OTA
Deciding which gt to assign to which anchor is an important problem in object detection, namely the label assignment problem. OTA offers a new angle on this problem: treating label assignment as an optimal transport problem. Label Assignment Previous label assignment strategies are mainly divided into two kinds: fixed and dynamic. For fixed label assignment, Anchor-based detection models usually use an IoU threshold as the assignment criterion (such as Fast-RCNN, Faster-RCNN, YoLo3, RetinaNet and so on), while some Anchor-free detection models designate anchors within a certain range of the object center as positive samples (such as FCOS, Foveabox and so on). Fixed assignment methods usually adopt a fixed assignment strategy (for example a fixed IoU threshold or a fixed radius), which is the same for objects of different sizes and shapes, so the model may end up with a suboptimal assignment. ...