diff --git a/internal/core/unittest/test_reduce.cpp b/internal/core/unittest/test_reduce.cpp
index 01fdd17b62..1dfef70e82 100644
--- a/internal/core/unittest/test_reduce.cpp
+++ b/internal/core/unittest/test_reduce.cpp
@@ -24,7 +24,7 @@ using SubSearchResultUniq = std::unique_ptr<SubSearchResult>;
 
 std::default_random_engine e(42);
 
-std::unique_ptr<SubSearchResult>
+SubSearchResultUniq
 GenSubSearchResult(const int64_t nq,
                    const int64_t topk,
                    const knowhere::MetricType &metric_type,
@@ -34,8 +34,8 @@ GenSubSearchResult(const int64_t nq,
     SubSearchResultUniq sub_result = std::make_unique<SubSearchResult>(nq, topk, metric_type, round_decimal);
     std::vector<int64_t> ids;
     std::vector<float> distances;
-    for (int n = 0; n < nq; ++n) {
-        for (int k = 0; k < topk; ++k) {
+    for (auto n = 0; n < nq; ++n) {
+        for (auto k = 0; k < topk; ++k) {
             auto gen_x = e() % limit;
             ids.push_back(gen_x);
             distances.push_back(gen_x);
@@ -57,7 +57,7 @@ template<class queue_type>
 void
 CheckSubSearchResult(const int64_t nq,
                      const int64_t topk,
-                     SubSearchResult& search_result,
+                     SubSearchResult& result,
                      std::vector<queue_type>& result_ref) {
     ASSERT_EQ(result_ref.size(), nq);
     for (int n = 0; n < nq; ++n) {
@@ -66,8 +66,8 @@ CheckSubSearchResult(const int64_t nq,
             auto ref_x = result_ref[n].top();
             result_ref[n].pop();
             auto index = n * topk + topk - 1 - k;
-            auto id = search_result.get_seg_offsets()[index];
-            auto distance = search_result.get_distances()[index];
+            auto id = result.get_seg_offsets()[index];
+            auto distance = result.get_distances()[index];
             ASSERT_EQ(id, ref_x);
             ASSERT_EQ(distance, ref_x);
         }
@@ -76,19 +76,19 @@ CheckSubSearchResult(const int64_t nq,
 
 template<class queue_type>
 void
-TestSubSearchResultMerge(const knowhere::MetricType& metric_type) {
-    int64_t num_queries = 16;
-    int64_t topk = 10;
-    int64_t iteration = 10;
-    int64_t round_decimal = 3;
+TestSubSearchResultMerge(const knowhere::MetricType& metric_type,
+                         const int64_t iteration,
+                         const int64_t nq,
+                         const int64_t topk) {
+    const int64_t round_decimal = 3;
 
-    std::vector<queue_type> result_ref(num_queries);
+    std::vector<queue_type> result_ref(nq);
 
-    SubSearchResult final_result(num_queries, topk, metric_type, round_decimal);
+    SubSearchResult final_result(nq, topk, metric_type, round_decimal);
     for (int i = 0; i < iteration; ++i) {
-        SubSearchResultUniq sub_result = GenSubSearchResult(num_queries, topk, metric_type, round_decimal);
+        SubSearchResultUniq sub_result = GenSubSearchResult(nq, topk, metric_type, round_decimal);
         auto ids = sub_result->get_ids();
-        for (int n = 0; n < num_queries; ++n) {
+        for (int n = 0; n < nq; ++n) {
             for (int k = 0; k < topk; ++k) {
                 int64_t x = ids[n * topk + k];
                 result_ref[n].push(x);
@@ -99,12 +99,28 @@ TestSubSearchResultMerge(const knowhere::MetricType& metric_type) {
         }
         final_result.merge(*sub_result);
     }
-    CheckSubSearchResult<queue_type>(num_queries, topk, final_result, result_ref);
+    CheckSubSearchResult<queue_type>(nq, topk, final_result, result_ref);
 }
 
 TEST(Reduce, SubSearchResult) {
     using queue_type_l2 = std::priority_queue<int64_t, std::vector<int64_t>, std::less<int64_t>>;
     using queue_type_ip = std::priority_queue<int64_t, std::vector<int64_t>, std::greater<int64_t>>;
-    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2);
-    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP);
+
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 1, 1, 1);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 1, 1, 10);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 1, 16, 1);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 1, 16, 10);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 4, 1, 1);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 4, 1, 10);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 4, 16, 1);
+    TestSubSearchResultMerge<queue_type_l2>(knowhere::metric::L2, 4, 16, 10);
+
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 1, 1, 1);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 1, 1, 10);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 1, 16, 1);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 1, 16, 10);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 4, 1, 1);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 4, 1, 10);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 4, 16, 1);
+    TestSubSearchResultMerge<queue_type_ip>(knowhere::metric::IP, 4, 16, 10);
 }
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