Fig. 2

Illustration of various deep learning models. a Centralized Training: Depicts a model where users upload their individual training samples to a third-party entity, typically a cloud server with substantial computational resources, which is responsible for generating the final model. b Federated Learning Systems: Demonstrates an approach where models are trained locally, with only the gradients being shared, thereby ensuring that private data remains unexposed. c Decentralized Learning System: Represents a system where users have the autonomy to exchange gradients with their neighboring users and independently update their models