Pseudo-IoU: Improving Label Assignment in Anchor-Free Object Detection

Jiachen Li, Bowen Cheng, Rogerio Feris, Jinjun Xiong, Thomas S. Huang, Wen-Mei Hwu, Humphrey Shi; Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR) Workshops, 2021, pp. 2378-2387


Current anchor-free object detectors are quite simple and effective yet lack accurate sample assignment methods, which limits their potential in competing with classic anchor-based models that are supported by well-designed assignment methods based on the Intersection-over-Union (IoU) metric. In this paper, we present Pseudo-Intersection-over-Union (Pseudo-IoU): a simple metric that brings more standardized and accurate assignment rule into anchor-free object detection frameworks without any additional computational cost or extra parameters for training and testing, making it possible to further improve anchor-free object detection by utilizing training samples of good quality under effective assignment rules that have been previously applied in anchor-based methods. By incorporating Pseudo-IoU metric into an end-to-end single-stage anchor-free object detection framework, we observe consistent improvements in their performance on general object detection benchmarks such as PASCAL VOC and MSCOCO. Our method (single-model and single-scale) also achieves comparable performance to other recent state-of-the-art anchor-free methods without bells and whistles. Our code is based on mmdetection toolbox and will be made publicly available at

Related Material

@InProceedings{Li_2021_CVPR, author = {Li, Jiachen and Cheng, Bowen and Feris, Rogerio and Xiong, Jinjun and Huang, Thomas S. and Hwu, Wen-Mei and Shi, Humphrey}, title = {Pseudo-IoU: Improving Label Assignment in Anchor-Free Object Detection}, booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR) Workshops}, month = {June}, year = {2021}, pages = {2378-2387} }