4 research outputs found
Unsupervised Hashing via Similarity Distribution Calibration
Existing unsupervised hashing methods typically adopt a feature similarity
preservation paradigm. As a result, they overlook the intrinsic similarity
capacity discrepancy between the continuous feature and discrete hash code
spaces. Specifically, since the feature similarity distribution is
intrinsically biased (e.g., moderately positive similarity scores on negative
pairs), the hash code similarities of positive and negative pairs often become
inseparable (i.e., the similarity collapse problem). To solve this problem, in
this paper a novel Similarity Distribution Calibration (SDC) method is
introduced. Instead of matching individual pairwise similarity scores, SDC
aligns the hash code similarity distribution towards a calibration distribution
(e.g., beta distribution) with sufficient spread across the entire similarity
capacity/range, to alleviate the similarity collapse problem. Extensive
experiments show that our SDC outperforms the state-of-the-art alternatives on
both coarse category-level and instance-level image retrieval tasks, often by a
large margin. Code is available at https://github.com/kamwoh/sdc