Fed2Com: Towards Efficient Compression in Federated Learning

Federated learning (FL) is a distributed machine learning system that enables multiple clients to collaboratively train a machine learning model without sacrificing data privacy. In the last few years, various biased compression techniques have been proposed to alleviate the communication bottleneck in FL. However, these approaches rely on an ideal setting where all clients participate and continuously send their local errors to the cloud server. In this paper, we design a communication-efficient algorithmic framework called Fed2Com for FL with non-i.i.d datasets. In particular, Fed2Com has a two-level structure: At the client side, it leverages unbiased compression methods, e.g., rand-k sparsification, to compress the upload communication, avoiding leaving errors at the client. Then on the server side, Fed2Com applies biased compressors, e.g., top-k sparsification, with error correction to compress the download communication while stabilizing the training process. Fed2Com can achieve high compression ratio while maintaining robust performance against data heterogeneity. We conduct extensive experiments on MNIST, CIFAR10, Sentiment140 and PersonaChat datasets, and the evaluation results reveal the effectiveness of Fed2Com.