{"url":"/method/fsaf","slug":"fsaf","name":"FSAF","full_name":"FSAF","full_name_withheld":false,"description_markdown":"**FSAF**, or Feature Selective Anchor-Free, is a building block for single-shot object detectors. It can be plugged into single-shot detectors with feature pyramid structure. The FSAF module addresses two limitations brought up by the conventional anchor-based detection: 1) heuristic-guided feature selection; 2) overlap-based anchor sampling. The general concept of the FSAF module is online feature selection applied to the training of multi-level anchor-free branches. Specifically, an anchor-free branch is attached to each level of the feature pyramid, allowing box encoding and decoding in the anchor-free manner at an arbitrary level. During training, we dynamically assign each instance to the most suitable feature level. At the time of inference, the FSAF module can work jointly with anchor-based branches by outputting predictions in parallel. We instantiate this concept with simple implementations of anchor-free branches and online feature selection strategy\r\n\r\nThe general concept is presented in the Figure to the right. An anchor-free branch is built per level of feature pyramid, independent to the anchor-based branch. Similar to the anchor-based branch, it consists of a classification subnet and a regression subnet (not shown in figure). An instance can be assigned to arbitrary level of the anchor-free branch. During training, we dynamically select the most suitable level of feature for each instance based on the instance content instead of just the size of instance box. The selected level of feature then learns to detect the assigned instances. At inference, the FSAF module can run independently or jointly with anchor-based branches. The FSAF module is agnostic to the backbone network and can be applied to single-shot detectors with a structure of feature pyramid. Additionally, the instantiation of anchor-free branches and online feature selection can be various.","description_state":"present","introduced_year":null,"introduced_by":{"title":"Feature Selective Anchor-Free Module for Single-Shot Object Detection","paper":"/paper/feature-selective-anchor-free-module-for","first_author":"Chenchen Zhu","n_authors":3,"url_abs":null,"archive_paper_url":"https://paperswithcode.com/paper/feature-selective-anchor-free-module-for"},"source":{"url":"http://arxiv.org/abs/1903.00621v1","title":"Feature Selective Anchor-Free Module for Single-Shot Object Detection","url_on_a_paper_host":true},"code_snippet_url":"https://github.com/hdjang/Feature-Selective-Anchor-Free-Module-for-Single-Shot-Object-Detection/blob/d6ba356e0e9b65d658752fa7b712368addec7e31/mmdet/models/detectors/fsaf.py#L8","code_snippet_url_on_a_code_host":true,"categories":[{"area":"Computer Vision","area_id":"computer-vision","collection":"Feature Extractors","url":"/methods/category/feature-extractors","pwc_aliases":[]}],"n_papers_tagged":7,"archive_num_papers":7,"papers_newest_first":[{"paper":null,"title":"FAD-SAR: A Novel Fishing Activity Detection System via Synthetic Aperture Radar Images Based on Deep Learning Method","date":"2024-04-28","arxiv_id":"2404.18245","n_code_links":0,"syntology":null},{"paper":"/paper/deep-learning-approaches-to-building-rooftop","title":"Deep learning approaches to building rooftop thermal bridge detection from aerial images","date":"2022-12-12","arxiv_id":null,"n_code_links":1,"syntology":null},{"paper":null,"title":"Lost in Compression: the Impact of Lossy Image Compression on Variable Size Object Detection within Infrared Imagery","date":"2022-05-16","arxiv_id":"2205.08002","n_code_links":0,"syntology":null},{"paper":null,"title":"Fracture Detection in Wrist X-ray Images Using Deep Learning-Based Object Detection Models","date":"2021-11-14","arxiv_id":"2111.07355","n_code_links":0,"syntology":null},{"paper":null,"title":"Reinforced Few-Shot Acquisition Function Learning for Bayesian Optimization","date":"2021-06-08","arxiv_id":"2106.04335","n_code_links":0,"syntology":null},{"paper":null,"title":"AGSFCOS: Based on attention mechanism and Scale-Equalizing pyramid network of object detection","date":"2021-05-20","arxiv_id":"2105.09596","n_code_links":0,"syntology":null},{"paper":"/paper/feature-selective-anchor-free-module-for","title":"Feature Selective Anchor-Free Module for Single-Shot Object Detection","date":"2019-03-02","arxiv_id":"1903.00621","n_code_links":4,"syntology":{"ran":0,"of":8,"unverified":8,"pointer_only":0}}],"papers_shown":7,"tasks":[{"task":"/task/object-detection","name":"Object Detection","papers":6},{"task":"/task/object-detection-1","name":"object-detection","papers":5},{"task":"/task/action-detection","name":"Action Detection","papers":1},{"task":"/task/activity-detection","name":"Activity Detection","papers":1},{"task":null,"name":"Avg","papers":1},{"task":"/task/bayesian-optimization","name":"Bayesian Optimization","papers":1},{"task":"/task/ensemble-learning","name":"Ensemble Learning","papers":1},{"task":"/task/fad","name":"FAD","papers":1},{"task":"/task/few-shot-learning","name":"Few-Shot Learning","papers":1},{"task":"/task/fracture-detection","name":"Fracture detection","papers":1},{"task":"/task/image-compression","name":"Image Compression","papers":1},{"task":"/task/instance-segmentation","name":"Instance Segmentation","papers":1},{"task":"/task/medical-object-detection","name":"Medical Object Detection","papers":1},{"task":"/task/meta-learning","name":"Meta-Learning","papers":1},{"task":"/task/object","name":"Object","papers":1},{"task":"/task/transfer-learning","name":"Transfer Learning","papers":1},{"task":"/task/vessel-detection","name":"Vessel Detection","papers":1},{"task":"/task/feature-selection","name":"feature selection","papers":1}],"tasks_shown":18,"n_tasks":18,"usage_by_year":[{"year":"2019","papers":1},{"year":"2021","papers":3},{"year":"2022","papers":2},{"year":"2024","papers":1}],"row_source":"methods_table","archive":{"source":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","archive_url":"https://paperswithcode.com/method/fsaf"},"syntology_read_at":"2026-09-24T18:15:14+00:00"}