Deep Multiple Length Hashing via Multi-task Learning

Hashing can compress heterogeneous high-dimensional data into compact binary codes. For most existing hash methods, they first predetermine a fixed length for the hash code and then train the model based on this fixed length. However, when the task requirements change, these methods need to retrain the model for a new length of hash codes, which increases time cost. To address this issue, we propose a deep supervised hashing method, called deep multiple length hashing(DMLH), which can learn multiple length hash codes simultaneously based on a multi-task learning network. This proposed DMLH can well utilize the relationships with a hard parameter sharing-based multi-task network. Specifically, in DMLH, the multiple hash codes with different lengths are regarded as different views of the same sample. Furthermore, we introduce a type of mutual information loss to mine the association among hash codes of different lengths. Extensive experiments have indicated that DMLH outperforms most existing models, verifying its effectiveness.