Nearest Neighbor Classifier with Margin Penalty for Active Learning

TL;DR

This paper introduces NCMAL, a nearest neighbor classifier with a margin penalty and a new sample selection strategy, significantly improving active learning performance by better discovering informative samples with fewer annotations.

Contribution

The paper proposes a novel nearest neighbor classifier with margin penalty and a sample selection strategy to enhance active learning, addressing limitations of existing methods.

Findings

Achieves better results with fewer annotated samples

Ensures inter-class discrepancy and intra-class compactness

Outperforms state-of-the-art methods in experiments

Abstract

As deep learning becomes the mainstream in the field of natural language processing, the need for suitable active learning method are becoming unprecedented urgent. Active Learning (AL) methods based on nearest neighbor classifier are proposed and demonstrated superior results. However, existing nearest neighbor classifier are not suitable for classifying mutual exclusive classes because inter-class discrepancy cannot be assured by nearest neighbor classifiers. As a result, informative samples in the margin area can not be discovered and AL performance are damaged. To this end, we propose a novel Nearest neighbor Classifier with Margin penalty for Active Learning(NCMAL). Firstly, mandatory margin penalty are added between classes, therefore both inter-class discrepancy and intra-class compactness are both assured. Secondly, a novel sample selection strategy are proposed to discover informative samples within the margin area. To demonstrate the effectiveness of the methods, we conduct extensive experiments on for datasets with other state-of-the-art methods. The experimental results demonstrate that our method achieves better results with fewer annotated samples than all baseline methods.