ABSTRACT We present an optimal solution to the problem of allocating communicating periodic tasks to heterogeneous processing nodes (PNs) in a distributed real-time system. The solution is optimal in the sense of minimizing the maximum normalized task response time, called the system hazard, subject to the precedence constraints resulting from intercommunication among the tasks to be allocated. Minimization of the system hazard ensures that the solution algorithm will allocate tasks so as to meet all task deadlines under an optimal schedule, whenever such an allocation exists. The task system is modeled with a task graph (TG), in which computation and communication modules, communication delays, and intertask precedence constraints are clearly described. Tasks described by this TG are assigned to PNs by using a branch-and-bound (B&B) search algorithm. The algorithm traverses a search tree whose leaves correspond to potential solutions to the task allocation problem. We use a bounding method that prunes, in polynomial time, non-leaf vertices that cannot lead to an optimal solution, while ensuring that the search path leading to an optimal solution will never be pruned. For each generated leaf vertex we compute the exact cost using the algorithm developed in [1]. The lowest-cost leaf vertex (one with the least system hazard) represents an optimal task allocation. Computational experiences and examples are provided to demonstrate the concept, utility, and power of the proposed approach.

QOS ADAPTATION IN REAL-TIME SYSTEMS by Tarek F. Abdelzaher Chair: Kang G. Shin We propose to design, implement, and evaluate a software framework, called the Adaptware, that consists of architectural support, resource-management mechanisms, and programming abstractions for adapting Quality-of-Service (QoS) to dynamically-fluctuating resource capacity and demands. This framework is to reduce the cost and time of real-time software development by providing the infrastructure necessary for building reusable multi-purpose real-time software components. In much the same way as today's consumers can buy software and hardware components from different vendors and construct a computing environment tailored to their needs, the proposed framework will provide the means of building and integrating real-time system components so as to preserve their temporal correctness while making it possible to dynamically compute predictable end-to-end temporal guarantees commensurate with available resour...

Aristotelian, or non-Platonist, realism holds that mathematics is a science of the real world, just as much as biology or sociology are. Where biology studies living things and sociology studies human social relations, mathematics studies the quantitative or structural aspects of things, such as ratios, or patterns, or complexity,

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