一個分析時間限制之分散式程式可靠度的傳輸時間評估模型

Abstract

即時性分散式計算系統現在已被廣泛的應用在軍事,醫藥,工業及其他許多 領域.在設計即時性分散式計算系統時, 可靠度的預先評估是一項重要的 考量.如果在設計時缺乏準確合理的可靠度評估指標,將可能導致其設計出 之結果無法達到預期之標準.於是[Sheng92]提出一個檔案傳輸時間的評估 模型,並以此模型為根據,提出了時間限制的分散式程式可靠度(TCDPR)做 為即時性分散式系統的可靠度分析指標.然而在他所提出的檔案傳輸時間 的評估模型中仍有不甚完整值得討論之處.這一篇論文提出另一種檔案傳 輸時間的評估模型.此模型中在傳送檔案之前,我們都先計算出較有效之路 徑,以減少檔案傳送之時間,如此可增加此程式執行能在其時間限制前完成 之機率.經此修改後,平均而言,我們將可以得到較高的可靠度,而此種結果 對時間限制的分散式系統而言更加合理在計算時間限制的分散式程式可靠 度的評估方面,在論文中也分析了數種化簡法 ,並提出一個時間檢查的化 簡法,以加速計算可靠度的過程. Distributed real-time systems have been widely applied in various application domains, including the military, industrial manufacturing, and medical care sectors. Reliability analysis is an important issue in designing distributed real-time systems for various applications. The lack of an appropriate reliability to guide designers during the design of a system may result in problems such as difficulty in meeting design goals, high cost for modifying the system, and sometimes unexpected catastrophes while the system is in operation. For this reason, [Sheng 92] proposed a file transmission time evaluation model. Based on this model, he proposed time- constrained distributed program reliability (TCDPR) as a reliability index for real-time distributed computing systems to analyze the probability of the successful execution of a time-constrained program. However, there are some points of the model not so considered and worth discussing. In this thesis, we propose a new file transmission time evaluation model modified from the model proposed by [Sheng 92]. In this model, we find appropriate and efficient transmission paths to transmit the needed data files to the node that contains the processing program. In the proposed model, the time required to transmit files is reduced, so there is a greater probability that the program will finish processing before the time constraint is reached. In other words, the proposed modification yields greater reliability, it is more reasonable for a real-time distributed computing systems. In computing the TCDPR, this thesis also analyzes the evaluation process and several previous reliability preserving-reductions and proposes a time_check deletion to reduce the computing tree and speed up the evaluation process.