Dual Prototypes-Based Personalized Federated Adversarial Cross-Modal Hashing

With the rapid advances in wireless communication and IoT platforms, it is increasingly difficult to analyze relevant multi-modal data distributed across geographically diverse and heterogeneous platforms. One promising approach is to rely on federated learning to build compact cross-modal hash codes. However, existing federated learning methods easily exhibit degenerative performance in the global model due to the distributed data being derived from diverse domains. In addition, directly forcing each client to adopt the same global parameters as local parameters, without effective local training, significantly reduces the performance of each client. To overcome these challenges, we propose a novel federated adversarial cross-modal hashing, called Dual Prototypes-based personalized Federated Adversarial (DP-FeAd), which provides iterated training of shared dual prototypes. Specifically, aiming to expand local hashing models beyond their knowledge realms, DP-FeAd enables participating clients to engage in cooperative learning through two constructions: cluster prototypes and unbiased prototypes, instead of the traditional global prototypes, ensuring both generalization and stability. Specifically, the cluster prototypes are derived from local class-level prototypes and adversarially trained with local approximate hash codes to align their distributions. The unbiased prototypes are averaged from cluster prototypes and integrated into the training of local hashing models to maintain consistency across different local class-level prototypes further. The experiments conducted on two benchmark datasets demonstrate that our proposed method significantly enhances the performance of deep cross-modal hashing models in both IID (Independent and Identically Distributed) and non-IID scenarios.