arXiv Machine Learning

From Classifier Heads to Encoder Prototypes: Personalized Federated Learning with Head-Derived Clustering

The paper introduces HDC‑FL, a personalized federated learning method that clusters clients based on their classifier heads, constructs encoder prototypes for each cluster, and returns a soft mixture of these prototypes to clients while keeping their heads private. The approach requires no additional optimization steps or fine‑tuning and preserves the shared‑encoder trajectory. Experiments on CIFAR‑10 and CIFAR‑100 with ResNet‑18 and MobileNetV2 show that HDC‑FL matches or surpasses state‑of‑the‑art personalized and clustered baselines in macro‑averaged accuracy, worst‑client performance, and bottom‑20% accuracy across various heterogeneity settings.

arXiv AI
Sep 24

A Shared Encoder Is Not a Shared Task: Conditional Comparison for Deep Expert Pools

The paper demonstrates that sharing a deep encoder alone does not eliminate the confounding effects in task-comparison scores. By introducing a conditional two‑discriminator discrepancy within the embedding space, the authors achieve robust detection of task changes, maintaining stability under input rotations and accurately tracking label‑permutation drift. This approach, integrated into a mixture‑of‑heads framework, outperforms traditional novelty triggers and generalizes across multiple backbones and datasets, including ImageNet‑21k ViT‑B/16, DINOv2, and CIFAR‑100.

By Kentaro Oda
arXiv Machine Learning
Oct 8

ORDERS: An Empirical Study of Norm-Rank Aggregation for Personalized Federated Learning

ORDERS is a personalized federated learning configuration that combines a shared backbone, private residual adapters, and a classifier, using geometric weights based on descending update norms, feature alignment, and private‑parameter perturbations. In extensive experiments on CIFAR‑10 and Sent140, ORDERS achieves slightly higher mean client accuracy than baseline methods, with a 5.47% reduction in parameter payload. Ablation studies show limited, dataset‑dependent benefits from norm ranking and alignment, and no clear advantage from perturbations.

By Koffka Khan
arXiv Machine Learning
5d ago

Beyond Scarcity: When Encoder Adaptation Is Worthwhile

The paper introduces a controlled evaluation framework to determine when encoder adaptation is beneficial after correcting for class imbalance in long‑tailed recognition tasks. By separating unique support from representation allocation and comparing classifier‑only versus full‑network continuations, the study shows that encoder updates become worthwhile only when representation allocation is highly imbalanced, a transition that persists across various corrections and scales to ImageNet. The framework uses stage‑specific controls, multiple objectives, whole‑distribution metrics, and hierarchical inference to robustly estimate incremental encoder value.

By Zexing Zhang, Jichao Li, Tianyang Lei, Yiyin Zhang, Kewei Yang
arXiv AI
Sep 24

What Changed? Drift Detection with Real, Virtual, and Incomparable Diagnosis

The paper investigates drift detection in deep learning models, showing that sharing a deep encoder alone does not eliminate confounding in task-comparison scores. By introducing a conditional two‑discriminator discrepancy into the embedding space, the authors create a two‑axis gate that remains stable under input rotations and accurately tracks label‑permutation drift. This approach outperforms traditional exchange or novelty triggers, achieving high AUROC in distinguishing semantic novelty from photometric shift across multiple backbones and datasets.

By Kentaro Oda
arXiv Machine Learning
Sep 22

Joint Domain-Class Modeling for Federated Learning Under Feature Skew

The paper introduces Joint Domain-Class Federated Learning (JDFL), a lightweight, optimizer‑agnostic extension designed to address feature skew in federated learning. JDFL infers pseudo‑domains from local update signals and expands the classifier head to output joint domain‑class logits, enabling the model to capture domain‑conditioned appearance while sharing a backbone. Two supervision strategies—similarity‑aware soft‑labeling and per‑sample randomized target assignment—are proposed to train the expanded head, and experiments on domain‑shifted image benchmarks show consistent improvements in global test accuracy over standard FL methods.

By Sina Najafi, Mostafa Tavassolipour, Seyed Pooya Shariatpanahi
arXiv Machine Learning
Sep 22

Tackling Feature-Classifier Mismatch in Federated Learning via Prompt-Driven Feature Transformation

The paper introduces FedPFT, a federated learning framework that tackles the feature‑classifier mismatch problem by using personalized prompts processed through a shared self‑attention transformation module. Unlike prior methods that either degrade the feature extractor or address the mismatch only after training, FedPFT aligns local features with the global classifier during training, improving aggregation and model performance. Experiments demonstrate that FedPFT surpasses state‑of‑the‑art methods by up to 5.07%, and gains up to 7.08% when combined with collaborative contrastive learning.

By Xinghao Wu, Xuefeng Liu, Jianwei Niu, Guogang Zhu, Mingjia Shi, Shaojie Tang, Jing Yuan
arXiv Machine Learning
Aug 31

Ampere: Communication-Efficient and High-Accuracy Split Federated Learning

Ampere is a new split federated learning system that reduces both on‑device computation and device‑server communication while improving accuracy. It trains device and server blocks sequentially with local losses, eliminating gradient transfers, and uses a lightweight auxiliary network to consolidate activations into a single transfer. Experiments on CNNs and Transformers show up to 11.70 pp accuracy gains, 18.6× faster training, 911× less communication, and 14.5× less computation compared to state‑of‑the‑art SFL baselines.

By Zihan Zhang, Leon Wong, Blesson Varghese
arXiv Machine Learning
Oct 3

FedSAP: Federated Learning with Structured Adaptive Partitioning for Multi-Domain Heterogeneous Edge Devices

FedSAP is a federated learning framework that addresses heterogeneous edge devices by using structured pruning as a budget-constrained tri-state channel allocation. It partitions model channels into a Global pool, pseudo-domain-specific Private pools, and a Dropped state, allowing broadly useful features to be shared while isolating domain-sensitive updates. Experiments on Digits and Office-Caltech datasets show FedSAP achieving higher mean global accuracy than the strongest baseline while supporting up to 80% client pruning ratios.

By Wentao Yue, Tianyou Lai, Hongji Li, Qingyu Mao, Qilei Li