Peer-to-peer deep learning with non-IID data

Collaborative training of deep neural networks using edge devices has attracted substantial research interest recently. The two main architecture approaches for the training process are centrally orchestrated Federated Learning and fully decentralized peer-to-peer learning. In decentralized systems, edge devices, known as agents, collaborate in a peer-to-peer architecture, avoiding the need for a central system to orchestrate the process. Decentralized peer-to-peer (P2P) learning techniques are well researched under the assumption of independent and identically distributed (IID) data across the agents. IID data is seldom observed in real-world distributed systems, and the training performance varies significantly with non-IID data. This paper proposes a decentralized learning variant of the P2P gossip averaging method with Batch Normalization (BN) adaptation for P2P architectures. It is well-known that BN layers accelerate the convergence of the non-distributed deep learning models. Recent research confirms that Federated Learning methods benefit from using the BN method with some aggregation alterations. Our work demonstrated BN effectiveness in P2P architectures by mitigating the non-IID data characteristics across decentralized agents. We also introduce a variant of the early stopping technique that, combined with BN layers, acts as a fine-tuning technique for agent models. We validated our approach by conducting numerous simulations of different model-topology-communication combinations and comparing them to other decentralized baseline approaches. The evaluations were conducted on the next word prediction task using user comments from the Reddit and StackOverflow datasets representing comments from two different domains. Simulations showed that our approach, on average, achieves a mean relative top accuracy increase of 16.9% in ring (19.9% for Reddit, 13.9% for StackOverflow) and 29.8% in sparse (32.9% for Reddit, 26.6% for StackOverflow) communication topologies compared to the best baseline approach. Our code is available at https://github.com/fipu-lab/p2p_bn.