Traditional Federated Learning (FL) focuses on collaborative global model training while ensuring privacy and personalization. Decentralized Federated Learning (DFL), a variant of FL, allows clients to independently manage and optimize local models without a central server. DFL reduces centralized communication bottlenecks and vulnerability to server failures or attacks. However, because the optimization dynamics change and there is no global model, generalization can suffer, making effective learning under data and model heterogeneity a critical challenge in DFL. Despite growing interest in DFL, the lack of distributional and uncertainty modeling in the literature limits reliability and effective generalization in non-IID settings. In this work, we propose DFedDG2, a personalized federated learning framework that operates within a peer-to-peer protocol. DFedDG2 offers the technical advantage of modeling each client’s local data distribution and exchanging this information with one-hop neighbors. In the decentralized network, clients perform distribution-aware gossip, where statistically similar clients exert greater influence to drive global alignment. This likelihood-weighted mixing fuses only a handful of vectors and scalars, significantly reducing communication costs while aligning semantic spaces across the network and enabling personalized training at the edge. In addition, theoretically, we prove that DFedDG2 achieves a sublinear convergence rate while the consensus error decays at a geometric rate under well-principled properties of gossip. Unlike the label-only non-IID experiments in DFL literature, we conduct extensive experiments on multiple data non-IID scenarios, topology variations, model heterogeneity, and uncertainty quantification, demonstrating the practical advantages of DFedDG2. Our results show that DFedDG2 not only achieves communication efficiency but also provides better generalization and improved reliability compared to state-of-the-art approaches.

We consider the problem of inferring node labels in a partially labeled graph where each node in the graph has multiple label types and each label type has a large number of possible labels. Our primary example, and the focus of this paper, is the joint inference of label types such as hometown, current city, and employers for people connected by a social network; by predicting these user profile fields, the network can provide a better experience to its users. Existing approaches such as Label Propagation (Zhu et al., 2003) fail to consider interactions between the label types. Our proposed method, called EDGEEXPLAIN explicitly models these interactions, while still allowing scalable inference under a distributed message- passing architecture. On a large subset of the Facebook social network, collected in a previous study (Chakrabarti et al., 2014), EDGEEXPLAIN outperforms label propagation for several label types, with lifts of up to $120\%$ for recall@1 and $60\%$ for recall@3.

We tackle the problem of inferring node labels in a partially labeled graph where each node in the graph has multiple label types and each label type has a large number of possible labels. Our primary example, and the focus of this paper, is the joint inference of label types such as hometown, current city, and employers, for users connected by a social network. Standard label propagation fails to consider the properties of the label types and the interactions between them. Our proposed method, called EdgeExplain, explicitly models these, while still enabling scalable inference under a distributed message-passing architecture. On a billion-node subset of the Facebook social network, EdgeExplain significantly outperforms label propagation for several label types, with lifts of up to 120% for recall@1 and 60% for recall@3.

Camera networks are perhaps the most common type of sensor network and are deployed in a variety of real-world applications including surveillance, intelligent environments and scientific remote monitoring. A key problem in deploying a network of cameras is calibration, i.e., determining the location and orientation of each sensor so that observations in an image can be mapped to locations in the real world. This paper proposes a fully distributed approach for camera network calibration. The cameras collaborate to track an object that moves through the environment and reason probabilistically about which camera poses are consistent with the observed images. This reasoning employs sophisticated techniques for handling the difficult nonlinearities imposed by projective transformations, as well as the dense correlations that arise between distant cameras. Our method requires minimal overlap of the cameras' fields of view and makes very few assumptions about the motion of the object. In contrast to existing approaches, which are centralized, our distributed algorithm scales easily to very large camera networks. We evaluate the system on a real camera network with 25 nodes as well as simulated camera networks of up to 50 cameras and demonstrate that our approach performs well even when communication is lossy.

We present a robust distributed algorithm for approximate probabilistic inference in dynamical systems, such as sensor networks and teams of mobile robots. Using assumed density filtering, the network nodes maintain a tractable representation of the belief state in a distributed fashion. At each time step, the nodes coordinate to condition this distribution on the observations made throughout the network, and to advance this estimate to the next time step. In addition, we identify a significant challenge for probabilistic inference in dynamical systems: message losses or network partitions can cause nodes to have inconsistent beliefs about the current state of the system. We address this problem by developing distributed algorithms that guarantee that nodes will reach an informative consistent distribution when communication is re-established. We present a suite of experimental results on real-world sensor data for two real sensor network deployments: one with 25 cameras and another with 54 temperature sensors.

We propose a demonstration of extremely scalable modular robotics algorithms developed as part of the Claytronics Project (http://www-2.cs.cmu.edu/~claytronics/), as well as a demonstration of proof-of-concept prototypes. Our effort envisions multi-million-module robot ensembles able to morph into three-dimensional scenes, eventually with sufficient fidelity so as to convince a human observer the scenes are real. Although this work is potentially revolutionary in the sense that it holds out the possibility of radically altering the relationship between computation, humans, and the physical world, many of the research questions involved are similar in flavor to more mainstream systems research, albeit larger in scale. For instance, as in sensor networks, each robot will incorporate sensing, computation, and communications components. However, unlike most sensor networks each robot will also include mechanisms for actuation and motion. Many of the key challenges in this project involve coordination and communication of sensing and actuation across such large ensembles of independent units.