One-shot federated learning (OSFL) has gained attention in recent years due
to its low communication cost. However, most of the existing methods require
auxiliary datasets or training generators, which hinders their practicality in
real-world scenarios. In this paper, we explore the novel opportunities that
diffusion models bring to OSFL and propose FedCADO, utilizing guidance from
client classifiers to generate data that complies with clients' distributions
and subsequently training the aggregated model on the server. Specifically, our
method involves targeted optimizations in two aspects. On one hand, we
conditionally edit the randomly sampled initial noises, embedding them with
specified semantics and distributions, resulting in a significant improvement
in both the quality and stability of generation. On the other hand, we employ
the BN statistics from the classifiers to provide detailed guidance during
generation. These tailored optimizations enable us to limitlessly generate
datasets, which closely resemble the distribution and quality of the original
client dataset. Our method effectively handles the heterogeneous client models
and the problems of non-IID features or labels. In terms of privacy protection,
our method avoids training any generator or transferring any auxiliary
information on clients, eliminating any additional privacy leakage risks.
Leveraging the extensive knowledge stored in the pre-trained diffusion model,
the synthetic datasets can assist us in surpassing the knowledge limitations of
the client samples, resulting in aggregation models that even outperform the
performance ceiling of centralized training in some cases, which is
convincingly demonstrated in the sufficient quantification and visualization
experiments conducted on three large-scale multi-domain image datasets.

使用扩散模型，在一次联邦学习中引入了指导性生成数据，避免了现实场景中常见的辅助数据集或训练生成器的障碍。该方法针对异构客户模型和非独立同分布的特征或标签问题，有效处理隐私保护并在一些情况下超越集中式训练的性能上限，从而形成性能更高的聚合模型。