Hashing has been widely researched to solve the large-scale approximate nearest neighbor search problem owing to its time and storage superiority. In recent years, a number of online hashing methods have emerged, which can update the hash functions to adapt to the new stream data and realize dynamic retrieval. However, existing online hashing methods are required to update the whole database with the latest hash functions when a query arrives, which leads to low retrieval efficiency with the continuous increase of the stream data. On the other hand, these methods ignore the supervision relationship among the examples, especially in the multi-label case. In this paper, we propose a novel Fast Online Hashing (FOH) method which only updates the binary codes of a small part of the database. To be specific, we first build a query pool in which the nearest neighbors of each central point are recorded. When a new query arrives, only the binary codes of the corresponding potential neighbors are updated. In addition, we create a similarity matrix which takes the multi-label supervision information into account and bring in the multi-label projection loss to further preserve the similarity among the multi-label data. The experimental results on two common benchmarks show that the proposed FOH can achieve dramatic superiority on query time up to 6.28 seconds less than state-of-the-art baselines with competitive retrieval accuracy.

Hashing based visual search has attracted extensive research Online hashing has attracted extensive research attention attention in recent years due to the rapid growth of when facing streaming data. Most online hashing visual data on the Internet [7, 33, 8, 26, 12, 13, 30, 32, 25, methods, learning binary codes based on pairwise similarities 35, 27]. In various scenarios, online hashing has become of training instances, fail to capture the semantic relationship, a hot topic due to the emergence of handling the streaming and suffer from a poor generalization in largescale data, which aims to resolve an online retrieval task by applications due to large variations. In this paper, we updating the hash functions from sequentially arriving data propose to model the similarity distributions between the input instances. On one hand, online hashing takes advantages data and the hashing codes, upon which a novel supervised of traditional offline hashing methods, i.e., low storage cost online hashing method, dubbed as Similarity Distribution and efficiency of pairwise distance computation in the Hamming based Online Hashing (SDOH), is proposed, to keep space. On the other hand, it also merits in training the intrinsic semantic relationship in the produced Hamming efficiency and scalability for large-scale applications, since space. Specifically, we first transform the discrete the hash functions are updated instantly and solely based on similarity matrix into a probability matrix via a Gaussianbased the current streaming data, which is superior to traditional normalization to address the extremely imbalanced hashing methods based on a hashing model entirely trained distribution issue. And then, we introduce a scaling Student from scratch.

Hash function learning has been recently received more and more attentions in fast search for large scale data. However, existing popular learning based hashing methods are batch-based learning models and thus incur large scale computational problem for learning an optimal model on a large scale of labelled data and cannot handle data which comes sequentially. In this paper, we address the problem by developing an online hashing learning algorithm to get hashing model accommodate to each new pair of data. At the same time the new updated hash model is penalized by the last learned model in order to retain important information learned in previous rounds. We also derive a tight bound for the cumulative loss of our proposed online learning algorithm. The experimental results demonstrate superiority of the proposed online hashing model on searching both metric distance neighbors and semantical similar neighbors in the experiments.