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Dingyi Zhang

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3 papers

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IJCAI Conference 2022 Conference Paper

Masked Feature Generation Network for Few-Shot Learning

Yunlong Yu
Dingyi Zhang
Zhong Ji

In this paper, we present a feature-augmentation approach called Masked Feature Generation Network (MFGN) for Few-Shot Learning (FSL), a challenging task that attempts to recognize the novel classes with a few visual instances for each class. Most of the feature-augmentation approaches tackle FSL tasks via modeling the intra-class distributions. We extend this idea further to explicitly capture the intra-class variations in a one-to-many manner. Specifically, MFGN consists of an encoder-decoder architecture, with an encoder that performs as a feature extractor and extracts the feature embeddings of the available visual instances (the unavailable instances are seen to be masked), along with a decoder that performs as a feature generator and reconstructs the feature embeddings of the unavailable visual instances from both the available feature embeddings and the masked tokens. Equipped with this generative architecture, MFGN produces nontrivial visual features for the novel classes with limited visual instances. In extensive experiments on four FSL benchmarks, MFGN performs competitively and outperforms the state-of-the-art competitors on most of the few-shot classification tasks.

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IJCAI Conference 2022 Conference Paper

Multi-Proxy Learning from an Entropy Optimization Perspective

Yunlong Yu
Dingyi Zhang
Yingming Li
Zhongfei Zhang

Deep Metric Learning, a task that learns a feature embedding space where semantically similar samples are located closer than dissimilar samples, is a cornerstone of many computer vision applications. Most of the existing proxy-based approaches usually exploit the global context via learning a single proxy for each training class, which struggles in capturing the complex non-uniform data distribution with different patterns. In this work, we present an easy-to-implement framework to effectively capture the local neighbor relationships via learning multiple proxies for each class that collectively approximate the intra-class distribution. In the context of large intra-class visual diversity, we revisit the entropy learning under the multi-proxy learning framework and provide a training routine that both minimizes the entropy of intra-class probability distribution and maximizes the entropy of inter-class probability distribution. In this way, our model is able to better capture the intra-class variations and smooth the inter-class differences and thus facilitates to extract more semantic feature representations for the downstream tasks. Extensive experimental results demonstrate that the proposed approach achieves competitive performances. Codes and an appendix are provided.

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NeurIPS Conference 2020 Conference Paper

Deep Metric Learning with Spherical Embedding

Dingyi Zhang
Yingming Li
Zhongfei Zhang

Deep metric learning has attracted much attention in recent years, due to seamlessly combining the distance metric learning and deep neural network. Many endeavors are devoted to design different pair-based angular loss functions, which decouple the magnitude and direction information for embedding vectors and ensure the training and testing measure consistency. However, these traditional angular losses cannot guarantee that all the sample embeddings are on the surface of the same hypersphere during the training stage, which would result in unstable gradient in batch optimization and may influence the quick convergence of the embedding learning. In this paper, we first investigate the effect of the embedding norm for deep metric learning with angular distance, and then propose a spherical embedding constraint (SEC) to regularize the distribution of the norms. SEC adaptively adjusts the embeddings to fall on the same hypersphere and performs more balanced direction update. Extensive experiments on deep metric learning, face recognition, and contrastive self-supervised learning show that the SEC-based angular space learning strategy significantly improves the performance of the state-of-the-art.

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