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41.
András Faragó 《Algorithmica》2007,49(4):337-356
We prove two results that provide new fundamental limits for topology control in large ad hoc and sensor networks. First,
we show that it remains true under very general conditions that the maximum expected node degree must grow to infinity at
least logarithmically if we want to maintain asymptotic connectivity. This has been known so far only for much more special
models than ours. Building on this result, we prove a new fundamental limit regarding link dynamics, which means the worst case length ratio of the longest and shortest link adjacent to the same node. We prove that if link
dynamics remains bounded, then no topology control algorithm can keep a large network connected with high probability. Moreover,
bounded link dynamics prevents connectivity in the limit without any a priori assumption on node degrees or transmission ranges.
Our results hold in a model that is much more general than the frequently used assumption of uniformly distributed nodes in
a regularly shaped planar domain. Our more abstract setting also aims at finding (hopefully) more robust and elegant proofs
that have less dependence on the special geometry. Since link dynamics is expected to be bounded in practice, the results
strenghten the theoretical basis for the argument that a very large ad hoc or sensor network is unable to maintain connectivity
if it has a flat, random organization without additional structure.
Supported in part by NSF Grants ANI-0220001 and CCF-0634848. 相似文献
42.
Jung-Sheng Fu 《Information Sciences》2006,176(7):759-771
The hypercube is one of the most versatile and efficient interconnection networks (networks for short) so far discovered for parallel computation. Let f denote the number of faulty vertices in an n-cube. This study demonstrates that when f ? n − 2, the n-cube contains a fault-free path with length at least 2n − 2f − 1 (or 2n − 2f − 2) between two arbitrary vertices of odd (or even) distance. Since an n-cube is a bipartite graph with two partite sets of equal size, the path is longest in the worst-case. Furthermore, since the connectivity of an n-cube is n, the n-cube cannot tolerate n − 1 faulty vertices. Hence, our result is optimal. 相似文献
43.
本文首先根据三角模概念,定义了一类新的更具普遍意义的广义AND/OR图.根据新定义的启发式函数h(n,x)以及广义AND/OR图的最佳解树之所有子树亦是最佳子解树的原理,提出了广义AND/OR图的自底向上的启发式搜索算法BHAO.文中证明了算法BHAO的可采纳性.本文还提出了两类新的启发式函数的单调限制概念,并据此研究了算法BHAO的单调限制性质,研究了两个BHAO算法间的比较性质. 相似文献
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46.
《International Journal of Parallel, Emergent and Distributed Systems》2012,27(1-3):165-184
The purpose of this paper is to examine the impact of scheduling parallel tasks onto non-uniform memory access (NUMA) shared-memory multiprocessor systems by considering non-negligible intertask communications and communication contentions. Communication contentions arise from the communication medium having insufficient capacity to serve all transmissions, thereby causing significant contention delays. Therefore, a new scheduling algorithm, herein referred to as the Extended Critical Path (ECP) algorithm is proposed. The proposed algorithm schedules parallel tasks by considering non-negligible intertask communications and the contentions among shared communication resources. Moreover, it ensures performance within a factor of two of the optimum for general directed acyclic task graphs (DATGs). Experimental results demonstrate the superiority of the ECP algorithm over the scheduling algorithms presented in previous literature. 相似文献
47.
《International Journal of Parallel, Emergent and Distributed Systems》2012,27(1-3):185-203
CASS is a task management system that provides facilities for automatic grain-size optimization and task scheduling of parallel programs on distributed memory parallel architectures. The heart of CASS is a clustering module that partitions the tasks of a program into clusters that match the granularity of the target machine. This paper describes the clustering algorithms used by CASS and compares them with the best known algorithms reported in the literature, namely the PY algorithm (for clustering with task duplication) and the DSC algorithm (for clustering with no task duplication). It is shown that the clustering algorithms used by CASS outperform both the PY and DSC algorithms in terms of both speed and solution quality. 相似文献
48.
《International Journal of Parallel, Emergent and Distributed Systems》2012,27(4):305-320
Given a set S of n proper circular arcs, it is required to identify a largest cardinality subset K[S] of S each two of whose members intersect. This paper describes an optimal parallel algorithm to compute K[S]. The algorithm is not based on any previously known sequential solution, and is designed for the CREW PRAM model of computation. It uses 0(n/logn) processors and runs in O(logn) time. An interesting feature of the algorithm is that it transforms the computational geometric problem at hand, to a problem involving computations on 0-1 matrices, and then transforms the latter back into a ray shooting problem in computational geometry. 相似文献
49.
无线传感器网络随节点移动组成自我维持的自组织系统,采用连通支配集的虚拟骨干技术可使平面网络系统层次化而简化节点路由、管理和维护。但大规模无线传感器网络的连通支配集节点数目依然庞大,d-hop连通支配集可以大大减小支配集节点数目。另外,由于存在节点失效、链路断裂等无线特性,虚拟骨干网需要具备一定的容错性。在单位圆盘图网络模型中为构建精简且具有容错能力的虚拟骨干网,提出d-hop 2-连通支配集的分布式构造算法,先构造d-hop独立支配集后再连通形成d-hop 2-连通支配集。并从理论和仿真上对算法的复杂度、近似比和算法性能作了进一步探讨和验证。 相似文献
50.