Stop condition (#490)

* Add stop condition, multivector search, epsilon search

* Fix include

* Update readme

* Update multivector tests

* One header file

* Add bare_bone_search flag

* Fix epsilon search

* Refactoring

* Adress comments

* Fix assert

* Add ef to multivector search, return vector, refactoring

* Refactoring

* Adress comments

* Add bare bone search comment

Co-authored-by: Yury Malkov <yurymalkov@gmail.com>

* Remove has_deletions flag

---------
Co-authored-by: Yury Malkov <yurymalkov@gmail.com>

.github/workflows/build.yml

@@ -67,10 +67,14 @@ jobs:
           ./example_mt_search
           ./example_mt_filter
           ./example_mt_replace_deleted
+          ./example_multivector_search
+          ./example_epsilon_search
           ./searchKnnCloserFirst_test
           ./searchKnnWithFilter_test
           ./multiThreadLoad_test
           ./multiThread_replace_test
           ./test_updates
           ./test_updates update
+          ./multivector_search_test
+          ./epsilon_search_test
         shell: bash

.gitignore

@@ -10,3 +10,4 @@ var/
 .vscode/
 .vs/
 **.DS_Store
+*.pyc

CMakeLists.txt

@@ -57,6 +57,12 @@ if(HNSWLIB_EXAMPLES)
     add_executable(example_search examples/cpp/example_search.cpp)
     target_link_libraries(example_search hnswlib)
 
+    add_executable(example_epsilon_search examples/cpp/example_epsilon_search.cpp)
+    target_link_libraries(example_epsilon_search hnswlib)
+
+    add_executable(example_multivector_search examples/cpp/example_multivector_search.cpp)
+    target_link_libraries(example_multivector_search hnswlib)
+
     add_executable(example_filter examples/cpp/example_filter.cpp)
     target_link_libraries(example_filter hnswlib)
 
@@ -73,6 +79,12 @@ if(HNSWLIB_EXAMPLES)
     target_link_libraries(example_mt_replace_deleted hnswlib)
 
     # tests
+    add_executable(multivector_search_test tests/cpp/multivector_search_test.cpp)
+    target_link_libraries(multivector_search_test hnswlib)
+
+    add_executable(epsilon_search_test tests/cpp/epsilon_search_test.cpp)
+    target_link_libraries(epsilon_search_test hnswlib)
+
     add_executable(test_updates tests/cpp/updates_test.cpp)
     target_link_libraries(test_updates hnswlib)
 

README.md

@@ -229,6 +229,8 @@ print("Recall for two batches:", np.mean(labels.reshape(-1) == np.arange(len(dat
 * filtering during the search with a boolean function
 * deleting the elements and reusing the memory of the deleted elements for newly added elements
 * multithreaded usage
+* multivector search
+* epsilon search
 
 
 ### Bindings installation

examples/cpp/EXAMPLES.md

@@ -182,4 +182,8 @@ int main() {
 Multithreaded examples:
 * Creating index, inserting elements, searching [example_mt_search.cpp](example_mt_search.cpp)
 * Filtering during the search with a boolean function [example_mt_filter.cpp](example_mt_filter.cpp)
-* Reusing the memory of the deleted elements when new elements are being added [example_mt_replace_deleted.cpp](example_mt_replace_deleted.cpp)
+* Reusing the memory of the deleted elements when new elements are being added [example_mt_replace_deleted.cpp](example_mt_replace_deleted.cpp)
+
+More examples:
+* Multivector search [example_multivector_search.cpp](example_multivector_search.cpp)
+* Epsilon search [example_epsilon_search.cpp](example_epsilon_search.cpp)

examples/cpp/example_epsilon_search.cpp

@@ -0,0 +1,66 @@
+#include "../../hnswlib/hnswlib.h"
+
+typedef unsigned int docidtype;
+typedef float dist_t;
+
+int main() {
+    int dim = 16;                  // Dimension of the elements
+    int max_elements = 10000;      // Maximum number of elements, should be known beforehand
+    int M = 16;                    // Tightly connected with internal dimensionality of the data
+                                   // strongly affects the memory consumption
+    int ef_construction = 200;     // Controls index search speed/build speed tradeoff
+    int min_num_candidates = 100;  // Minimum number of candidates to search in the epsilon region
+                                   // this parameter is similar to ef
+
+    int num_queries = 5;
+    float epsilon2 = 2.0;          // Squared distance to query
+
+    // Initing index
+    hnswlib::L2Space space(dim);
+    hnswlib::HierarchicalNSW<dist_t>* alg_hnsw = new hnswlib::HierarchicalNSW<dist_t>(&space, max_elements, M, ef_construction);
+
+    // Generate random data
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib_real;
+
+    size_t data_point_size = space.get_data_size();
+    char* data = new char[data_point_size * max_elements];
+    for (int i = 0; i < max_elements; i++) {
+        char* point_data = data + i * data_point_size;
+        for (int j = 0; j < dim; j++) {
+            char* vec_data = point_data + j * sizeof(float);
+            float value = distrib_real(rng);
+            *(float*)vec_data = value;
+        }
+    }
+
+    // Add data to index
+    for (int i = 0; i < max_elements; i++) {
+        hnswlib::labeltype label = i;
+        char* point_data = data + i * data_point_size;
+        alg_hnsw->addPoint(point_data, label);
+    }
+
+    // Query random vectors
+    for (int i = 0; i < num_queries; i++) {
+        char* query_data = new char[data_point_size];
+        for (int j = 0; j < dim; j++) {
+            size_t offset = j * sizeof(float);
+            char* vec_data = query_data + offset;
+            float value = distrib_real(rng);
+            *(float*)vec_data = value;
+        }
+        std::cout << "Query #" << i << "\n";
+        hnswlib::EpsilonSearchStopCondition<dist_t> stop_condition(epsilon2, min_num_candidates, max_elements);
+        std::vector<std::pair<float, hnswlib::labeltype>> result = 
+            alg_hnsw->searchStopConditionClosest(query_data, stop_condition);
+        size_t num_vectors = result.size();
+        std::cout << "Found " << num_vectors << " vectors\n";
+        delete[] query_data;
+    }
+
+    delete[] data;
+    delete alg_hnsw;
+    return 0;
+}

examples/cpp/example_multivector_search.cpp

@@ -0,0 +1,83 @@
+#include "../../hnswlib/hnswlib.h"
+
+typedef unsigned int docidtype;
+typedef float dist_t;
+
+int main() {
+    int dim = 16;               // Dimension of the elements
+    int max_elements = 10000;   // Maximum number of elements, should be known beforehand
+    int M = 16;                 // Tightly connected with internal dimensionality of the data
+                                // strongly affects the memory consumption
+    int ef_construction = 200;  // Controls index search speed/build speed tradeoff
+
+    int num_queries = 5;
+    int num_docs = 5;           // Number of documents to search
+    int ef_collection = 6;      // Number of candidate documents during the search
+                                // Controlls the recall: higher ef leads to better accuracy, but slower search
+    docidtype min_doc_id = 0;
+    docidtype max_doc_id = 9;
+
+    // Initing index
+    hnswlib::MultiVectorL2Space<docidtype> space(dim);
+    hnswlib::HierarchicalNSW<dist_t>* alg_hnsw = new hnswlib::HierarchicalNSW<dist_t>(&space, max_elements, M, ef_construction);
+
+    // Generate random data
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib_real;
+    std::uniform_int_distribution<docidtype> distrib_docid(min_doc_id, max_doc_id);
+
+    size_t data_point_size = space.get_data_size();
+    char* data = new char[data_point_size * max_elements];
+    for (int i = 0; i < max_elements; i++) {
+        // set vector value
+        char* point_data = data + i * data_point_size;
+        for (int j = 0; j < dim; j++) {
+            char* vec_data = point_data + j * sizeof(float);
+            float value = distrib_real(rng);
+            *(float*)vec_data = value;
+        }
+        // set document id
+        docidtype doc_id = distrib_docid(rng);
+        space.set_doc_id(point_data, doc_id);
+    }
+
+    // Add data to index
+    std::unordered_map<hnswlib::labeltype, docidtype> label_docid_lookup;
+    for (int i = 0; i < max_elements; i++) {
+        hnswlib::labeltype label = i;
+        char* point_data = data + i * data_point_size;
+        alg_hnsw->addPoint(point_data, label);
+        label_docid_lookup[label] = space.get_doc_id(point_data);
+    }
+
+    // Query random vectors
+    size_t query_size = dim * sizeof(float);
+    for (int i = 0; i < num_queries; i++) {
+        char* query_data = new char[query_size];
+        for (int j = 0; j < dim; j++) {
+            size_t offset = j * sizeof(float);
+            char* vec_data = query_data + offset;
+            float value = distrib_real(rng);
+            *(float*)vec_data = value;
+        }
+        std::cout << "Query #" << i << "\n";
+        hnswlib::MultiVectorSearchStopCondition<docidtype, dist_t> stop_condition(space, num_docs, ef_collection);
+        std::vector<std::pair<float, hnswlib::labeltype>> result = 
+            alg_hnsw->searchStopConditionClosest(query_data, stop_condition);
+        size_t num_vectors = result.size();
+
+        std::unordered_map<docidtype, size_t> doc_counter;
+        for (auto pair: result) {
+            hnswlib::labeltype label = pair.second;
+            docidtype doc_id = label_docid_lookup[label];
+            doc_counter[doc_id] += 1;
+        }
+        std::cout << "Found " << doc_counter.size() << " documents, " << num_vectors << " vectors\n";
+        delete[] query_data;
+    }
+
+    delete[] data;
+    delete alg_hnsw;
+    return 0;
+}