Social matching is a task that recommends potential friends to users based on their existing friendships. This user-to-user recommendation setting extends general recommender systems by shifting the focus from user-item interactions to interactions among users themselves, and general recommendation methods are often directly applied to this setting. However, we argue that in federated learning, directly applying existing federated recommendation methods to social matching can result in privacy leakage, due to the specificity of social matching: the mutual nature of friendships. We theoretically and quantitatively reveal these security vulnerabilities and propose a novel interaction-level membership inference attack targeting federated social matching. Our attack employs a reconstruction model combining affine transformations with an MLP to capture both linear and non-linear mappings between users' public and private embeddings. Trained on a portion of leaking user data, it can reconstruct benign users' private embeddings and infer their true friends. We conduct numerous experiments on multiple datasets under various experimental settings to verify the effectiveness and robustness of our attack method. Experimental results show that: (i) Our attack approach exhibits strong robustness and effectiveness across diverse experimental setups; (ii) Existing defense methods fail to effectively resist our attack while maintaining satisfactory recommendation performance. Our findings highlight the need for new privacy-preserving techniques specifically designed for federated social matching.

Brain-computer interfaces (BCIs) enable communication between the brain and the external environment, showing significant potential in restoration, rehabilitation and movement enhancement. However, neural drift causes BCI performance to degrade substantially over time, compromising their long-term reliability. A fundamental limitation of current methods is their failure to account for a key insight from neural preference theory that the magnitude of neural drift depends on specific motor parameters (e.g., velocity, direction, and speed), ultimately compromising performance. To overcome the limitation, we introduce a novel framework named ComplementaryDisentangled Neural Generalization (CDNG) inspired by neural preference theory. Specifically, we first conduct pre-experiments about the neural decoding preference, revealing that neural drifts differ across velocity, speed and direction. Then we adopt CDNG, which captures invariant neural representations through an ensemble of three specialized neural decoders after disentangling velocity into speed and direction. Extensive experiments on several datasets demonstrate that our method achieves state-of-the-art performance and significantly enhances cross-day generalization.

Cloud providers use SmartNIC-accelerated virtual switches (vSwitches) to offer rich network functions (NFs) for tenant VMs. Constrained by limited SmartNIC resources, it is a challenge to provide sufficient network performance for high-demand VMs. Meanwhile, we observed a significant number of idle vSwitches in the data center, which led us to consider leveraging them to build a remote resource pool for high-demand virtual NICs (vNICs). In this work, we propose Nezha, a distributed vSwitch load sharing system. Nezha reuses the existing idle SmartNICs to handle the excess load from the local SmartNIC without adding new devices. Nezha offloads stateless rule/flow tables to the remote, while keeping states locally. This eliminates the need for state synchronization, facilitating load sharing and failover. The deployment cost of Nezha is only a small fraction of that required to deploy new devices. Data collected from production show that our CPS capability bottleneck has shifted from the vSwitch to the VM kernel stack, with #concurrent flows and #vNICs increased by up to 50.4x and 40x, respectively.

The rapid expansion of decentralized finance (DeFi) applications has catalyzed the emergence of new blockchain systems at an unprecedented pace. However, these systems are largely evolving in isolation, hindering the development of a cohesive ecosystem where value and data can flow seamlessly across networks. Blockchain interoperability technologies are introduced to break down these communication barriers and facilitate effective interactions between different blockchain systems. In recent years, numerous approaches and solutions to blockchain interoperability have been proposed. While some reviews have attempted to categorize cross-chain solutions based on blockchain standards and architectures, a more in-depth analysis is warranted. In this work, we investigate mainstream cross-chain solutions from the perspective of their principles, applications, protocols, and performance. To clarify the concept of blockchain interoperability, we propose a conceptual model that characterizes both asset interoperability and data interoperability. Furthermore, we introduce a hierarchical architecture to categorize and analyze representative cross-chain solutions, covering both academic research and industrial implementations. To maximize the utility of this review for a wide audience, we also highlight open challenges and identify future directions in the field of blockchain interoperability, expecting to provide a comprehensive overview of cross-chain solutions.

Brain-computer interfaces (BCIs) offer a means to convert neural signals into control signals, providing a potential restoration of movement for people with paralysis. Despite their promise, BCIs face a significant challenge in maintaining decoding accuracy over time due to neural nonstationarities. While current recalibration techniques address this issue to a degree, they either fail to adequately exploit the limited labeled data, fail to perform conditional alignment in regression tasks, or overlook the signal correlation between data from two days. This paper proposes a novel Speed-enhanced Subdomain Alignment (SeSA) framework, integrating semi-supervised learning with domain adaptation techniques in regressive neural decoding. Specifically, SeSA carries out two alignments (i.e., global alignment and conditional speed alignment) to achieve recalibration. Our comprehensive set of experiments, both qualitative and quantitative, substantiate the superior recalibration performance and robustness of our proposed SeSA.

As blockchain smart contracts become more widespread and carry more valuable digital assets, they become an increasingly attractive target for attackers. Over the past few years, smart contracts have been subject to a plethora of devastating attacks, resulting in billions of dollars in financial losses. There has been a notable surge of research interest in identifying defects in smart contracts. However, existing smart contract fuzzing tools are still unsatisfactory. They struggle to screen out meaningful transaction sequences and specify critical inputs for each transaction. As a result, they can only trigger a limited range of contract states, making it difficult to unveil complicated vulnerabilities hidden in the deep state space. In this paper, we shed light on smart contract fuzzing by employing a sequence-aware mutation and seed mask guidance strategy. In particular, we first utilize data-flow-based feedback to determine transaction orders in a meaningful way and further introduce a sequence-aware mutation technique to explore deeper states. Thereafter, we design a mask-guided seed mutation strategy that biases the generated transaction inputs to hit target branches. In addition, we develop a dynamic-adaptive energy adjustment paradigm that balances the fuzzing resource allocation during a fuzzing campaign. We implement our designs into a new smart contract fuzzer named MuFuzz, and extensively evaluate it on three benchmarks. Empirical results demonstrate that MuFuzz outperforms existing tools in terms of both branch coverage and bug finding. Overall, MuFuzz achieves higher branch coverage than state-of-the-art fuzzers (up to 25%) and detects 30 % more bugs than existing bug detectors.

Apsara vSwitch (AVS) is a per-host deployed forwarding component for instance network connectivity in the Alibaba Cloud. To meet the growing performance demands, we accelerated AVS by adopting the most widely used "Sep-path" offloading architecture, which introduces a separate hardware data path to speed up popular traffic. However, the deployment results prove that it is difficult to bridge the gap in performance and programming flexibility of the software and hardware data paths, resulting in unpredictable performance and low iteration velocity.

Bitcoin is one of the decentralized cryptocurrencies powered by a peer-to-peer blockchain network. Parties who trade in the bitcoin network are not required to disclose any personal information. Such property of anonymity, however, precipitates potential malicious transactions to a certain extent. Indeed, various illegal activities such as money laundering, dark network trading, and gambling in the bitcoin network are nothing new now. While a proliferation of work has been developed to identify malicious bitcoin transactions, the behavior analysis and classification of bitcoin addresses are largely overlooked by existing tools. In this paper, we propose BAClassifier, a tool that can automatically classify bitcoin addresses based on their behaviors. Technically, we come up with the following three key designs. First, we consider casting the transactions of the bitcoin address into an address graph structure, of which we introduce a graph node compression technique and a graph structure augmentation method to characterize a unified graph representation. Furthermore, we leverage a graph feature network to learn the graph representations of each address and generate the graph embeddings. Finally, we aggregate all graph embeddings of an address into the address-level representation, and engage in a classification model to give the address behavior classification. As a side contribution, we construct and release a large-scale annotated dataset that consists of over 2 million real-world bitcoin addresses and concerns 4 types of address behaviors. Experimental results demonstrate that our proposed framework outperforms state-of-the-art bitcoin address classifiers and existing classification models, where the precision and F1-score are 96% and 95%, respectively. Our implementation and dataset are released, hoping to inspire others.

Over the past couple of years, smart contracts have been plagued by multifarious vulnerabilities, which have led to catastrophic financial losses. Their security issues, therefore, have drawn intense attention. As countermeasures, a family of tools has been developed to identify vulnerabilities in smart contracts at the source-code level. Unfortunately, only a small fraction of smart contracts is currently open-sourced. Another spectrum of work is presented to deal with pure bytecode, but most such efforts still suffer from relatively low performance due to the inherent difficulty in restoring abundant semantics in the source code from the bytecode.

Blockchain, a distributed and shared ledger, provides a credible and transparent solution to increase application auditability by querying the immutable records written in the ledger. Unfortunately, existing query APIs offered by the blockchain are inflexible and unscalable. Some studies propose off-chain solutions to provide more flexible and scalable query services. However, the query service providers (SPs) may deliver fake results without executing the real computation tasks and collude to cheat users. In this article, we propose a novel intelligent blockchain analytics platform termediQuery, in which we design a game theory based smart contract to ensure the trustworthiness of the query results at a reasonable monetary cost. Furthermore, the contract introduces the second opinion game that employs a randomized SP selection approach coupled with non-ordered asynchronous querying primitive to prevent collusion. We achieve a fixed price equilibrium, destroy the economic foundation of collusion, and can incentivize all rational SPs to act diligently with proper financial rewards. In particular,iQuerycan flexibly support semantic and analytical queries for generic consortium or public blockchains, achieving query scalability to massive blockchain data. Extensive experimental evaluations show thatiQueryis significantly faster than state-of-the-art systems. Specifically, in terms of the conditional, analytical, and multi-origin query semantics,iQueryis 2 ×, 7 ×, and 1.5 × faster than advanced blockchain and blockchain databases. Meanwhile, to guarantee 100% trustworthiness, only two copies of query results need to be verified iniQuery, whileiQuery's latency is$2 \sim 134$× smaller than the state-of-the-art systems.

Blockchain smart contracts have given rise to a variety of interesting and compelling applications and emerged as a revolutionary force for the Internet. Smart contracts from various fields now hold over one trillion dollars worth of virtual coins, attracting numerous attacks. Quite a few practitioners have devoted themselves to developing tools for detecting bugs in smart contracts. One line of efforts revolve around static analysis techniques, which heavily suffer from high false positive rates. Another line of works concentrate on fuzzing techniques. Unfortunately, current fuzzing approaches for smart contracts tend to conduct fuzzing starting from the initial state of the contract, which expends too much energy revolving around the initial state of the contract and thus is usually unable to unearth bugs triggered by other states. Moreover, most existing methods treat each branch equally, failing to take care of the branches that are rare or more likely to possess bugs. This might lead to resources wasted on normal branches. In this paper, we try to tackle these challenges from three aspects: 1) generating function invocation sequences, we explicitly consider data dependencies between functions to facilitate exploring richer states. We further prolong a function invocation sequence$\mathcal {S}_{1}$by appending a new sequence$\mathcal {S}_{2}$, so that the appended sequence$\mathcal {S}_{2}$can start fuzzing from states that are different from the initial state; 2) we incorporate a branch distance-based measure to evolve test cases iteratively towards a target branch; 3) we engage a branch search algorithm to discover rare and vulnerable branches, and design an energy allocation mechanism to take care of exercising these crucial branches. We implement IR-Fuzz and extensively evaluate it over 12K real-world contracts. Empirical results show that: (i) IR-Fuzz achieves 28% higher branch coverage than state-of-the-art fuzzing approaches, (ii) IR-Fuzz detects more vulnerabilities and increases the average accuracy of vulnerability detection by 7% over current methods, and (iii) IR-Fuzz is fast, generating an average of 350 test cases per second. Our implementation and dataset are released athttps://github.com/Messi-Q/IR-Fuzz, hoping to facilitate future research.

Recent years have witnessed explosive growth in blockchain smart contract applications. As smart contracts become increasingly popular and carry trillion dollars worth of digital assets, they become more of an appealing target for attackers, who have exploited vulnerabilities in smart contracts to cause catastrophic economic losses. Notwithstanding a proliferation of work that has been developed to detect an impressive list of vulnerabilities, the bad randomness vulnerability is overlooked by many existing tools. In this article, we make the first attempt to provide a systematic analysis of random numbers in Ethereum smart contracts, by investigating the principles behind pseudo-random number generation and organizing them into a taxonomy. We also lucubrate various attacks against bad random numbers and group them into four categories. Furthermore, we presentRNVulDet– a tool that incorporates taint analysis techniques to automatically identify bad randomness vulnerabilities and detect corresponding attack transactions. To extensively verify the effectiveness ofRNVulDet, we construct three new datasets: i) 34 well-known contracts that are reported to possess bad randomness vulnerabilities, ii) 214 popular contracts that have been rigorously audited before launch and are regarded as free of bad randomness vulnerabilities, and iii) a dataset consisting of 47,668 smart contracts and 49,951 suspicious transactions. We compareRNVulDetwith three state-of-the-art smart contract vulnerability detectors, and our tool significantly outperforms them. Meanwhile,RNVulDetspends 2.98 s per contract on average, in most cases orders-of-magnitude faster than other tools.RNVulDetsuccessfully reveals 44,264 attack transactions. Our implementation and datasets are released, hoping to inspire others.

Federated Recommendation (FR) has received con-siderable popularity and attention in the past few years. In FR, for each user, its feature vector and interaction data are kept locally on its own client thus are private to others. Without the access to above information, most existing poisoning attacks against recommender systems or federated learning lose validity. Benifiting from this characteristic, FR is commonly considered fairly secured. However, we argue that there is still possible and necessary security improvement could be made in FR. To prove our opinion, in this paper we present FedRecAttack, a model poisoning attack to FR aiming to raise the exposure ratio of target items. In most recommendation scenarios, apart from pri-vate user-item interactions (e.g., clicks, watches and purchases), some interactions are public (e.g., likes, follows and comments). Motivated by this point, in FedRecAttack we make use of the public interactions to approximate users' feature vectors, thereby attacker can generate poisoned gradients accordingly and control malicious users to upload the poisoned gradients in a well-designed way. To evaluate the effectiveness and side effects of FedRecAttack, we conduct extensive experiments on three real-world datasets of different sizes from two completely different scenarios. Experimental results demonstrate that our proposed FedRecAttack achieves the state-of-the-art effectiveness while its side effects are negligible. Moreover, even with small proportion (3%) of malicious users and small proportion (1%) of public interactions, FedRecAttack remains highly effective, which reveals that FR is more vulnerable to attack than people commonly considered.

Various attack methods against recommender systems have been proposed in the past years, and the security issues of recommender systems have drawn considerable attention. Traditional attacks attempt to make target items recommended to as many users as possible by poisoning the training data. Benifiting from the feature of protecting users' private data, federated recommendation can effectively defend such attacks. Therefore, quite a few works have devoted themselves to developing federated recommender systems. For proving current federated recommendation is still vulnerable, in this work we probe to design attack approaches targeting deep learning based recommender models in federated learning scenarios. Specifically, our attacks generate poisoned gradients for manipulated malicious users to upload based on two strategies (i.e., random approximation and hard user mining). Extensive experiments show that our well-designed attacks can effectively poison the target models, and the attack effectiveness sets the state-of-the-art.

Missing a security operation such as a bound check has been a major cause of security-critical bugs. Automatically checking whether the code misses a security operation in large programs is challenging since it has to understand whether the security operation is indeed necessary in the context. Recent methods typically employ cross-checking to identify deviations as security bugs, which collects functionally similar program slices and infers missed security operations through majority-voting. An inherent limitation of such approaches is that they heavily rely on a substantial number of similar code pieces to enable cross-checking. In practice, many code pieces are unique, and thus we may be unable to find adequate similar code snippets to utilize cross-checking.

Online deposit-free leasing service has witnessed rapid growth in China and shows a promising market in the future. While eliminating the requirement of a deposit does attract more users to the service, it also lowers the cost for fraudsters. Since the emergence of this service is relatively new, there are few works in literature focusing on detecting fraud transactions in it. Existing efforts mainly fall into hard-coded solutions such as block-listing or scorecard methods, which can be impotent in the face of the diverse fraud tactics, e.g., identity theft, or even suffering concept drift problem as the tactics evolve. In this paper, we contribute Turbo, an efficient graph-based anti-fraud system, to fully exploit the abundant user behavior logs in a real-time manner. Turbo is able to additionally make use of the implicit user relationships beyond the user features in the logs. To capture the user relationships, we first propose a novel algorithm to construct a time-evolving user behavior network called BN. Empirical analysis demonstrates that fraudsters in BN exhibit unique temporal aggregation and homophilic patterns, which inspires us to develop a novel heterogeneous adaptive graph neural network algorithm called HAG. Specifically, in HAG two graph operators are presented to mitigate the over-smoothing problem and make better use of the heterogeneous behavior relations in BN. Extensive experiments on a real-world dataset show that our method outperforms state-of-the-art methods significantly and can give a response in seconds for each detection request.

Smart contracts hold digital coins worth billions of dollars, their security issues have drawn extensive attention in the past years. Towards smart contract vulnerability detection, conventional methods heavily rely on fixed expert rules, leading to low accuracy and poor scalability. Recent deep learning approaches alleviate this issue but fail to encode useful expert knowledge. In this paper, we explore combining deep learning with expert patterns in an explainable fashion. Specifically, we develop automatic tools to extract expert patterns from the source code. We then cast the code into a semantic graph to extract deep graph features. Thereafter, the global graph feature and local expert patterns are fused to cooperate and approach the final prediction, while yielding their interpretable weights. Experiments are conducted on all available smart contracts with source code in two platforms, Ethereum and VNT Chain. Empirically, our system significantly outperforms state-of-the-art methods. Our code is released.

Rare classes are usually hidden in an imbalanced dataset with the majority of the data examples from major classes. Rare-class mining (RCM) aims at extracting all the data examples belonging to rare classes. Most of the existing approaches for RCM require a certain amount of labeled data examples as input. However, they are ineffective in practice since requesting label information from domain experts is time consuming and human-labor extensive. Thus, we investigate the unsupervised RCM problem, which to the best of our knowledge is the first such attempt. To this end, we propose an efficient algorithm called Fast-RCM for unsupervised RCM, which has an approximately linear time complexity with respect to data size and data dimensionality. Given an unlabeled dataset, Fast-RCM mines out the rare class by first building a rare tree for the input dataset and then extracting data examples of the rare classes based on this rare tree. Compared with the existing approaches which have quadric or even cubic time complexity, Fast-RCM is much faster and can be extended to large-scale datasets. The experimental evaluation on both synthetic and real-world datasets demonstrate that our algorithm can effectively and efficiently extract the rare classes from an unlabeled dataset under the unsupervised settings, and is approximately five times faster than that of the state-of-the-art methods.

Demand response (DR) has been widely adopted as a strategic plan of the electricity market in maintaining power grid reliability, sustainability, and stability. In a typical emergency DR (EDR) that arises in colocation data centers, participating tenants can reduce their power consumption when the supply of electricity is a shortage and be rewarded with financial compensation. In this paper, we study a mechanism design problem of motivating tenants for colocation EDR (MEDR). To solve the MEDR problem, we present a truthful Fully Polynomial-Time Approximation Scheme (FPTAS) which is theoretically proved deterministic, truthful and near-optimal, and can be approximated within 1 + ϵ for any given ϵ > 0, while the running time is in the polynomial of the number of tenants n and ε. To speed up the calculation of the payments, we further study the Vickrey-Clarke-Groves (VCG) based mechanism. Moreover, we build a MEDR auction system (MEDRAS) and implement all mechanism algorithms for a colocation data center. Comprehensive and detailed experiments have been implemented to validate the efficiency of our proposed mechanisms.

The security problems of smart contracts have drawn extensive attention due to the enormous financial losses caused by vulnerabilities. Existing methods on smart contract vulnerability detection heavily rely on fixed expert rules, leading to low detection accuracy. In this paper, we explore using graph neural networks (GNNs) for smart contract vulnerability detection. Particularly, we construct a contract graph to represent both syntactic and semantic structures of a smart contract function. To highlight the major nodes, we design an elimination phase to normalize the graph. Then, we propose a degree-free graph convolutional neural network (DR-GCN) and a novel temporal message propagation network (TMP) to learn from the normalized graphs for vulnerability detection. Extensive experiments show that our proposed approach significantly outperforms state-of-the-art methods in detecting three different types of vulnerabilities.

Nowadays, the popularity of e-commerce has brought huge economic benefits to factories, third-party merchants, and e-commerce service providers. Driven by such huge economic benefits, malicious merchants attempt to promote items through inserting fraudulent purchases, fake review scores, and/or feedback, into them. Mitigating this threat is challenging due to the difficulty of obtaining internal e-commerce data, the variance of e-commerce services used by malicious merchants, and the reluctance of service providers in cooperation. In this paper, we present an efficient, platform-independent, and robust e-commerce fraud detection system, CATS, to detect frauds for different large-scale e-commerce platforms. We implement the design of CATS into a prototype system and evaluate this prototype on the world's popular e-commerce platform Taobao. The evaluation result on Taobao shows that CATS can achieve a high accuracy of 91% in detecting frauds. Based on this success, we then apply CATS on another large-scale e-commerce platforms, and again CATS achieves an accuracy of 96%, suggesting that CATS is very effective on real e-commerce platforms. Based on the cross-platform evaluation results, we conduct a comprehensive analysis on the reported frauds and reveal several abnormal yet interesting behaviors of those reported frauds. Our study in this paper is expected to shed light on defending against frauds for various e-commerce platforms.

Demand response (DR) is a vital means of electricity market in maintaining power grid reliability, sustainability and stability. DR can enable consumers (e.g. data centers) to reduce their electricity consumption when the supply of electricity is a shortage. The consumers will be rewarded if they reduce or shift some of their energy usage during peak hours. Aiming at solving the efficiency of DR, in this paper, we present MEDR, a mechanism on emergency DR in colocation data center. First, we formalize the MEDR problem and propose a dynamic programming to solve the optimization version of the problem. We then design a deterministic mechanism to solve the MEDR. We prove that our mechanism is truthful and it is an FPTAS, i.e., it can be approximated within 1 + ε for any given ε > 0, while the running time of our mechanism is polynomial in the number of tenants n and 1/ε. Furthermore, we also give an auction system covering the efficient FPTAS algorithm as bidding decision program for DR. Finally, we choose a real dataset to build a large number of simulation datasets in performance evaluation. The results show that our mechanism outperforms near-optimal and high utility demonstrate the effectiveness of our work.

Nowadays, e-commerce has become prevalent world-wide. With the big success of e-commerce, many malicious promotion services also rise: with the goal of increasing sales, malicious merchants attempt to promote their target items by illegally optimizing the search results using fake visits, purchases, etc. In this paper, we study the fraud detection problem on large-scale e-commerce platforms. First, we develop an efficient and scalable AnTi-Fraud system (ATF) to detect e-commerce frauds for large-scale e-commerce platforms, and implement it in parallel on a large-scale computing platform, called Open Data Processing Service (ODPS). Then, we evaluate ATF using two real large-scale e-commerce datasets (with tens of millions users and items). The results demonstrate that both the precision and the recall of ATF can achieve 0.97+, which suggests that ATF is very effective. More importantly, we deploy ATF on the Taobao platform of Alibaba, which is one of the world's largest e-commerce platforms. The evaluation results show that ATF can also achieve an accuracy of 98.16% on Taobao, which again suggests that ATF is very effective and deployable in practice. Our study in this paper is expected to shed light on defending against online frauds for practical e-commerce platforms.

Community Question Answering (CQA) websites have become valuable knowledge repositories. Millions of internet users resort to CQA websites to seek answers to their encountered questions. CQA websites provide information far beyond a search on a site such as Google due to (1) the plethora of high-quality answers, and (2) the capabilities to post new questions toward the communities of domain experts. While most research efforts have been made to identify experts or to preliminarily detect potential experts of CQA websites, there has been a remarkable shift toward investigating how to keep the engagement of experts. Experts are usually the major contributors of high-quality answers and questions of CQA websites. Consequently, keeping the expert communities active is vital to improving the lifespan of these websites. In this article, we present an algorithm termed PALP to predict the activity level of expert users of CQA websites. To the best of our knowledge, PALP is the first approach to address a personalized activity level prediction model for CQA websites. Furthermore, it takes into consideration user behavior change over time and focuses specifically on expert users. Extensive experiments on the Stack Overflow website demonstrate the competitiveness of PALP over existing methods.

Hybrid-copy migration is a practical mean in cloud computing for memory intensive workload. But it does not perform perfectly in fetching remote pages. Aiming at solving this problem, we present a hot-page hybrid-copy migration method. We design a hot-page capturer to find out hot-pages, and a hot-page syringe to push hot-pages into transmission queue. We present an evaluation called page fault interval time, to evaluate the performance of hybrid-copy migration. The experimental results show that our method can extend the free part in page fault interval time about 19.79%, reduce the amount of remote page faults about 9.6%, and finally improve the performance of hybrid-copy migration.

When the applications are running in the virtual machine (VM), the virtual address of VM are translated into physical address in host. To improve the quality of address translation, huge page mechanism is introduced to increase Translation Lookaside Buffer (TLB) hit rates and reduce page faults. In this paper, we discuss and investigate the impact ofTHP(transparent huge page) on VM.

Rare category detecion (RCD) aims to discover rare categories in a massive unlabeled data set with the help of a labeling oracle. A challenging task in RCD is to discover rare categories which are concealed by numerous data examples from major categories. Only a few algorithms have been proposed for this issue, most of which are on quadratic or cubic time complexity. In this paper, we propose a novel tree-based algorithm known as RCD-Forest with $$O(\varphi n \log {(n/s)})$$ time complexity and high query efficiency where n is the size of the unlabeled data set. Experimental results on both synthetic and real data sets verify the effectiveness and efficiency of our method.

Mining arbitrary shaped clusters in large data sets is an open challenge in data mining. Various approaches to this problem have been proposed with high time complexity. To save computational cost, some algorithms try to shrink a data set size to a smaller amount of representative data examples. However, their user-defined shrinking ratios may significantly affect the clustering performance. In this paper, we present CLASP an effective and efficient algorithm for mining arbitrary shaped clusters. It automatically shrinks the size of a data set while effectively preserving the shape information of clusters in the data set with representative data examples. Then, it adjusts the positions of these representative data examples to enhance their intrinsic relationship and make the cluster structures more clear and distinct for clustering. Finally, it performs agglomerative clustering to identify the cluster structures with the help of a mutual k-nearest neighbors-based similarity metric called Pk. Extensive experiments on both synthetic and real data sets are conducted, and the results verify the effectiveness and efficiency of our approach.

Data sets collected from crowdsourcing platforms are well known for their cheap costs. But cheap costs may lead to low quality, i.e., labels may be incorrect or missing. Most of the existing work focuses on modeling the labeling errors of crowd workers, but missing labels can also cause problems when modeling the data. In this paper, we present an algorithm to predict the missing labels of crowd workers, in which we adopt thoughts from semi-supervised learning and utilize the particular consistency between crowd workers. We also define the consistency between workers by crowd labels and develop an algorithm to learn them from the data automatically. Experiments on both benchmark and real data show that our algorithm outperforms traditional semi-supervised learning algorithms in predicting missing labels, and the recovered crowd labels are capable of predicting the ground truth and reflecting real properties of crowd workers.

Commodity information such as prices and public reviews is always the concern of consumers. Helping them conveniently acquire these information as an instant reference is often of practical significance for their purchase activities. Nowadays, Web 2.0, linked data clouds, and the pervasiveness of smart hand held devices have created opportunities for this demand, i.e., users could just snap a photo of any commodity that is of interest at anytime and anywhere, and retrieve the relevant information via their Internet-linked mobile devices. Nonetheless, compared with the traditional keyword-based information retrieval, extracting the hidden information related to the commodities in photos is a much more complicated and challenging task, involving techniques such as pattern recognition, knowledge base construction, semantic comprehension, and statistic deduction. In this paper, we propose a framework to address this issue by leveraging on various techniques, and evaluate the effectiveness and efficiency of this framework with experiments on a prototype.

Browse with either web directories or social bookmarks is an important complementation to search by keywords in web information retrieval. To improve users' browse experiences and facilitate the web directory construction, in this paper, we propose a novel browse system called Social Web Directory (SWD for short) by integrating web directories and social bookmarks. In SWD, (1) web pages are automatically categorized to a hierarchical structure to be retrieved efficiently, and (2) the popular web pages, hottest tags, and expert users in each category are ranked to help users find information more conveniently. Extensive experimental results demonstrate the effectiveness of our SWD system.

Various solutions have been proposed to enable mobile users to access location-based services while preserving their location privacy. Some of these solutions are based on a centralized architecture with the participation of a trustworthy third party, whereas some other approaches are based on a mobile peer-to-peer (P2P) architecture. The former approaches suffer from the scalability problem when networks grow large, while the latter have to endure either low anonymization success rates or high communication overheads. To address these issues, this paper deals with an enhanced dual-active spatial cloaking algorithm (EDA) for preserving location privacy in mobile P2P networks. The proposed EDA allows mobile users to collect and actively disseminate their location information to other users. Moreover, to deal with the challenging characteristics of mobile P2P networks, e.g., constrained network resources and user mobility, EDA enables users (1) to perform a negotiation process to minimize the number of duplicate locations to be shared so as to significantly reduce the communication overhead among users, (2) to predict user locations based on the latest available information so as to eliminate the inaccuracy problem introduced by using some out-of-date locations, and (3) to use a latest-record-highest-priority (LRHP) strategy to reduce the probability of broadcasting fewer useful locations. Extensive simulations are conducted for a range of P2P network scenarios to evaluate the performance of EDA in comparison with the existing solutions. Experimental results demonstrate that the proposed EDA can improve the performance in terms of anonymity and service time with minimized communication overhead.

Virtualization technology has been widely applied in data centers and IT infrastructures, with advantages of server consolidation and live migration. Through live migration, data centers could flexibly move virtual machines among different physical machines to balance workloads, reduce energy consumption and enhance service availability.

The growth of server consolidation is due to virtualization technology that enables multiple servers to run on a single platform. However, virtualization may bring the overheads in performance. The prediction of virtualization performance is of especially important. The contribution of our paper is two-fold. First, we propose a general model to predict the performance of consolidation. Second, we study a load balancing problem that arises in server consolidation, where is to assign a number of workloads to a small number of high-performance target servers such that the workloads in each target servers are balancing. We first model the load balancing problem as an integer linear programming. Then, an fully polynomial time approximate scheme (FPTAS) is provided to get the near optimal solution. That is to say, for any given epsiv > 0, our algorithm achieves (1+epsiv)-approximation, and its running time is polynomial of both the number of source servers and 1/epsiv when the number of target servers and the dimensions are constants.

Computer supported cooperative work (CSCW) systems has the requirement of providing the communication architecture needed for groups of diverse users to cooperate in synchronous or asynchronous mode to achieve their common goals. CSCW environments have their own network supporting requirements. Due to the group and diverse QoS nature in CSCW communication, we think that deploying P2P architecture in CSCW is suitable and efficient. In this paper, we present a P2P architecture which support group forming, group awareness, data object distribution, session finding, QoS ensured multicasting in CSCW systems. A system named cooperative program understanding system (CPUS) which implements this architecture is also introduced

For constructing a cooperative learning environment, the authors propose a multimedia instruction model based on multi-agents and CSCW. The structure of the model and important technologies, such as the communication and control of agents, are discussed.