Cross-Domain Few-Shot Classification via Dense-Sparse-Dense Regularization

This work addresses the problem of cross-domain few-shot classification which aims at recognizing novel categories in unseen domains with only a few labeled data samples. We think that the pre-trained model contains the redundant elements which are useless or even harmful for the downstream tasks. To remedy the drawback, we introduce an L²-SP regularized dense-sparse-dense (DSD) fine-tuning flow for regularizing the capacity of pre-trained networks and achieving efficient few-shot domain adaptation. Given a pre-trained model from the source domain, we start by carrying out a conventional dense fine-tuning step using the target data. Then we execute a sparse pruning step that prunes the unimportant connections and fine-tunes the weights of sub-network. Finally, initialized with the fine-tuned sub-network, we retrain the original dense network as the output model for the target domain. The whole fine-tuning procedure is regularized by an L²-SP term. In contrast to the existing methods that either tune the weights or prune the network structure for domain adaptation, our regularized DSD fine-tuning flow simultaneously exploits the benefits of sparsity regularity and dense network capacity to gain the best of both worlds. Our method can be applied in a plug-and-play manner to improve the existing fine-tuning methods. Extensive experimental results on benchmark datasets demonstrate that our method in many cases outperforms the existing cross-domain few-shot classification methods in significant margins. Our code will be released soon.