Fix heuristic selection candidate sourcing

src/lib.rs

@@ -569,8 +569,9 @@ impl Search {
         self.working.clear();
         // Get input candidates from `self.nearest` and store them in `self.working`.
         // `self.candidates` will represent `W` from the paper's algorithm 4 for now.
-        while let Some(Reverse(candidate)) = self.candidates.pop() {
+        for &candidate in &self.nearest {
             self.working.push(candidate);
+            if params.extend_candidates {
                 for hop in layer.nearest_iter(candidate.pid) {
                     if !self.visited.insert(hop) {
                         continue;
@@ -582,6 +583,7 @@ impl Search {
                     self.working.push(new);
                 }
             }
+        }
 
         self.working.sort_unstable();
         self.nearest.clear();