Personalized federated learning is aimed at allowing numerous clients to
train personalized models while participating in collaborative training in a
communication-efficient manner without exchanging private data. However, many
personalized federated learning algorithms assume that clients have the same
neural network architecture, and those for heterogeneous models remain
understudied. In this study, we propose a novel personalized federated learning
method called federated classifier averaging (FedClassAvg). Deep neural
networks for supervised learning tasks consist of feature extractor and
classifier layers. FedClassAvg aggregates classifier weights as an agreement on
decision boundaries on feature spaces so that clients with not independently
and identically distributed (non-iid) data can learn about scarce labels. In
addition, local feature representation learning is applied to stabilize the
decision boundaries and improve the local feature extraction capabilities for
clients. While the existing methods require the collection of auxiliary data or
model weights to generate a counterpart, FedClassAvg only requires clients to
communicate with a couple of fully connected layers, which is highly
communication-efficient. Moreover, FedClassAvg does not require extra
optimization problems such as knowledge transfer, which requires intensive
computation overhead. We evaluated FedClassAvg through extensive experiments
and demonstrated it outperforms the current state-of-the-art algorithms on
heterogeneous personalized federated learning tasks.Comment: Accepted to ICPP 2022. Code: https://github.com/hukla/fedclassav