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991.
992.
The Vertical Block–cyclic Distributed Parallel LU Factorization Method (VBPLU) is effectively processed on a distributed memory parallel computer. VBPLU is based on the two techniques, the block algorithm and the aggregation of communications. Since startup time dominates the data communication and the aggregation reduces communication isssues, the total performance has been much improved. Furthermore this method uses long vectors so that it is also advantageous on vector processors. In this paper, we have constructed a modeling of VBPLU using a simplified LogGP model with analytical formulae, and estimated accurately the computational cost taking into account load distributions caused by data layout and process mapping. Some knowledge for optimization of block algorithm has been obtained. Our estimations have been verified through numerical experiments on three different distributed memory parallel computers. 相似文献
993.
994.
我国多数油田经过一次、二次采油后,仅能采出地下总储量的30%左右,这意味着有60%~70%的剩余石油仍然残留在地下成为剩余油。加强剩余油分布规律研究、提高石油采收率不仅有着可观的经济效应,而且关系到国家石油战略的安全。本研究应用神经网络的原理,基于BP网络使用MATLAB语言建立一个剩余油分布的预测系统。该系统通过学习在地理坐标和孔隙度之间建立一个非线性函数关系,以此来预测任何区域的孔隙度,再通过孔隙度与剩余油饱和度之间的关系达到剩余油分布预测的目的。 相似文献
995.
The paper offers an associative-neural-net method to optimize resource allocation between independent tasks in a multiprocessor
system. In the case of a dual-core CPU the method allows the task to be fully solved in O(M) operations.
The text was submitted by the authors in English. 相似文献
996.
997.
On basic properties of fault-tolerant multi-topology routing 总被引:1,自引:0,他引:1
Multi-topology routing has recently gained popularity as a simple yet efficient traffic engineering concept. Its basic purpose is to separate different classes of network traffic, which are then transported over disjoint logical topologies. Multi-topology routing is used as a basis for implementation of an IP fast reroute scheme called Multiple Routing Configurations (MRC).MRC has a range of attractive properties, but they do come at a cost. In order to guarantee recovery from any single link or node failure in the network, MRC has to maintain several logical topologies and thus an increased amount of routing information. The number of the logical topologies in MRC need not be large; even simple heuristic algorithms often yield good results in practice. However, why this is the case is not fully understood yet.In this paper, we introduce a theoretical framework for fault-tolerant multi-topology routing (FT-MTR). MRC is a practical implementation of FT-MTR in connectionless IP networks. We use FT-MTR to study how the internal topological structure of the communication network relates to two important problems. The first problem is minimizing the number of logical topologies and thus the routing state in FT-MTR. We show how to use the sets of nodes that separate the topology graph to devise an advanced heuristic for “intelligent” construction of the logical topologies. Finding the separating sets in a topology graph is computationally demanding; we present an algorithm that performs well in tested real network topologies. We evaluate the separation-set based heuristic for the logical topology construction and show that it outperforms the known MRC heuristics.The second problem is the FT-MTR load distribution after a failure. We use the separating sets to devise a novel algorithm for failure load distribution. This algorithm does not require knowledge of the traffic demand matrix, still, our tests indicate that it performs as good as, or better than, known MRC load-distribution algorithms that do require the demand matrix as input. 相似文献
998.
Prefetching in Content Distribution Networks via Web Communities Identification and Outsourcing 总被引:1,自引:0,他引:1
Antonis Sidiropoulos George Pallis Dimitrios Katsaros Konstantinos Stamos Athena Vakali Yannis Manolopoulos 《World Wide Web》2008,11(1):39-70
Content distribution networks (CDNs) improve scalability and reliability, by replicating content to the “edge” of the Internet.
Apart from the pure networking issues of the CDNs relevant to the establishment of the infrastructure, some very crucial data
management issues must be resolved to exploit the full potential of CDNs to reduce the “last mile” latencies. A very important
issue is the selection of the content to be prefetched to the CDN servers. All the approaches developed so far, assume the
existence of adequate content popularity statistics to drive the prefetch decisions. Such information though, is not always
available, or it is extremely volatile, turning such methods problematic. To address this issue, we develop self-adaptive
techniques to select the outsourced content in a CDN infrastructure, which requires no apriori knowledge of request statistics.
We identify clusters of “correlated” Web pages in a site, called Web site communities, and make these communities the basic outsourcing unit. Through a detailed simulation environment, using both real and synthetic
data, we show that the proposed techniques are very robust and effective in reducing the user-perceived latency, performing
very close to an unfeasible, off-line policy, which has full knowledge of the content popularity. 相似文献
999.
Most existing solutions to group security in Mobile Ad Hoc Networks (MANETs) rely on a multicast Core Based Tree (CBT) for key distribution. Such solutions, although suitable for systems with low mobility and static characteristics, are unsuitable for dynamic and sparse groups with changing neighborhoods. In this paper, we propose an entirely decentralized key generation mechanism, employing a central trusted entity only during initialization. Using our approach, keys can be established between group members with absolutely no prior communication. The solution relies on threshold cryptography and introduces a novel concept of Node-Group-Key (NGK) mapping. We have provided an extensive analytical model for the computations involved and communication costs and have also provided a lie detection mechanism. Simulation results show appreciable performance improvement and enhanced robustness. 相似文献
1000.
货币识别技术利用各种传感器来检测和测量货币的各类信息,选择有效、精确的传感器是实现货币识别的第一步工作;在真币性质比较稳定,以及货币样本容易获取的现实条件下,讨论了真币性质的特性,提出了基于正态分布和向量范数的检测方法,它通过对货币样本数据的统计分析来判断传感器的有效性和精确性;此方法简洁实用,为传感器的选择提供了客观依据。 相似文献