[SVS] Add SVS Index TopK benchmark

tests/benchmark/bm_initialization/bm_basics_svs_initialize_fp32.h

@@ -54,3 +54,17 @@ BENCHMARK_REGISTER_F(BM_VecSimSVS, BM_FUNC_NAME(BM_AddVectorsDuringTraining))
                    {2, 4}})
     ->ArgNames({"training_threshold", "thread_count"})
     ->UseRealTime();
+
+// TopK search on the loaded SVS index, using the search window_size and k defined below.
+// {window_size, k} (recall that always window_size >= k)
+BENCHMARK_TEMPLATE_DEFINE_F(BM_VecSimSVS, BM_FUNC_NAME(BM_TopK), DATA_TYPE_INDEX_T)
+(benchmark::State &st) { TopK_SVS(st); }
+BENCHMARK_REGISTER_F(BM_VecSimSVS, BM_FUNC_NAME(BM_TopK))
+    ->Unit(benchmark::kMillisecond)
+    ->Iterations(10)
+    ->Args({10, 10})
+    ->Args({200, 10})
+    ->Args({100, 100})
+    ->Args({200, 100})
+    ->Args({500, 500})
+    ->ArgNames({"window_size", "k"});

tests/benchmark/bm_vecsim_svs.h

@@ -54,6 +54,10 @@ class BM_VecSimSVS : public BM_VecSimGeneral {
     // Deletes an amount of labels from the index that triggers inplace consolidation.
     void RunGC(benchmark::State &st);
 
+    // TopK search benchmark. The search window size and k are provided by the benchmark
+    // registration.
+    void TopK_SVS(benchmark::State &st);
+
 private:
     static const char *svs_index_tar_file;
     static std::string base_path;
@@ -463,6 +467,31 @@ void BM_VecSimSVS<index_type_t>::RunGC(benchmark::State &st) {
     ASSERT_EQ(VecSimIndex_IndexSize(tiered_index), N_VECTORS - num_deletions);
 }
 
+template <typename index_type_t>
+void BM_VecSimSVS<index_type_t>::TopK_SVS(benchmark::State &st) {
+    // Search window size (Vamana graph accuracy/latency tuning) and number of results, as
+    // defined by the benchmark registration.
+    size_t window_size = st.range(0);
+    size_t k = st.range(1);
+
+    // Load the SVS index from file (update_threshold is irrelevant for a search-only benchmark).
+    auto *index = CreateSVSIndexFromFile(1);
+
+    SVSRuntimeParams svs_params = {.windowSize = window_size};
+
+    VecSimQueryParams query_params = {.svsRuntimeParams = svs_params};
+
+    size_t iter = 0;
+    for (auto _ : st) {
+        auto results = VecSimIndex_TopKQuery(index, test_vectors[iter % N_QUERIES].data(), k,
+                                             &query_params, BY_SCORE);
+        VecSimQueryReply_Free(results);
+        iter++;
+    }
+
+    VecSimIndex_Free(index);
+}
+
 #define UNIT_AND_ITERATIONS Unit(benchmark::kMillisecond)->Iterations(2)
 
 #if HAVE_SVS_LVQ