Python API for CAGRA+HNSW

cpp/include/cuvs/neighbors/cagra.h

@@ -267,6 +267,15 @@ cuvsError_t cuvsCagraIndexCreate(cuvsCagraIndex_t* index);
  */
 cuvsError_t cuvsCagraIndexDestroy(cuvsCagraIndex_t index);
 
+/**
+ * @brief Get dimension of the CAGRA index
+ *
+ * @param[in] index CAGRA index
+ * @param[out] dim return dimension of the index
+ * @return cuvsError_t
+ */
+cuvsError_t cuvsCagraIndexGetDims(cuvsCagraIndex_t index, int* dim);
+
 /**
  * @}
  */
@@ -338,7 +347,7 @@ cuvsError_t cuvsCagraBuild(cuvsResources_t res,
  *        with the same type of `queries`, such that `index.dtype.code ==
  * queries.dl_tensor.dtype.code` Types for input are:
  *        1. `queries`:
- *`         a. kDLDataType.code == kDLFloat` and `kDLDataType.bits = 32`
+ *          a. `kDLDataType.code == kDLFloat` and `kDLDataType.bits = 32`
  *          b. `kDLDataType.code == kDLInt` and `kDLDataType.bits = 8`
  *          c. `kDLDataType.code == kDLUInt` and `kDLDataType.bits = 8`
  *        2. `neighbors`: `kDLDataType.code == kDLUInt` and `kDLDataType.bits = 32`

cpp/include/cuvs/neighbors/hnsw.h

@@ -105,8 +105,10 @@ cuvsError_t cuvsHnswIndexDestroy(cuvsHnswIndex_t index);
  *        with the same type of `queries`, such that `index.dtype.code ==
  *        queries.dl_tensor.dtype.code`
  *        Supported types for input are:
- *        1. `queries`: `kDLDataType.code == kDLFloat` or `kDLDataType.code == kDLInt` and
- * `kDLDataType.bits = 32`
+ *        1. `queries`:
+ *          a. `kDLDataType.code == kDLFloat` and `kDLDataType.bits = 32`
+ *          b. `kDLDataType.code == kDLInt` and `kDLDataType.bits = 8`
+ *          c. `kDLDataType.code == kDLUInt` and `kDLDataType.bits = 8`
  *        2. `neighbors`: `kDLDataType.code == kDLUInt` and `kDLDataType.bits = 64`
  *        3. `distances`: `kDLDataType.code == kDLFloat` and `kDLDataType.bits = 32`
  * NOTE: The HNSW index can only be searched by the hnswlib wrapper in cuVS,

cpp/include/cuvs/neighbors/hnsw.hpp

@@ -173,6 +173,8 @@ std::unique_ptr<index<int8_t>> from_cagra(
 
 /**@}*/
 
+// TODO: Filtered Search APIs: https://github.com/rapidsai/cuvs/issues/363
+
 /**
  * @defgroup hnsw_cpp_index_search Search hnswlib index
  * @{
@@ -260,7 +262,7 @@ void search(raft::resources const& res,
 void search(raft::resources const& res,
             const search_params& params,
             const index<uint8_t>& idx,
-            raft::host_matrix_view<const int, int64_t, raft::row_major> queries,
+            raft::host_matrix_view<const uint8_t, int64_t, raft::row_major> queries,
             raft::host_matrix_view<uint64_t, int64_t, raft::row_major> neighbors,
             raft::host_matrix_view<float, int64_t, raft::row_major> distances);
 
@@ -303,7 +305,7 @@ void search(raft::resources const& res,
 void search(raft::resources const& res,
             const search_params& params,
             const index<int8_t>& idx,
-            raft::host_matrix_view<const int, int64_t, raft::row_major> queries,
+            raft::host_matrix_view<const int8_t, int64_t, raft::row_major> queries,
             raft::host_matrix_view<uint64_t, int64_t, raft::row_major> neighbors,
             raft::host_matrix_view<float, int64_t, raft::row_major> distances);
 

cpp/src/neighbors/cagra_c.cpp

@@ -176,6 +176,14 @@ extern "C" cuvsError_t cuvsCagraIndexDestroy(cuvsCagraIndex_t index_c_ptr)
   });
 }
 
+extern "C" cuvsError_t cuvsCagraIndexGetDims(cuvsCagraIndex_t index, int* dim)
+{
+  return cuvs::core::translate_exceptions([=] {
+    auto index_ptr = reinterpret_cast<cuvs::neighbors::cagra::index<float, uint32_t>*>(index->addr);
+    *dim           = index_ptr->dim();
+  });
+}
+
 extern "C" cuvsError_t cuvsCagraBuild(cuvsResources_t res,
                                       cuvsCagraIndexParams_t params,
                                       DLManagedTensor* dataset_tensor,

cpp/src/neighbors/detail/cagra/cagra_serialize.cuh

@@ -119,9 +119,9 @@ void serialize_to_hnswlib(raft::resources const& res,
   os.write(reinterpret_cast<char*>(&curr_element_count), sizeof(std::size_t));
   // Example:M: 16, dim = 128, data_t = float, index_t = uint32_t, list_size_type = uint32_t,
   // labeltype: size_t size_data_per_element_ = M * 2 * sizeof(index_t) + sizeof(list_size_type) +
-  // dim * 4 + sizeof(labeltype)
-  auto size_data_per_element =
-    static_cast<std::size_t>(index_.graph_degree() * sizeof(IdxT) + 4 + index_.dim() * 4 + 8);
+  // dim * sizeof(T) + sizeof(labeltype)
+  auto size_data_per_element = static_cast<std::size_t>(index_.graph_degree() * sizeof(IdxT) + 4 +
+                                                        index_.dim() * sizeof(T) + 8);
   os.write(reinterpret_cast<char*>(&size_data_per_element), sizeof(std::size_t));
   // label_offset
   std::size_t label_offset = size_data_per_element - 8;
@@ -184,18 +184,9 @@ void serialize_to_hnswlib(raft::resources const& res,
     }
 
     auto data_row = host_dataset.data_handle() + (index_.dim() * i);
-    if constexpr (std::is_same_v<T, float>) {
-      for (std::size_t j = 0; j < index_.dim(); ++j) {
-        auto data_elem = static_cast<float>(host_dataset(i, j));
-        os.write(reinterpret_cast<char*>(&data_elem), sizeof(float));
-      }
-    } else if constexpr (std::is_same_v<T, std::int8_t> or std::is_same_v<T, std::uint8_t>) {
-      for (std::size_t j = 0; j < index_.dim(); ++j) {
-        auto data_elem = static_cast<int>(host_dataset(i, j));
-        os.write(reinterpret_cast<char*>(&data_elem), sizeof(int));
-      }
-    } else {
-      RAFT_FAIL("Unsupported dataset type while saving CAGRA dataset to HNSWlib format");
+    for (std::size_t j = 0; j < index_.dim(); ++j) {
+      auto data_elem = static_cast<T>(host_dataset(i, j));
+      os.write(reinterpret_cast<char*>(&data_elem), sizeof(T));
     }
 
     os.write(reinterpret_cast<char*>(&i), sizeof(std::size_t));

cpp/src/neighbors/detail/hnsw.hpp

@@ -110,9 +110,9 @@ std::unique_ptr<index<T>> from_cagra(raft::resources const& res,
   return std::unique_ptr<index<T>>(hnsw_index);
 }
 
-template <typename QueriesT>
-void get_search_knn_results(hnswlib::HierarchicalNSW<QueriesT> const* idx,
-                            const QueriesT* query,
+template <typename T>
+void get_search_knn_results(hnswlib::HierarchicalNSW<typename hnsw_dist_t<T>::type> const* idx,
+                            const T* query,
                             int k,
                             uint64_t* indices,
                             float* distances)
@@ -127,11 +127,11 @@ void get_search_knn_results(hnswlib::HierarchicalNSW<QueriesT> const* idx,
   }
 }
 
-template <typename T, typename QueriesT>
+template <typename T>
 void search(raft::resources const& res,
             const search_params& params,
             const index<T>& idx,
-            raft::host_matrix_view<const QueriesT, int64_t, raft::row_major> queries,
+            raft::host_matrix_view<const T, int64_t, raft::row_major> queries,
             raft::host_matrix_view<uint64_t, int64_t, raft::row_major> neighbors,
             raft::host_matrix_view<float, int64_t, raft::row_major> distances)
 {
@@ -146,7 +146,8 @@ void search(raft::resources const& res,
 
   idx.set_ef(params.ef);
   auto const* hnswlib_index =
-    reinterpret_cast<hnswlib::HierarchicalNSW<QueriesT> const*>(idx.get_index());
+    reinterpret_cast<hnswlib::HierarchicalNSW<typename hnsw_dist_t<T>::type> const*>(
+      idx.get_index());
 
   // when num_threads == 0, automatically maximize parallelism
   if (params.num_threads) {

cpp/src/neighbors/hnsw.cpp

@@ -34,20 +34,20 @@ CUVS_INST_HNSW_FROM_CAGRA(int8_t);
 
 #undef CUVS_INST_HNSW_FROM_CAGRA
 
-#define CUVS_INST_HNSW_SEARCH(T, QueriesT)                                              \
-  void search(raft::resources const& res,                                               \
-              const search_params& params,                                              \
-              const index<T>& idx,                                                      \
-              raft::host_matrix_view<const QueriesT, int64_t, raft::row_major> queries, \
-              raft::host_matrix_view<uint64_t, int64_t, raft::row_major> neighbors,     \
-              raft::host_matrix_view<float, int64_t, raft::row_major> distances)        \
-  {                                                                                     \
-    detail::search<T, QueriesT>(res, params, idx, queries, neighbors, distances);       \
+#define CUVS_INST_HNSW_SEARCH(T)                                                    \
+  void search(raft::resources const& res,                                           \
+              const search_params& params,                                          \
+              const index<T>& idx,                                                  \
+              raft::host_matrix_view<const T, int64_t, raft::row_major> queries,    \
+              raft::host_matrix_view<uint64_t, int64_t, raft::row_major> neighbors, \
+              raft::host_matrix_view<float, int64_t, raft::row_major> distances)    \
+  {                                                                                 \
+    detail::search<T>(res, params, idx, queries, neighbors, distances);             \
   }
 
-CUVS_INST_HNSW_SEARCH(float, float);
-CUVS_INST_HNSW_SEARCH(uint8_t, int);
-CUVS_INST_HNSW_SEARCH(int8_t, int);
+CUVS_INST_HNSW_SEARCH(float);
+CUVS_INST_HNSW_SEARCH(uint8_t);
+CUVS_INST_HNSW_SEARCH(int8_t);
 
 #undef CUVS_INST_HNSW_SEARCH
 

cpp/src/neighbors/hnsw_c.cpp

@@ -31,7 +31,7 @@
 #include <cuvs/neighbors/hnsw.hpp>
 
 namespace {
-template <typename T, typename QueriesT>
+template <typename T>
 void _search(cuvsResources_t res,
              cuvsHnswSearchParams params,
              cuvsHnswIndex index,
@@ -46,7 +46,7 @@ void _search(cuvsResources_t res,
   search_params.ef          = params.ef;
   search_params.num_threads = params.numThreads;
 
-  using queries_mdspan_type   = raft::host_matrix_view<QueriesT const, int64_t, raft::row_major>;
+  using queries_mdspan_type   = raft::host_matrix_view<T const, int64_t, raft::row_major>;
   using neighbors_mdspan_type = raft::host_matrix_view<uint64_t, int64_t, raft::row_major>;
   using distances_mdspan_type = raft::host_matrix_view<float, int64_t, raft::row_major>;
   auto queries_mds            = cuvs::core::from_dlpack<queries_mdspan_type>(queries_tensor);
@@ -127,16 +127,13 @@ extern "C" cuvsError_t cuvsHnswSearch(cuvsResources_t res,
 
     auto index = *index_c_ptr;
     RAFT_EXPECTS(queries.dtype.code == index.dtype.code, "type mismatch between index and queries");
-    RAFT_EXPECTS(queries.dtype.bits == 32, "number of bits in queries dtype should be 32");
 
     if (index.dtype.code == kDLFloat) {
-      _search<float, float>(
-        res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
+      _search<float>(res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
     } else if (index.dtype.code == kDLUInt) {
-      _search<uint8_t, int>(
-        res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
+      _search<uint8_t>(res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
     } else if (index.dtype.code == kDLInt) {
-      _search<int8_t, int>(res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
+      _search<int8_t>(res, *params, index, queries_tensor, neighbors_tensor, distances_tensor);
     } else {
       RAFT_FAIL("Unsupported index dtype: %d and bits: %d", queries.dtype.code, queries.dtype.bits);
     }
@@ -152,13 +149,10 @@ extern "C" cuvsError_t cuvsHnswDeserialize(cuvsResources_t res,
   return cuvs::core::translate_exceptions([=] {
     if (index->dtype.code == kDLFloat && index->dtype.bits == 32) {
       index->addr = reinterpret_cast<uintptr_t>(_deserialize<float>(res, filename, dim, metric));
-      index->dtype.code = kDLFloat;
     } else if (index->dtype.code == kDLUInt && index->dtype.bits == 8) {
       index->addr = reinterpret_cast<uintptr_t>(_deserialize<uint8_t>(res, filename, dim, metric));
-      index->dtype.code = kDLInt;
     } else if (index->dtype.code == kDLInt && index->dtype.bits == 8) {
       index->addr = reinterpret_cast<uintptr_t>(_deserialize<int8_t>(res, filename, dim, metric));
-      index->dtype.code = kDLUInt;
     } else {
       RAFT_FAIL("Unsupported dtype in file %s", filename);
     }

docs/source/c_api/neighbors.rst

@@ -13,3 +13,4 @@ Nearest Neighbors
    neighbors_ivf_flat_c.rst
    neighbors_ivf_pq_c.rst
    neighbors_cagra_c.rst
+   neighbors_hnsw_c.rst

docs/source/cpp_api/neighbors.rst

@@ -11,6 +11,7 @@ Nearest Neighbors
 
    neighbors_bruteforce.rst
    neighbors_cagra.rst
+   neighbors_hnsw.rst
    neighbors_ivf_flat.rst
    neighbors_ivf_pq.rst
    neighbors_nn_descent.rst

docs/source/python_api/neighbors.rst

@@ -11,5 +11,6 @@ Nearest Neighbors
 
    neighbors_brute_force.rst
    neighbors_cagra.rst
+   neighbors_hnsw.rst
    neighbors_ivf_flat.rst
    neighbors_ivf_pq.rst

docs/source/python_api/neighbors_hnsw.rst

@@ -0,0 +1,30 @@
+HNSW
+====
+
+This is a wrapper for hnswlib, to load a CAGRA index as an immutable HNSW index. The loaded HNSW index is only compatible in cuVS, and can be searched using wrapper functions.
+
+.. role:: py(code)
+   :language: python
+   :class: highlight
+
+Index search parameters
+#######################
+
+.. autoclass:: cuvs.neighbors.hnsw.SearchParams
+    :members:
+
+Index
+#####
+
+.. autoclass:: cuvs.neighbors.hnsw.Index
+    :members:
+
+Index Conversion
+################
+
+.. autofunction:: cuvs.neighbors.hnsw.from_cagra
+
+Index search
+############
+
+.. autofunction:: cuvs.neighbors.hnsw.search

python/cuvs/cuvs/neighbors/CMakeLists.txt

@@ -14,6 +14,7 @@
 
 add_subdirectory(brute_force)
 add_subdirectory(cagra)
+add_subdirectory(hnsw)
 add_subdirectory(ivf_flat)
 add_subdirectory(ivf_pq)
 add_subdirectory(filters)

python/cuvs/cuvs/neighbors/cagra/cagra.pxd

@@ -17,6 +17,7 @@
 
 from libc.stdint cimport (
     int8_t,
+    int32_t,
     int64_t,
     uint8_t,
     uint32_t,
@@ -100,6 +101,8 @@ cdef extern from "cuvs/neighbors/cagra.h" nogil:
 
     cuvsError_t cuvsCagraIndexDestroy(cuvsCagraIndex_t index)
 
+    cuvsError_t cuvsCagraIndexGetDims(cuvsCagraIndex_t index, int32_t* dim)
+
     cuvsError_t cuvsCagraBuild(cuvsResources_t res,
                                cuvsCagraIndexParams* params,
                                DLManagedTensor* dataset,
@@ -117,6 +120,20 @@ cdef extern from "cuvs/neighbors/cagra.h" nogil:
                                    cuvsCagraIndex_t index,
                                    bool include_dataset) except +
 
+    cuvsError_t cuvsCagraSerializeToHnswlib(cuvsResources_t res,
+                                            const char * filename,
+                                            cuvsCagraIndex_t index) except +
+
     cuvsError_t cuvsCagraDeserialize(cuvsResources_t res,
                                      const char * filename,
                                      cuvsCagraIndex_t index) except +
+
+cdef class Index:
+    """
+    CAGRA index object. This object stores the trained CAGRA index state
+    which can be used to perform nearest neighbors searches.
+    """
+
+    cdef cuvsCagraIndex_t index
+    cdef bool trained
+    cdef str active_index_type

python/cuvs/cuvs/neighbors/cagra/cagra.pyx

@@ -36,6 +36,7 @@ from pylibraft.neighbors.common import _check_input_array
 
 from libc.stdint cimport (
     int8_t,
+    int32_t,
     int64_t,
     uint8_t,
     uint32_t,
@@ -206,16 +207,9 @@ cdef class IndexParams:
 
 
 cdef class Index:
-    """
-    CAGRA index object. This object stores the trained CAGRA index state
-    which can be used to perform nearest neighbors searches.
-    """
-
-    cdef cuvsCagraIndex_t index
-    cdef bool trained
-
     def __cinit__(self):
         self.trained = False
+        self.active_index_type = None
         check_cuvs(cuvsCagraIndexCreate(&self.index))
 
     def __dealloc__(self):
@@ -226,6 +220,12 @@ cdef class Index:
     def trained(self):
         return self.trained
 
+    @property
+    def dim(self):
+        cdef int32_t dim
+        check_cuvs(cuvsCagraIndexGetDims(self.index, &dim))
+        return dim
+
     def __repr__(self):
         # todo(dgd): update repr as we expose data through C API
         attr_str = []
@@ -299,6 +299,7 @@ def build(IndexParams index_params, dataset, resources=None):
             idx.index
         ))
         idx.trained = True
+        idx.active_index_type = dataset_ai.dtype.name
 
     return idx