Deep semantic space with intra-class low-rank constraint for cross-modal retrieval

In this paper, a novel Deep Semantic Space learning model with Intra-class Low-rank constraint (DSSIL) is proposed for crossmodal retrieval, which is composed of two subnetworks for modality-specific representation learning, followed by projection layers for common space mapping. In particular, DSSIL takes into account semantic consistency to fuse the cross-modal data in a high-level common space, and constrains the common representation matrix within the same class to be low-rank, in order to induce the intra-class representations more relevant. More formally, two regularization terms are devised for the two aspects, which have been incorporated into the objective of DSSIL. To optimize the modality-specific subnetworks and the projection layers simultaneously by exploiting the gradient decent directly, we approximate the nonconvex low-rank constraint by minimizing a few smallest singular values of the intra-class matrix with theoretical analysis. Extensive experiments conducted on three public datasets demonstrate the competitive superiority of DSSIL for cross-modal retrieval compared with the state-of-theart methods.