Google brain nas-fpn outperforms sota models for object detection

Current state-of-the-art convolutional architectures for object detection tasks are human-designed. In a recent paper, Google Brain researchers leveraged the advantages of Neural

Architecture Search (NAS) to propose NAS-FPN, a new automatic search method for feature pyramid architecture. NAS-FPN achieves a better accuracy and latency tradeoff than current SOTA models

for object detection. From the paper’s abstract: > _“Here we aim to learn a better architecture of feature pyramid > network for object detection. We adopt Neural Architecture Search

> and discover a new feature pyramid architecture in a novel scalable > search space covering all cross-scale connections. The discovered > architecture, named NAS-FPN, consists of 

a combination of top-down > and bottom-up connections to fuse features across scales. NAS-FPN, > combined with various backbone models in the RetinaNet framework, > achieves better 

accuracy and latency tradeoff compared to > state-of-the-art object detection models. NAS-FPN improves mobile > detection accuracy by 2 AP compared to state-of-the-art SSDLite with

> MobileNetV2 model in [32] and achieves 48.3 AP which surpasses Mask > R-CNN [10] detection accuracy with less computation time.” > (arXiv)._ SYNCED INVITED DR. DAWEI DU, A

POSTDOCTORAL RESEARCHER AT THE STATE UNIVERSITY OF NEW YORK WITH A RESEARCH FOCUS ON VISUAL TRACKING, OBJECT DETECTION AND VIDEO SEGMENTATION APPLICATIONS, TO SHARE HIS THOUGHTS ON GOOGLE

BRAIN’S NAS-FPN. _HOW WOULD YOU DESCRIBE NAS-FPN?_ FPN is a pyramid representation for deep learning that combines low-resolution but strong semantic features and weak semantic but

high-resolution features via top-down and lateral connections. Moreover, NAS-FPN is an automatic neural architecture search algorithm that focuses on finding optimal connections between

different layers for pyramidal representations. Specifically, the RNN controller is trained to select the best architecture using reinforcement learning. First the child networks are sampled

by combining any two different layers. Then the accuracy score is regarded as the _reward_ of reinforcement learning to calculate the policy gradient to update the parameters of the

controller. During the training iterations, it is possible to generate the structure with better accuracy via the controller. Experiments on the COCO test set show the proposed method

achieves considerable accuracy improvement compared to existing object detection models, e.g., MobileNetV2, and RetinaNet. _WHY DOES THIS RESEARCH MATTER?_ Deep learning dominates various

tasks in computer vision. However, the majority of the previous works focuses on training the parameters of networks in human-designed architectures. Recently, there has been increasing

interest in designing the structure of neural networks automatically. Xie et al. explored randomly wired neural networks for image recognition. Liu et al. proposed searching the network

level structure in addition to the cell level structure for semantic segmentation. Differing from the aforementioned work, this paper provides another research direction that makes it

possible to search the optimal cross-layer connections to achieve discriminative multiscale feature representation of neural networks. _WHAT IMPACT MIGHT THIS RESEARCH BRING TO THE RESEARCH

COMMUNITY?_ Combing multi-scale features from different layers is one of the important techniques in deep learning for effectively improving the performance of many computer vision tasks.

However, the previously proposed human-designed structures may be not optimal, resulting in limited performance. Inspired by NAS-FPN, researchers can transfer the optimal network structures

to related tasks such as visual tracking and semantic segmentation. _CAN YOU IDENTIFY ANY BOTTLENECKS IN THE RESEARCH?_ The computational complexity of NAS is extremely high (100 TPUs used

in this paper), especially for complex backbones (e.g., ResNet-101). Therefore, it is very difficult to follow for labs without many computational resources. Besides, we still know little

about the insights of the optimal network generated by the NAS method. Why such layer connection combinations achieve better performance than human-designed ones? Can we learn from the

network design and transfer to other tasks (e.g., tracking, segmentation and classification)? The interpretation of it remains unsolved due to the complex cross-layer connections. _CAN YOU

PREDICT ANY POTENTIAL FUTURE DEVELOPMENTS RELATED TO THIS RESEARCH?_ I believe there will be much work using the NAS method in the future. According to prior knowledge of a specific task,

researchers can reduce the NAS search space by pruning some unnecessary connections. Besides, some effective modules will be found based on similar connections of optimal networks in

different tasks. It is interesting to think about designing a network that considers the tradeoff between complexity and accuracy, especially in embedded systems with limited resources. The

paper_ NAS-FPN: Learning Scalable Feature Pyramid Architecture for Object Detection_ is on arXiv. ABOUT DR. DAWEI DU Dawei Du is a Postdoctoral Researcher with the Computer Science

Department at the University at Albany, State University of New York. He received his PhD from the University of the Chinese Academy of Sciences. His research mainly focuses on visual

tracking, object detection and video segmentation. He is organizing the “Vision meets Drones: A Challenge” Workshop conjunction with ICCV 2019. Read his recent research on automatic checkout

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