Papers › FreeAnchor: Learning to Match Anchors for Visual Object Detection
FreeAnchor: Learning to Match Anchors for Visual Object Detection
Xiaosong Zhang, Fang Wan, Chang Liu, Rongrong Ji, Qixiang Ye
Modern CNN-based object detectors assign anchors for ground-truth objects under the restriction of object-anchor Intersection-over-Unit (IoU). In this study, we propose a learning-to-match approach to break IoU restriction, allowing objects to match anchors in a flexible manner. Our approach, referred to as FreeAnchor, updates hand-crafted anchor assignment to "free" anchor matching by formulating detector training as a maximum likelihood estimation (MLE) procedure. FreeAnchor targets at learning features which best explain a class of objects in terms of both classification and localization. FreeAnchor is implemented by optimizing detection customized likelihood and can be fused with CNN-based detectors in a plug-and-play manner. Experiments on COCO demonstrate that FreeAnchor consistently outperforms their counterparts with significant margins.
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Code
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Tasks
Results from the paper archive 2025-07-28
| Task | Dataset | Model | Metric | Value | Rank at snapshot | Leaderboard | Report |
|---|---|---|---|---|---|---|---|
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | AP50 | 64.3 | #140 of 225 | Archive leaderboard | report |
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | AP75 | 48.4 | #140 of 225 | Archive leaderboard | report |
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | APL | 56 | #140 of 225 | Archive leaderboard | report |
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | APM | 47.9 | #140 of 225 | Archive leaderboard | report |
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | APS | 27 | #140 of 225 | Archive leaderboard | report |
| Object Detection | COCO test-dev | FreeAnchor (ResNeXt-101) | box mAP | 44.8 | #140 of 225 | Archive leaderboard | report |
Ranks are positions in the archive's leaderboards as they stood at the 2025-07-28 snapshot. Results published since then are not among these rows, so a rank here is not a current standing.
Methods
Introduced by this paper: FreeAnchor
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