【作者】 李运发；

【导师】 韩宗芬；

【作者基本信息】 华中科技大学 ， 计算机软件与理论， 2004， 硕士

【摘要】 对于分布式软件可靠性研究,在最初阶段,人们只是借鉴一般软件可靠性评估的基本理论和方法。随着软件可靠性评估技术的发展,形成了许多关于分布式软件可靠性评估的理论和方法,其中大部分是基于图论,利用K-端点网络因式分解定理进行评估。这种评估方法虽然经过理论分析和推导,具有一定的合理性,但是因其只考虑了分布式软件可靠性单项指标,没有综合分析分布式软件的其它性能对可靠性的影响,因此,在实际应用方面具有一定的局限性。针对上述局限性,“具有时间约束的分布式软件可靠性评估研究”以分布式软件的可靠性模型为基础,将精简和深度优先两种方法有机结合,引入时间约束因子,对分布式软件可靠性进行理论分析,确定具有时间约束的分布式软件可靠性评估的理论方法。在此基础上,推导出Degree-1精简算法、Series精简算法、新的文件生成树生成算法、文件传输路径生成算法以及响应时间评估算法。在使用这一系列算法之前,首先对分布式系统进行形式化描述,形成分布式系统示意图,为算法提供运用环境。根据节点上可用的数据文件和节点的度数,Degree-1精简算法和Series精简算法分别对分布式系统示意图进行度1精简和度2精简,降低了评估阶段的复杂度;在精简的分布式系统示意图中,运用新的文件生成树生成算法,生成执行程序的所有文件生成树,以便确定数据文件的所有传输路径;在每一个文件生成树中,运用文件传输路径生成算法,生成数据文件的所有传输路径,为确定数据文件的传输时间创造条件;在数据文件的传输路径中,运用响应时间评估算法,对数据文件的传输时间进行评估,从而确定文件生成树的状态;根据文件生成树的状态和状态变迁情况,运用Markov模型,对具有时间约束的分布式软件的可靠性进行评估。为了验证具有时间约束的分布式软件可靠性评估算法的性能,通过理论分析和软件模拟两种方式对可靠性进行评估。其中软件模拟通过可靠性评估模拟器实现,模拟器自动生成具有时间约束的分布式软件并对其可靠性进行评估。评估结果表明,上述算法具有较好的合理性、可行性和准确性。更多还原

【Abstract】 People often use the basic theories and the basic methods of the software reliability analysis at the early time when they study the reliability of distributed software. With the development of the technology of software reliability evaluation, some theories and methods about the distributed software reliability evaluation are founded. However, most of them are based on the theory of graph and evaluate the distributed software reliability by using K-terminal factoring theorem. Though these methods of evaluation are derived from theoretical analyzing and deducing, they are limited in practical applying. Because these methods only evaluate the reliability of distributed software and not reflect the effects of the other performance of distributed software on the reliability.Aiming to resolve these problems, this thesis analyze the reliability of time-constrained distributed software and deduce some computing expressions, which is based on the principle of distributed program reliability evaluation, namely combining reduction with depth-first search manner. Then based on these computing expressions, we deduce some algorithms. These algorithms include Degree-1 reduction algorithm, Series reduction algorithm, new file spanning tree algorithm, file transmission path algorithm and response time of file transmission path algorithm.Before using these algorithms, the distributed system is firstly described by applying formalized methods and we can get the sketch map of the distributed system. Then these algorithms can be applied in the sketch map. Based on the available data files on node and the degree of node, the graph of the distributed system can be reduced by using the Degree-1 reduction algorithm and the Series reduction algorithm, thus the complex degree of evaluation can be reduced. In the sketch map having been reduced, all the file spanning trees can span by using the new file spanning tree algorithm, so all the transmission paths of each data file can make sure by the file transmission path algorithm. The transmission time of each data file can be calculated by using the response time of file transmission path algorithm. By using these algorithms and Markov model, the reliability of time-constrained distributed software can be calculated out.In order to validate the performance of the reliability evaluation algorithms for time-constrained distributed software, we use two different methods. In the first methods, <WP=6>the reliability is evaluated by using the reliability evaluation algorithm. In the second example, we use the reliability evaluation simulator to evaluate the reliability. We can draw some conclusions, which including that the algorithms are rational, the process of evaluation is feasible and the result is veracious by analyzing the result of two methods.更多还原