Few Shot Learning with a Strong Teacher
Few shot learning (FSL) aims to train a strong classifier using limited labeled examples. Many existing works take the meta learning approach, sampling few shot tasks in turn and optimizing the few shot learner's performance on classifying the query examples. In this paper, we point out two potential weaknesses of this approach. First, the sampled query examples may not provide sufficient supervision for the few shot learner. Second, the effectiveness of meta learning diminishes sharply with increasing shots (i.e. the number of training examples per class) To resolve these issues, we propose a novel objective to directly train the few shot learner to perform like a strong classifier. Concretely, we associate each sampled few shot task with a strong classifier, which is learned with ample labeled examples. The strong classifier has a better generalization ability and we use it to supervise the few shot learner. We present an efficient way to construct the strong classifier, making our proposed objective an easily plug and play term to existing meta learning based FSL methods. We validate our approach in combinations with many representative meta learning methods. On several benchmark datasets including mini ImageNet and tired ImageNet, our approach leads to a notable improvement across a variety of tasks. More importantly, with our approach, meta learning based FSL methods can consistently outperform non meta learning based ones, even in a many shot setting, greatly strengthening their applicability.
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