng, ThreadRng};
+use rand::{Rng, SeedableRng};
+
+use instant_distance::{Hnsw, Point as _, PointId, Search};
 
 #[test]
 fn basic() {
@@ -17,6 +21,51 @@ fn basic() {
     assert_eq!(&results, &[pids[0]]);
 }
 
+#[test]
+fn randomized() {
+    let seed = ThreadRng::default().gen::<u64>();
+    println!("seed {}", seed);
+
+    let mut rng = StdRng::seed_from_u64(seed);
+    let points = (0..1024)
+        .into_iter()
+        .map(|_| Point(rng.gen(), rng.gen()))
+        .collect::<Vec<_>>();
+
+    let query = Point(rng.gen(), rng.gen());
+    println!("query: {:?}", query);
+
+    for (i, p) in points.iter().enumerate() {
+        println!("{:2} {:?} ({})", i, p, query.distance(p));
+    }
+
+    let (hnsw, pids) = Hnsw::<Point>::builder().seed(seed).build(&points);
+    let mut search = Search::default();
+    let mut results = vec![PointId::default()];
+    let found = hnsw.search(&query, &mut results, &mut search);
+    assert_eq!(found, 1);
+
+    let nearest = points
+        .iter()
+        .enumerate()
+        .map(|(i, other)| (OrderedFloat::from(query.distance(other)), i))
+        .min()
+        .unwrap();
+    println!(
+        "nearest (brute force): {:?} @ {:9.7}",
+        pids[nearest.1],
+        nearest.0.into_inner()
+    );
+
+    let index = pids.iter().position(|p| p == &results[0]).unwrap();
+    println!(
+        "nearest (hnsw):        {:?} @ {:9.7}",
+        results[0],
+        query.distance(&points[index])
+    );
+    assert_eq!(pids[nearest.1], results[0]);
+}
+
 #[derive(Clone, Copy, Debug)]
 struct Point(f32, f32);