Many approaches to semantic image hashing have been formulated as supervised learning problems that utilize images and label information to learn the binary hash codes. However, large-scale labelled image data is expensive to obtain, thus imposing a restriction on the usage of such algorithms. On the other hand, unlabelled image data is abundant due to the existence of many Web image repositories. Such Web images may often come with images tags that contains useful information, although raw tags in general do not readily lead to semantic labels. Motivated by this scenario, we formulate the problem of semantic image hashing as a weakly-supervised learning problem. We utilize the information contained in the user-generated tags associated with the images to learn the hash codes. More specifically, we extract the word2vec semantic embeddings of the tags and use the information contained in them for constraining the learning. Accordingly, we name our model Weakly Supervised Deep Hashing using Tag Embeddings (WDHT). WDHT is tested for the task of semantic image retrieval and is compared against several state-of-art models. Results show that our approach sets a new state-of-art in the area of weekly supervised image hashing.
With the ever-increasing multimedia data on the Web, cross-modal video-text retrieval has received a lot of attention in recent years. Deep cross-modal hashing approaches utilize the Hamming space for achieving fast retrieval. However, most existing algorithms have difficulties in seeking or constructing a well-defined joint semantic space. In this paper, an unsupervised deep cross-modal video-text hashing approach (CLIP4Hashing) is proposed, which mitigates the difficulties in bridging between different modalities in the Hamming space through building a single hashing net by employing the pre-trained CLIP model [24]. The approach is enhanced by two novel techniques, the dynamic weighting strategy and the design of the min-max hashing layer, which are found to be the main sources of the performance gain. Compared with conventional deep cross-modal hashing algorithms, CLIP4Hashing does not require data-specific hyper-parameters. With evaluation using three challenging video-text benchmark datasets, we demonstrate that CLIP4Hashing is able to significantly outperform existing state-of-the-art hashing algorithms. Additionally, with larger bit sizes (e.g., 2048 bits), CLIP4Hashing can even deliver competitive performance compared with the results based on non-hashing features.
CCS CONCEPTS• Information systems → Multimedia and multimodal retrieval; Video search.
Federated Learning (FL) is a paradigm that aims to support loosely connected clients in learning a global model collaboratively with the help of a centralized server. The most popular FL algorithm is Federated Averaging (FedAvg), which is based on taking weighted average of the client models, with the weights determined largely based on dataset sizes at the clients. In this paper, we propose a new approach, termed Federated Node Selection (FedNS), for the server's global model aggregation in the FL setting. FedNS filters and reweights the clients' models at the node/kernel level, hence leading to a potentially better global model by fusing the best components of the clients. Using collaborative image classification as an example, we show with experiments from multiple datasets and networks that FedNS can consistently achieve improved performance over FedAvg.
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