  Deep active learning in the presence of outlier examples poses a realistic
yet challenging scenario. Acquiring unlabeled data for annotation requires a
delicate balance between avoiding outliers to conserve the annotation budget
and prioritizing useful inlier examples for effective training. In this work,
we present an approach that leverages three highly synergistic components,
which are identified as key ingredients: joint classifier training with inliers
and outliers, semi-supervised learning through pseudo-labeling, and model
ensembling. Our work demonstrates that ensembling significantly enhances the
accuracy of pseudo-labeling and improves the quality of data acquisition. By
enabling semi-supervision through the joint training process, where outliers
are properly handled, we observe a substantial boost in classifier accuracy
through the use of all available unlabeled examples. Notably, we reveal that
the integration of joint training renders explicit outlier detection
unnecessary; a conventional component for acquisition in prior work. The three
key components align seamlessly with numerous existing approaches. Through
empirical evaluations, we showcase that their combined use leads to a
performance increase. Remarkably, despite its simplicity, our proposed approach
outperforms all other methods in terms of performance. Code:
https://github.com/vladan-stojnic/active-outliers

Computer Vision and Pattern Recognition