Research group · CDS
Distributed Learning Systems Group
Designing learning algorithms that work reliably when data, compute, and network resources are distributed across many nodes — without requiring centralized control.
Overview
The Distributed Learning Systems Group occupies a specific niche in machine learning research: we study what happens to learning algorithms when the data they need is spread across many autonomous agents, when communication is expensive or unreliable, and when the cost of computation must be shared. These conditions are the norm in industrial deployments, healthcare consortia, and IoT sensor networks — yet most published methods assume unrestricted access to centralized, homogeneous data.
Our work sits at the intersection of optimization theory, statistical learning theory, and systems research. We develop methods with provable convergence guarantees under realistic distributional assumptions: non-iid data across nodes, Byzantine-faulty participants, heterogeneous hardware, and intermittent connectivity. We pay close attention to the privacy properties of our algorithms, particularly in settings where raw gradients or activations could leak sensitive information about local datasets.
Beyond theory, we maintain active collaborations with the Meridian HPC facility for large-scale empirical validation, and with the Probabilistic Inference Lab on uncertainty-aware federated learning. Several group members contribute to open-source frameworks for federated learning used by external institutions. The group participates in the graduate program through the CDS doctoral track.
Research themes
- Federated optimization under data heterogeneity and partial participation
- Communication-efficient distributed training (compression, quantization, sparsification)
- Byzantine-robust aggregation and adversarial robustness in distributed settings
- Differential privacy in gradient-based learning
- Asynchronous and decentralized learning over peer-to-peer topologies
- Continual and lifelong learning across distributed agents
- Incentive design and fairness in multi-stakeholder learning systems
Current projects
Active · 2023–2026
FedHetero
Convergence analysis and adaptive aggregation rules for federated learning with extreme label and covariate shift across client datasets. Includes a benchmark suite of 12 realistic non-iid data partitions drawn from medical imaging and sensor network domains.
Funded by the Veyra Strategic Research Fund · 480,000 cr
Active · 2024–2027
PrivatePeer
A decentralized, fully peer-to-peer learning protocol with differential privacy guarantees. Eliminates the need for a trusted aggregation server while maintaining tight privacy budgets through a novel randomized gossiping mechanism.
Funded by the VIAS Core Grants Programme · 310,000 cr
Active · 2022–2025
RobustAgg
Byzantine-resilient aggregation methods for cross-device federated learning at scale. Develops geometric median variants and outlier-robust estimators that tolerate up to 30% malicious or misconfigured clients without accuracy degradation.
Collaborative grant with Probabilistic Inference Lab · 220,000 cr
Active · 2024–2026
GreenFed
Energy-aware scheduling and communication protocols for federated learning on heterogeneous edge devices. Develops workload-aware adaptive sparsification and asynchronous training pipelines that reduce per-round energy cost by up to 42% in simulation.
Funded by VIAS Sustainability Initiative · 160,000 cr
Selected publications
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Ravelo, N., Osei-Amponsah, B., & Takahashi, M. (2024). Adaptive aggregation weights for federated learning under severe label heterogeneity. Veyra Technical Reports. VEYRA-DOI:10.veyra/2024-dls-001
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Ravelo, N. & Ferris, D. (2023). PrivatePeer: Fully decentralized learning with local differential privacy. Proceedings of the VIAS Annual Machine Learning Symposium. VEYRA-DOI:10.veyra/2023-dls-004
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Osei-Amponsah, B., Patel, S., & Ravelo, N. (2023). Geometric robustness in Byzantine-tolerant federated aggregation. Veyra Preprint Series. VEYRA-DOI:10.veyra/2023-dls-007
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Takahashi, M. & Ravelo, N. (2022). Communication-sparsified federated training on intermittent networks. Veyra Technical Reports. VEYRA-DOI:10.veyra/2022-dls-002
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Ravelo, N., Eberhardt, T., & Kim, J. (2021). Uncertainty-aware model aggregation in federated learning. Joint publication with Probabilistic Inference Lab. VEYRA-DOI:10.veyra/2021-cds-011
People
The group is led by Dr. Naila Ravelo. Current members include postdoctoral researchers Borys Osei-Amponsah, Saanvi Patel, Mele Takahashi, and Diego Ferris; doctoral students Jiyeon Kim, Oran Nkemdirim, Lena Brandt, Thibault Desvaux, Arjun Mehrotra, Cassie Voronikova, Priti Sundaram, Hywel Gareth, and Anita Volkov; and four research engineers supporting infrastructure and benchmarking. The group welcomes applications through the VIAS Graduate School.