fix seen of searcher not been clear when lower_search

Author: miamia0

src/hnsw/hnsw_const.rs

@@ -385,12 +385,14 @@ where
         // See Algorithm 5 line 5 of the paper. The paper makes no further comment on why `1` was chosen.
         let &Neighbor { index, distance } = searcher.nearest.first().unwrap();
         searcher.nearest.clear();
+        searcher.seen.clear();
         // Update the node to the next layer.
         let new_index = layer[index].next_node as usize;
         let candidate = Neighbor {
             index: new_index,
             distance,
         };
+        searcher.seen.insert(layer[index].zero_node);
         // Insert the index of the nearest neighbor into the nearest pool for the next layer.
         searcher.nearest.push(candidate);
         // Insert the index into the candidate pool as well.

tests/simple.rs

@@ -1,6 +1,7 @@
 //! Useful tests for debugging since they are hand-written and easy to see the debugging output.
 
 use hnsw::{Hnsw, Searcher};
+use itertools::Itertools;
 use rand_pcg::Pcg64;
 use space::{Metric, Neighbor};
 
@@ -18,13 +19,43 @@ impl Metric<&[f64]> for Euclidean {
     }
 }
 
+struct TestBruteForceHelper {
+    vectors: Vec<(usize, Vec<f64>)>,
+}
+
+impl TestBruteForceHelper {
+    fn new() -> Self {
+        Self {
+            vectors: Vec::new(),
+        }
+    }
+
+    fn push(&mut self, v: (usize, Vec<f64>)) {
+        self.vectors.push(v);
+    }
+
+    fn search(&self, query: &[f64], top_k: usize) -> Vec<usize> {
+        let metric = Euclidean;
+        let mut candidates: Vec<(usize, u64)> = self
+            .vectors
+            .iter()
+            .map(|v| (v.0.clone(), metric.distance(&query, &v.1.as_slice())))
+            .collect_vec();
+
+        candidates.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap_or(std::cmp::Ordering::Equal));
+
+        candidates.into_iter().take(top_k).map(|v| v.0).collect()
+    }
+}
+
 fn test_hnsw() -> (
     Hnsw<Euclidean, &'static [f64], Pcg64, 12, 24>,
     Searcher<u64>,
+    TestBruteForceHelper,
 ) {
     let mut searcher = Searcher::default();
     let mut hnsw = Hnsw::new(Euclidean);
-
+    let mut helper = TestBruteForceHelper::new();
     let features = [
         &[0.0, 0.0, 0.0, 1.0],
         &[0.0, 0.0, 1.0, 0.0],
@@ -36,11 +67,12 @@ fn test_hnsw() -> (
         &[1.0, 0.0, 0.0, 1.0],
     ];
 
-    for &feature in &features {
-        hnsw.insert(feature, &mut searcher);
+    for (index, feature) in features.iter().enumerate() {
+        helper.push((index, feature.to_vec()));
+        hnsw.insert(*feature, &mut searcher);
     }
 
-    (hnsw, searcher)
+    (hnsw, searcher, helper)
 }
 
 #[test]
@@ -50,7 +82,7 @@ fn insertion() {
 
 #[test]
 fn nearest_neighbor() {
-    let (hnsw, mut searcher) = test_hnsw();
+    let (hnsw, mut searcher, helper) = test_hnsw();
     let searcher = &mut searcher;
     let mut neighbors = [Neighbor {
         index: !0,
@@ -101,4 +133,17 @@ fn nearest_neighbor() {
             }
         ]
     );
+    // test for not panicking
+    for topk in 0..8 {
+        let mut neighbors = vec![
+            Neighbor {
+                index: !0,
+                distance: !0,
+            };
+            topk
+        ];
+        hnsw.nearest(&&[0.0, 0.0, 0.0, 1.0][..], 24, searcher, &mut neighbors);
+        let result = neighbors.iter().map(|item| item.index).collect_vec();
+        assert_eq!(result, helper.search(&[0.0, 0.0, 0.0, 1.0], topk));
+    }
 }