Deep Hashing Network for Unsupervised Domain Adaptation
Hemanth VenkateswaraJose EusebioShayok ChakrabortySethuraman Panchanathan
Introduces the Office-Home benchmark dataset and presents a deep hashing framework that learns transferable binary representations for accurate and storage-efficient unsupervised domain adaptation.
The article addresses the challenge of training deep neural networks for object recognition when labeled data is scarce in a target domain but available in a related source domain. This unsupervised domain adaptation problem is compounded by the need for efficient data storage and retrieval amid growing digital image collections. Hashing techniques offer compact binary codes for fast similarity search, yet prior methods have not integrated deep feature learning with domain adaptation for this setting.
The work introduces the Office-Home dataset, containing roughly 15,500 images across 65 categories from four visual domains, and proposes the Domain Adaptive Hashing (DAH) network. DAH replaces the final classification layer of a pre-trained VGG-F convolutional network with a hashing layer trained by three loss terms: a supervised loss that encourages similar hash codes for same-category source images, an unsupervised entropy loss that aligns unlabeled target images to source categories, and a multi-kernel maximum mean discrepancy term that reduces distribution shift across multiple network layers.
Experiments on the Office and Office-Home benchmarks show that DAH achieves the highest average classification accuracy on Office-Home (45.54 percent) among compared methods and remains competitive on Office. The learned 64-bit hash codes also yield higher mean average precision for retrieval than other unsupervised hashing approaches, with domain alignment visibly reducing feature discrepancy in t-SNE visualizations. Performance gains are larger when the number of categories is high.
These results indicate that jointly learning transferable hash codes and reducing domain shift within a single deep network improves both classification and retrieval under label scarcity. The framework is particularly useful for large-scale vision applications where annotation cost is high and storage efficiency matters. The new Office-Home dataset provides a more challenging testbed than prior collections for evaluating such methods.
Further validation on additional domains, larger hash lengths, and real-world deployment scenarios would strengthen confidence in the approach. The authors note that domain-adversarial training can outperform DAH when category counts are small, suggesting hybrid strategies may be worth exploring.
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