arXiv Machine Learning

On Johnson-Lindenstrauss Transforms for Byzantine-Robust Optimization

The paper investigates the use of Johnson‑Lindenstrauss (JL) transforms in Byzantine‑robust distributed optimization. By leveraging JL’s ability to preserve inner products and distances, worker messages are weighted based on their alignment with a trusted reference gradient, reducing communication costs while maintaining robustness. Experimental results support the theoretical claims.

arXiv Machine Learning
Oct 3

FedFit: Federated Fine-Tuning of LLMs via Vector-Bank Parameterization and Quantization

FedFit introduces a federated fine‑tuning framework for large language models that reduces communication overhead by using a disjoint shared vector‑bank parameterization to reconstruct adapter matrices from two compact global vector banks. It resolves the aggregation dilemma between Sum‑of‑Products and Product‑of‑Sums through an alternating optimization schedule that alternates between accurate single‑bank updates and joint updates corrected by a Residual Spectral Aggregation mechanism. The method also incorporates blockwise quantization with client‑side error feedback and provides theoretical convergence guarantees, achieving perplexity comparable to standard federated LoRA while delivering up to 100× higher compression ratios on Qwen2.5 models.

By Hang Zou, Chao Zhang, Yuzhi Yang, Yu Tian, Samson Lasaulce, M\'erouane Debbah
arXiv Machine Learning
Sep 4

A Nesterov-Accelerated Byzantine-Robust Federated Learning

The paper proposes Byrd-NAFL, a Byzantine‑robust federated learning algorithm that incorporates Nesterov’s momentum and resilient aggregation rules. It achieves fast and safe convergence under non‑convex, smooth loss functions with relaxed gradient assumptions, and provides a finite‑time convergence guarantee. Experiments show that Byrd-NAFL outperforms existing methods in convergence speed, accuracy, and resilience to various malicious attacks.

By Lihan Xu, Xiaoyi Fan, Gang Wang, Runhao Zeng, Xiping Hu, Yanjie Dong
arXiv Machine Learning
Oct 12

Approximating Uniform Random Rotations by Two-Stage Structured Hadamard Rotations in High Dimensions

The paper investigates how well two-stage structured Hadamard rotations approximate uniform random rotations in high-dimensional spaces. It establishes nonasymptotic upper bounds of order √{log d/d} for one-dimensional marginals, while showing a persistent Wasserstein-1 discrepancy for the full vector that does not vanish as dimension grows. These results highlight a separation between marginal and joint approximation quality, though they do not directly translate into algorithmic performance guarantees.

By Tomer Zilca, Gal Mendelson