Fix HNSW crash (#1262)

* fix
Signed-off-by: Nxiaojun.lin <xiaojun.lin@zilliz.com>

* update.
Signed-off-by: Nxiaojun.lin <xiaojun.lin@zilliz.com>

CHANGELOG.md

@@ -22,6 +22,7 @@ Please mark all change in change log and use the issue from GitHub
 - \#1075 - improve error message when page size or offset is illegal
 - \#1082 - check page_size or offset value to avoid float
 - \#1115 - http server support load table into memory
+- \#1211 - Server down caused by searching with index_type: HNSW
 - \#1240 - Update license declaration
 
 ## Feature

core/src/index/knowhere/knowhere/index/vector_index/IndexHNSW.cpp

@@ -77,11 +77,14 @@ IndexHNSW::Search(const DatasetPtr& dataset, const Config& config) {
     auto p_dist = (float*)malloc(dist_size * rows);
 
     using P = std::pair<float, int64_t>;
-    auto compare = [](P v1, P v2) { return v1.first < v2.first; };
+    auto compare = [](P& v1, P& v2) { return v1.first < v2.first; };
 #pragma omp parallel for
     for (unsigned int i = 0; i < rows; ++i) {
         const float* single_query = p_data + i * dim;
         std::vector<std::pair<float, int64_t>> ret = index_->searchKnn(single_query, config->k, compare);
+        while (ret.size() < config->k) {
+            ret.push_back(std::make_pair(-1, -1));
+        }
         std::vector<float> dist;
         std::vector<int64_t> ids;
         std::transform(ret.begin(), ret.end(), std::back_inserter(dist),

core/src/wrapper/ConfAdapter.cpp

@@ -268,8 +268,8 @@ HNSWConfAdapter::Match(const TempMetaConf& metaconf) {
     conf->d = metaconf.dim;
     conf->metric_type = metaconf.metric_type;
 
-    conf->ef = 100;  // ef can be auto-configured by using sample data.
-    conf->M = 16;    // A reasonable range of M is from 5 to 48.
+    conf->ef = 200;  // ef can be auto-configured by using sample data.
+    conf->M = 32;    // A reasonable range of M is from 5 to 48.
     return conf;
 }
 

core/unittest/wrapper/test_wrapper.cpp

@@ -77,18 +77,19 @@ INSTANTIATE_TEST_CASE_P(
     Values(
         //["Index type", "Generator type", "dim", "nb", "nq", "k", "build config", "search config"]
 #ifdef MILVUS_GPU_VERSION
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_GPU, "Default", DIM, NB, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_MIX, "Default", 64, 1000, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_GPU, "Default", DIM, NB, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_MIX, "Default", DIM, NB, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFPQ_MIX, "Default", 64, 1000, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_GPU, "Default", DIM, NB, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_MIX, "Default", 64, 1000, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_GPU, "Default", DIM, NB, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_MIX, "Default", DIM, NB, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFPQ_MIX, "Default", 64, 1000, 10, 10),
     // std::make_tuple(milvus::engine::IndexType::NSG_MIX, "Default", 128, 250000, 10, 10),
 #endif
     // std::make_tuple(milvus::engine::IndexType::SPTAG_KDT_RNT_CPU, "Default", 128, 100, 10, 10),
     // std::make_tuple(milvus::engine::IndexType::SPTAG_BKT_RNT_CPU, "Default", 128, 100, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IDMAP, "Default", 64, 1000, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_CPU, "Default", 64, 1000, 10, 10),
-    std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_CPU, "Default", DIM, NB, 10, 10)));
+	std::make_tuple(milvus::engine::IndexType::HNSW, "Default", 64, 10000, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IDMAP, "Default", 64, 1000, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFFLAT_CPU, "Default", 64, 1000, 10, 10),
+	std::make_tuple(milvus::engine::IndexType::FAISS_IVFSQ8_CPU, "Default", DIM, NB, 10, 10)));
 
 #ifdef MILVUS_GPU_VERSION
 TEST_P(KnowhereWrapperTest, WRAPPER_EXCEPTION_TEST) {