Software Engineering and Formal Methods by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783319929705
Publisher: Springer International Publishing

A good example of an application implementation in this system is SPF-WCA. The client requests for an analysis to be performed by sending the system under test and all required files in an archive to the Dispatcher REST endpoint. For this particular problem, we partition the decision tree of the application. That is, for every branching instruction encountered, we consider both the true and false options. This creates a binary tree with every node representing a branch in the system under test. At this point, the Dispatcher interrogates the Bridge regarding how many nodes are available for use, and partitions the entire system decision tree into subtrees to be analyzed separately.

One of the problems we encountered is that the analysis time of a given subtree is wildly unpredictable, and this unpredictability can cause an unequal work distribution. As we are using static partitioning, we have developed a statistical approach to the problem, depicted in Fig. 3 for partitioning a binary decision tree. Because the cost of analyzing each subtree is essentially random, we over-partition the problem space and assign multiple subtrees to the individual workers. As the number of problems approaches infinity, the level of work distribution approaches equality. Once the tasks are defined, the Dispatcher assigns a block of tasks to a Daemon and sends the task requests to a Bridge which forwards the tasks to the defined Daemon. The Daemon adds the tasks to an internal queue and instantiates Worker instances as resources become available. The Workers perform the tasks and continually report progress back through the Daemon, the Bridge, and to the Dispatcher. The Dispatcher is then able to integrate those results into a single worst-case analysis, which is made available to the client through the same REST endpoint. As the results in Sect. 4 indicate, this static over-partitioning is effective in practice.

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