Democracy is crucial to a cryptocurrency ecosystem, as the diversity of miners (farms, personal computers, web clients, or even cloud functions) underlays the credibility of the cryptocurrency. Among miners, web clients used to be the vast majority, e.g., 50M+ as of March 2018. As time went on, however, cryptomining was gradually monopolized by mining farms with dedicated hardware (e.g., ASICs), and web clients scaled down to ∼0.1M. To suppress mining farms, certain cryptocurrencies (like Monero) adopted new mining algorithms such as RandomX whose execution relies on general-purpose hardware architectures. Unfortunately, this further impairs web-based cryptomining as web clients cannot provide the desired architecture support to these algorithms. This paper explores how to revive software democracy of efficient web-based crypto-mining, using a novel program transformation technique termed Vectra. Vectra employs just-in-time (JIT) transformations of mining programs for web architectures; it effectively identifies and merges isomorphic instructions upon execution. Vectra ensures correct transformations based on symbolic constraints of the instructions. Real-world deployments show that Vectra reduces WASM instructions by about 7× and achieves a 3× –16× speedup for web cryptomining in diverse execution environments like PCs, mobile phones, and serverless platforms, which translates to a high (69%–274%) return-on-investment (ROI) for common users.

Smart oceanic exploration has greatly benefitted from AI-driven underwater image and video processing. However, the volume of underwater video content is subject to narrow-band and time-varying underwater acoustic channels. How to support high-utility video transmission at such a limited capacity is still an open issue. In this paper, we propose a Flexible Underwater Video Codec (FUVC) with separate designs for targets-of-interest regions and backgrounds. The encoder locates all targets-of-interests, compresses their corresponding regions with x.265 and if bandwidth allows, compresses the background with a lower bitrate. The decoder reconstructs both streams, identifies clean targets-of-interest and fuses them with the background via a Mask Detection and Background Recovery (MDBR) network. When the background stream is unavailable, the decoder adapts all targets-of-interest to a virtual background via Poisson blending. Experimental results show that FUVC outperforms other codecs with a lower bitrate at the same quality. It also supports a flexible codec for underwater acoustic channels. The database and source code are available at https://github.com/z21110008/FUVC.

Due to complex and volatile lighting environment, underwater imaging can be readily impaired by light scattering, warping, and noises. To improve the visual quality, Underwater Image Enhancement (UIE) techniques have been widely studied. Recent efforts have also been contributed to evaluate and compare the UIE performances with subjective and objective methods. However, the subjective evaluation is time-consuming and uneconomic for all images, while existing objective methods have limited capabilities for the newly-developed UIE approaches based on deep learning. To fill this gap, we propose an Underwater Image Fidelity (UIF) metric for objective evaluation of enhanced underwater images. By exploiting the statistical features of these images in CIELab space, we present the naturalness, sharpness, and structure indexes. Among them, the naturalness and sharpness indexes represent the visual improvements of enhanced images; the structure index indicates the structural similarity between the underwater images before and after UIE. We combine all indexes with a saliency-based spatial pooling and thus obtain the final UIF metric. To evaluate the proposed metric, we also establish a first-of-its-kind large-scale UIE database with subjective scores, namely Underwater Image Enhancement Database (UIED). Experimental results confirm that the proposed UIF metric outperforms a variety of underwater and general-purpose image quality metrics. The database and source code are available at https://github.com/z21110008/UIF.

Classification remains challenging when confronted with the existence of multi-view data with limited labels. In this paper, we propose an embedding regularizer learning scheme for multi-view semi-supervised classification (ERL-MVSC). The proposed framework integrates diversity, sparsity and consensus to dexterously manipulate multi-view data with limited labels. To encourage diversity, ERL-MVSC recasts a linear regression model to derive view-specific embedding regularizers and automatically determines their weights. This is able to tactfully incorporate complementary information of different views. To ensure sparsity, ERL-MVSC imposes$\ell _{2,1}$-norm on a fused embedding regularizer to exploit the sparse local structure of samples, thereby conveying valuable classification information and enhancing the robustness against noise/outliers. To enhance consensus, ERL-MVSC learns a shared predicted label matrix, which serves as the comment target of multi-view classification. With these techniques, we formulate ERL-MVSC as a joint optimization problem of an embedding regularizer and a predicted label matrix, which can be solved by a coordinate descent method. Extensive experimental results on real-world datasets demonstrate the effectiveness and superiority of the proposed algorithm.