Fix: filtered_search should update radius when top not empty

cpp/test.cpp

@@ -1098,6 +1098,51 @@ template <typename key_at, typename slot_at> void test_replacing_update() {
     expect_eq(final_search[2].member.key, 44);
 }
 
+/**
+ * Tests the filtered search functionality of the index.
+ */
+void test_filtered_search() {
+    constexpr std::size_t dataset_count = 2048;
+    constexpr std::size_t dimensions = 32;
+    metric_punned_t metric(dimensions, metric_kind_t::cos_k);
+
+    std::random_device rd;
+    std::mt19937 gen(rd());
+    std::uniform_real_distribution<> dis(0.0, 1.0);
+    using vector_of_vectors_t = std::vector<std::vector<float>>;
+
+    vector_of_vectors_t vector_of_vectors(dataset_count);
+    for (auto& vector : vector_of_vectors) {
+        vector.resize(dimensions);
+        std::generate(vector.begin(), vector.end(), [&] { return dis(gen); });
+    }
+
+    index_dense_t index = index_dense_t::make(metric);
+    index.reserve(dataset_count);
+    for (std::size_t idx = 0; idx < dataset_count; ++idx)
+        index.add(idx, vector_of_vectors[idx].data());
+    expect_eq(index.size(), dataset_count);
+
+    {
+        auto predicate = [](index_dense_t::key_t key) { return key != 0; };
+        auto results = index.filtered_search(vector_of_vectors[0].data(), 10, predicate);
+        expect_eq(10, results.size()); // ! Should not contain 0
+        for (std::size_t i = 0; i != results.size(); ++i)
+            expect(0 != results[i].member.key);
+    }
+    {
+        auto predicate = [](index_dense_t::key_t) { return false; };
+        auto results = index.filtered_search(vector_of_vectors[0].data(), 10, predicate);
+        expect_eq(0, results.size()); // ! Should not contain 0
+    }
+    {
+        auto predicate = [](index_dense_t::key_t key) { return key == 10; };
+        auto results = index.filtered_search(vector_of_vectors[0].data(), 10, predicate);
+        expect_eq(1, results.size()); // ! Should not contain 0
+        expect_eq(10, results[0].member.key);
+    }
+}
+
 int main(int, char**) {
     test_uint40();
     test_cosine<float, std::int64_t, uint40_t>(10, 10);
@@ -1174,5 +1219,6 @@ int main(int, char**) {
         test_sets<std::int64_t, slot32_t>(set_size, 20, 30);
     test_strings<std::int64_t, slot32_t>();
 
+    test_filtered_search();
     return 0;
 }

include/usearch/index.hpp

@@ -4178,9 +4178,10 @@ class index_gt {
                     // This can substantially grow our priority queue:
                     next.insert({-successor_dist, successor_slot});
                     if (is_dummy<predicate_at>() ||
-                        predicate(member_cref_t{node_at_(successor_slot).ckey(), successor_slot}))
+                        predicate(member_cref_t{node_at_(successor_slot).ckey(), successor_slot})) {
                         top.insert({successor_dist, successor_slot}, top_limit);
-                    radius = top.top().distance;
+                        radius = top.top().distance;
+                    }
                 }
             }
         }