arXiv Computer Vision

Active Learning under Simulated Class Imbalance and Label Shift in Binary Semantic Segmentation

The paper investigates how class imbalance and label shift—common in machine vision due to abundant defect‑free images and limited storage—affect active learning for binary semantic segmentation. It introduces a reproducible simulation protocol that independently varies these two imbalance factors using two open‑source datasets. Four active‑learning strategies (random, entropy‑based, core‑set, and galaxy sampling) are compared, showing that entropy‑based and core‑set methods generally outperform random sampling even under severe imbalance, while quantifying efficiency loss under strong label shift.

arXiv Computer Vision
Sep 18

Distance to Class Prototypes: Active Learning for Object Detection

The paper introduces a new active learning signal for object detection that relies on a supervised contrastive term added to the training objective. This term shapes an embedding space where distance reflects class membership, allowing an unlabeled detection to be scored by its distance from the predicted category’s region weighted by confidence—all from a single forward pass of one network. Experiments on PASCAL VOC and MS‑COCO show that this criterion outperforms the standard posterior and remains competitive with ensemble‑based methods while incurring only a modest 8.3% increase in parameters.

By Licheng Zhang, Zheng Gong
arXiv Machine Learning
Oct 22

Estimating Performance for Safe Deployment of Machine Learning Models

The paper introduces MOVAL, a model evaluation tool that estimates performance of deep neural networks on unlabeled test data by calibrating class-wise confidence scores. MOVAL mitigates issues from distributional shifts and class imbalance, enabling estimation of metrics beyond accuracy such as F1-Score and AUC. Experiments on natural and medical image datasets demonstrate state‑of‑the‑art results across classification and segmentation tasks, providing accurate class, instance, and pixel‑level performance estimates for safe deployment.

By Zeju Li, Konstantinos Kamnitsas, Mobarakol Islam, Melanie Roschewitz, Cheng Ouyang, Chen Chen, Ben Glocker
arXiv AI
Oct 27

PCoreSet: Effective Active Learning through Knowledge Distillation from Vision-Language Models

The paper introduces ActiveKD, a framework that combines active learning with knowledge distillation by using large vision‑language models as teachers. It leverages the structured prediction bias of these models to design Probabilistic CoreSet (PCoreSet), a selection strategy that maximizes coverage in probability space rather than feature space. Experiments on 11 datasets show that ActiveKD improves all selection methods over a no‑distillation baseline, and PCoreSet consistently outperforms random sampling across multiple students and teachers.

By Seongjae Kang, Dong Bok Lee, Hyungjoon Jang, Dongseop Kim, Sung Ju Hwang