Research On Reliability Evaluation Of Time-Constrained Distributed Software

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, 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.