Federated Classification in Hyperbolic Spaces via Secure Aggregation of Convex Hulls
CoRR(2023)
摘要
Hierarchical and tree-like data sets arise in many applications, including
language processing, graph data mining, phylogeny and genomics. It is known
that tree-like data cannot be embedded into Euclidean spaces of finite
dimension with small distortion. This problem can be mitigated through the use
of hyperbolic spaces. When such data also has to be processed in a distributed
and privatized setting, it becomes necessary to work with new federated
learning methods tailored to hyperbolic spaces. As an initial step towards the
development of the field of federated learning in hyperbolic spaces, we propose
the first known approach to federated classification in hyperbolic spaces. Our
contributions are as follows. First, we develop distributed versions of convex
SVM classifiers for Poincaré discs. In this setting, the information conveyed
from clients to the global classifier are convex hulls of clusters present in
individual client data. Second, to avoid label switching issues, we introduce a
number-theoretic approach for label recovery based on the so-called integer
B_h sequences. Third, we compute the complexity of the convex hulls in
hyperbolic spaces to assess the extent of data leakage; at the same time, in
order to limit communication cost for the hulls, we propose a new quantization
method for the Poincaré disc coupled with Reed-Solomon-like encoding. Fourth,
at the server level, we introduce a new approach for aggregating convex hulls
of the clients based on balanced graph partitioning. We test our method on a
collection of diverse data sets, including hierarchical single-cell RNA-seq
data from different patients distributed across different repositories that
have stringent privacy constraints. The classification accuracy of our method
is up to ∼ 11% better than its Euclidean counterpart, demonstrating the
importance of privacy-preserving learning in hyperbolic spaces.
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关键词
hyperbolic spaces,classification,secure aggregation
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