Based on three OpenMP program models, the technology of parallel region reconstruction is mainly discussed to implement the improved loop level OpenMP program. parallel region reconstruction is to expand and merge par...
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How to design a low-latency and accurate approach for user behavior anomaly detection over data streams has become a great challenge. However, existing studies cannot meet low-latency and accurate requirements, due to...
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ISBN:
(纸本)9781509050819
How to design a low-latency and accurate approach for user behavior anomaly detection over data streams has become a great challenge. However, existing studies cannot meet low-latency and accurate requirements, due to a large number of subsequences and sequential relationship in behaviors. This paper presents BADSM, a user behavior anomaly detection approach based on sequence milling over data streams that seeks to address such challenge. BADSM uses self-adaptive behavior pruning algorithm to adaptively divide data stream into behaviors and decrease the number of subsequences to improve the efficiency of sequence mining. Meanwhile, the top-k abnormal scoring algorithm is used to reduce the complexity of traversal and obtain quantitative detection result to improve accuracy. We design and implement a streaming anomaly detection system based on BADSM to perform online detection. Extensive experiments confirm that BADSM significantly reduces processing delay by at least 36.8% and false positive rate by 6.4% compared with the classic sequence mining approach PrefixSpan.
We consider the distributed setting of K = (k + 1) x (k + 1) autonomous mobile robots operating on a grid graph of N = (n + 1) x (n + 1) nodes with n = k center dot d, d = 2, k = 2, following Look-Compute-Move cycles ...
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ISBN:
(纸本)9781450360944
We consider the distributed setting of K = (k + 1) x (k + 1) autonomous mobile robots operating on a grid graph of N = (n + 1) x (n + 1) nodes with n = k center dot d, d = 2, k = 2, following Look-Compute-Move cycles and communicating with other robots using colored lights under the robots with lights model. We consider the uniform scattering problem of repositioning the robots on the nodes of the grid graph so that each robot reach to a static configuration in which they cover uniformly the grid. In this paper, we provide the first O(n) time algorithm for this problem for robots with lights in the fully synchronous setting, given that the robots have the common orientation, the knowledge of parameters n and k, and the visibility range of distance 2d. The best previously known algorithm solves this problem in O(N/d) (i.e., O(n(2)/d)) time under the classic oblivious robots model (with no lights) with the same capabilities in the asynchronous setting. Our algorithm is asymptotically time-optimal, since for any solution to this uniform scattering problem in both the classic and lights models, O(n) time is necessary. Moreover, the proposed algorithm is collision-free.
This paper introduces PapyrusKV, a parallel embedded key-value store (KVS) for distributed high-performance computing (HPC) architectures that offer potentially massive pools of nonvolatile memory (NVM). PapyrusKV. st...
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ISBN:
(数字)9781450351140
ISBN:
(纸本)9781450351140
This paper introduces PapyrusKV, a parallel embedded key-value store (KVS) for distributed high-performance computing (HPC) architectures that offer potentially massive pools of nonvolatile memory (NVM). PapyrusKV. stores keys with their values in arbitrary byte arrays across multiple NVMs in a distributed system. PapyrusKV provides standard KVS operations such as put, get, and delete. More importantly, PapyrusKV provides advanced features for HPC such as dynamic consistency control, zero-copy workflow, and asynchronous checkpoint/restart. Beyond filesystems, PapyrusKV provides HPC programmers with a high-level interface to exploit distributed NVM in the system, and it transparently organizes data to achieve high performance. Also, it allows HPC applications to specialize PapyrusKV to meet their specific requirements. We empirically evaluate PapyrusKV on three HPC systems with real NVM devices: OLCF's Summitdev, TACC's Stampede, and NERSC's Cori. Our results show that PapyrusKV can offer high performance, scalability, and portability across these various distributed NVM architectures.
In a distributed generation system, the phase-locked loop (PLL) have a crucial impact on the transient stability of the grid-connected voltage source converters (VSCs). This paper discusses the instability mechanism o...
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ISBN:
(纸本)9781538660546
In a distributed generation system, the phase-locked loop (PLL) have a crucial impact on the transient stability of the grid-connected voltage source converters (VSCs). This paper discusses the instability mechanism of PLL and the interaction between the PLLs in the parallelgrid-connected inverter system. The dynamic characteristics of PLL considering the coupling of grid impedance and line impedance in weak grid are given in this paper. It is proposed that the movement of the steady-state operating point of the PLL will bring it closer to the unstable point under the disturbance. Due to the nonlinear characteristics of the PLL, the phase portrait is applied to distinguish the transient stability of the multi-PLL system. It is shown that the transient stability of system is deduced due to the PLL interaction in a multi-VSC system. The effects of inverter injection current, grid impedance and line impedance are discussed. Finally, the conclusions of this paper are verified by simulation comparison.
The continuous shift of hardware computing architectures, from single to many-core processors, as well as the blurring of the hardware - software interface, has made the introduction of parallel and distributed comput...
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ISBN:
(纸本)9783030105495;9783030105488
The continuous shift of hardware computing architectures, from single to many-core processors, as well as the blurring of the hardware - software interface, has made the introduction of parallel and distributedcomputing topics in the undergraduate curriculum an essential requirement for any quality computer science program. The University Politehnica of Bucharest offers a unique approach, employing a heterogeneous hardware and software teaching and computing infrastructure, to its over 450 students enrolled in undergraduate studies of Computer Science and Electrical Engineering. In this study we present two of the most important lectures covering PDC topics at the UPB.
gridcomputing promotes resource sharing, dynamic computational resource allocation, distributed data access from disjoint application domains and allowing various service providers to meet different demands efficient...
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ISBN:
(纸本)9781479938377
gridcomputing promotes resource sharing, dynamic computational resource allocation, distributed data access from disjoint application domains and allowing various service providers to meet different demands efficiently. With an increase of user demands to the resources, planning the guaranteed Quality of Service (QoS) is a challenging task. The objective of this paper is to propose an agent based grid framework and QoS Time Based Scheduling (QTBS) algorithm for effective task scheduling in the gridcomputing paradigm. This algorithm is simulated in the gridSim toolkit and the results shows that the proposed work gives better results in makespan, resource utilization rate and load balancing level than algorithms such as QoS guided Weighted Mean Time Min (QWMTM), QoS guided MinMin, Max-Min and Min-Min heuristic algorithms.
Due to avoiding the inherent escrow of identity-based cryptography and yet not requiring certificates to guarantee the authenticity of public keys, Li et al. proposed a certificateless proxy signature scheme from bili...
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ISBN:
(纸本)0769529097
Due to avoiding the inherent escrow of identity-based cryptography and yet not requiring certificates to guarantee the authenticity of public keys, Li et al. proposed a certificateless proxy signature scheme from bilinear pairings. As for the security, they claimed their scheme satisfies the security requirements of proxy signature such as strong identifiability, verifiability strong undeniabilty, preventions of misuse, and strong unforgeability;and any third party who can even get the signed warrant generated by the original signer can not forge a proxy signature. In this paper, however, we successfully identify a forgery attack against their scheme. That is, based on the proxy signature generated by a proxy signer on a message on behalf of an original signer, an adversary can forge a valid proxy signature on the same message which seemed generated by the proxy signer on behalf of this adversary himself After production a forged proxy signature, the adversary has the same authority with the original signer to the proxy signer, and the verifier cannot distinguish which one is the real original signer. To thwart this attacks, an improvement is further proposed.
Graphs are a natural fit for modeling concepts used in solving diverse problems in science, commerce, engineering, and governance. Responding to the variety of graph data and algorithms, many parallel and distributed ...
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ISBN:
(纸本)9781538658154
Graphs are a natural fit for modeling concepts used in solving diverse problems in science, commerce, engineering, and governance. Responding to the variety of graph data and algorithms, many parallel and distributed graph-processing systems exist. However, until now these platforms use a static model of deployment: they only run on a pre-defined set of machines. This raises many conceptual and pragmatic issues, including misfit with the highly dynamic nature of graph processing, and could lead to resource waste and high operational costs. In contrast, in this work we explore a dynamic, elastic model of deployment. To conduct an in-depth elasticity study of distributed graph processing, we build a prototype, JoyGraph, which is the first such system that implements complex, policy-based, and fine-grained elasticity. Using the state-of-the-art LDBC Graphalytics benchmark and the SPEC Cloud Group's elasticity metrics, we show the benefits of elasticity in graph processing: improved resource utilization, and aligned operation-workload dynamicity. Furthermore, we explore the cost of elasticity in graph processing. We identify a key drawback: although elasticity does not degrade application throughput, graph-processing workloads are sensitive to data movement while leasing or releasing resources.
Unstructured grids lead to unstructured communication on distributed memory parallel computers, a problem that has been considered difficult. Here, we consider adaptive, offline communication routing for a SIMD proces...
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Unstructured grids lead to unstructured communication on distributed memory parallel computers, a problem that has been considered difficult. Here, we consider adaptive, offline communication routing for a SIMD processor grid. Our approach is empirical. We use large data sets drawn from supercomputing applications instead of an analytic model of communication load. The chief contribution of this paper is an experimental demonstration of the effectiveness of certain routing heuristics. Our routing algorithm is adaptive, nonminimal, and is generally designed to exploit locality. We have a parallel implementation of the router, and we report on its performance.
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