Attention
The vector search and clustering algorithms in RAFT are being migrated to a new library dedicated to vector search called cuVS. We will continue to support the vector search algorithms in RAFT during this move, but will no longer update them after the RAPIDS 24.06 (June) release. We plan to complete the migration by RAPIDS 24.08 (August) release.
KMeans#
#include <raft/cluster/kmeans_balanced.cuh>

template<typename DataT, typename MathT, typename IndexT, typename MappingOpT = raft::identity_op>
void raft::cluster::kmeans_balanced::fit(const raft::resources &handle, kmeans_balanced_params const ¶ms, raft::device_matrix_view<const DataT, IndexT> X, raft::device_matrix_view<MathT, IndexT> centroids, MappingOpT mapping_op = raft::identity_op())# Find clusters of balanced sizes with a hierarchical kmeans algorithm.
This variant of the kmeans algorithm first clusters the dataset in mesoclusters, then clusters the subsets associated to each mesocluster into fine clusters, and finally runs a few kmeans iterations over the whole dataset and with all the centroids to obtain the final clusters.
Each kmeans iteration applies expectationmaximizationbalancing:
Balancing: adjust centers for clusters that have a small number of entries. If the size of a cluster is below a threshold, the center is moved towards a bigger cluster.
Expectation: predict the labels (i.e find closest cluster centroid to each point)
Maximization: calculate optimal centroids (i.e find the center of gravity of each cluster)
The number of mesoclusters is chosen by rounding the square root of the number of clusters. E.g for 512 clusters, we would have 23 mesoclusters. The number of fine clusters per mesocluster is chosen proportionally to the number of points in each mesocluster.
This variant of kmeans uses random initialization and a fixed number of iterations, though iterations can be repeated if the balancing step moved the centroids.
Additionally, this algorithm supports quantized datasets in arbitrary types but the core part of the algorithm will work with a floatingpoint type, hence a conversion function can be provided to map the data type to the math type.
#include <raft/core/handle.hpp> #include <raft/cluster/kmeans_balanced.cuh> #include <raft/cluster/kmeans_balanced_types.hpp> ... raft::handle_t handle; raft::cluster::kmeans_balanced_params params; auto centroids = raft::make_device_matrix<float, int>(handle, n_clusters, n_features); raft::cluster::kmeans_balanced::fit(handle, params, X, centroids.view());
 Template Parameters:
DataT – Type of the input data.
MathT – Type of the centroids and mapped data.
IndexT – Type used for indexing.
MappingOpT – Type of the mapping function.
 Parameters:
handle – [in] The raft resources
params – [in] Structure containing the hyperparameters
X – [in] Training instances to cluster. The data must be in rowmajor format. [dim = n_samples x n_features]
centroids – [out] The generated centroids [dim = n_clusters x n_features]
mapping_op – [in] (optional) Functor to convert from the input datatype to the arithmetic datatype. If DataT == MathT, this must be the identity.

template<typename DataT, typename MathT, typename IndexT, typename LabelT, typename MappingOpT = raft::identity_op>
void raft::cluster::kmeans_balanced::predict(const raft::resources &handle, kmeans_balanced_params const ¶ms, raft::device_matrix_view<const DataT, IndexT> X, raft::device_matrix_view<const MathT, IndexT> centroids, raft::device_vector_view<LabelT, IndexT> labels, MappingOpT mapping_op = raft::identity_op())# Predict the closest cluster each sample in X belongs to.
#include <raft/core/handle.hpp> #include <raft/cluster/kmeans_balanced.cuh> #include <raft/cluster/kmeans_balanced_types.hpp> ... raft::handle_t handle; raft::cluster::kmeans_balanced_params params; auto labels = raft::make_device_vector<float, int>(handle, n_rows); raft::cluster::kmeans_balanced::predict(handle, params, X, centroids, labels);
 Template Parameters:
DataT – Type of the input data.
MathT – Type of the centroids and mapped data.
IndexT – Type used for indexing.
LabelT – Type of the output labels.
MappingOpT – Type of the mapping function.
 Parameters:
handle – [in] The raft resources
params – [in] Structure containing the hyperparameters
X – [in] Dataset for which to infer the closest clusters. [dim = n_samples x n_features]
centroids – [in] The input centroids [dim = n_clusters x n_features]
labels – [out] The output labels [dim = n_samples]
mapping_op – [in] (optional) Functor to convert from the input datatype to the arithmetic datatype. If DataT == MathT, this must be the identity.

template<typename DataT, typename MathT, typename IndexT, typename LabelT, typename MappingOpT = raft::identity_op>
void raft::cluster::kmeans_balanced::fit_predict(const raft::resources &handle, kmeans_balanced_params const ¶ms, raft::device_matrix_view<const DataT, IndexT> X, raft::device_matrix_view<MathT, IndexT> centroids, raft::device_vector_view<LabelT, IndexT> labels, MappingOpT mapping_op = raft::identity_op())# Compute hierarchical balanced kmeans clustering and predict cluster index for each sample in the input.
#include <raft/core/handle.hpp> #include <raft/cluster/kmeans_balanced.cuh> #include <raft/cluster/kmeans_balanced_types.hpp> ... raft::handle_t handle; raft::cluster::kmeans_balanced_params params; auto centroids = raft::make_device_matrix<float, int>(handle, n_clusters, n_features); auto labels = raft::make_device_vector<float, int>(handle, n_rows); raft::cluster::kmeans_balanced::fit_predict( handle, params, X, centroids.view(), labels.view());
 Template Parameters:
DataT – Type of the input data.
MathT – Type of the centroids and mapped data.
IndexT – Type used for indexing.
LabelT – Type of the output labels.
MappingOpT – Type of the mapping function.
 Parameters:
handle – [in] The raft resources
params – [in] Structure containing the hyperparameters
X – [in] Training instances to cluster. The data must be in rowmajor format. [dim = n_samples x n_features]
centroids – [out] The output centroids [dim = n_clusters x n_features]
labels – [out] The output labels [dim = n_samples]
mapping_op – [in] (optional) Functor to convert from the input datatype to the arithmetic datatype. If DataT and MathT are the same, this must be the identity.

struct kmeans_balanced_params : public raft::cluster::kmeans_base_params#
 #include <kmeans_balanced_types.hpp>
Simple object to specify hyperparameters to the balanced kmeans algorithm.
The following metrics are currently supported in kmeans balanced:
InnerProduct
L2Expanded
L2SqrtExpanded
Public Members

uint32_t n_iters = 20#
Number of training iterations