Deep Distance Weighted Sampling Hashing for Cross-Modal Retrieval

Cross-modal hashing seeks to encode heterogeneous image-text data into compact binary codes for efficient retrieval. While significant efforts have been made to study sampling strategies, most of these approaches are tightly integrated with loss function engineering, lacking an independent focus on sampling methods. In this paper, we challenge the convention by revealing that batch-level sampling strategy is equally pivotal as loss design for learning discriminative hash codes. Specifically, by introducing a novel distribution-aware sampling strategy, a Distance Weighted Sampling Hashing (DDWSH) framework is proposed to dynamically select stable and informative training pairs. Unlike conventional random or semi-hard sampling, our method weights pairwise distances within each batch to approximate global data distribution, thereby mitigating training instability caused by biased sampling. To rigorously validate our claims, we conduct the first comprehensive crossover study between sampling strategies (random/semi-hard/ours) and loss functions (contrastive/triplet/ours) across three benchmark datasets. Experiments demonstrate that: Universality: Our sampling boosts all loss functions' performance (average +4.3% mAP vs. semi-hard mining), Superiority: DDWSH competes with complex loss function design and achieves state-of-the-art results, and Stability: It reduces performance variance by 60.2% compared to semi-hard sampling under varying batch compositions average. This systematic analysis establishes sampling as an independent research dimension in deep hashing, beyond a mere part of loss function engineering. The source code for DDWSH is freely available athttps://github.com/QinLab-WFU/DDWSH.