ANALYZING CONCURRENT AND FAULT-TOLERANT SOFTWARE USING STOCHASTIC REWARD NETS

We present two software applications and develop models for them. The first application considers a producer-consumer tasking system with an intermediate buffer task and studies how the performance is affected by different selection policies when multiple tasks are ready to synchronize. The second application studies the reliability of a fault-tolerant software system using the recovery block scheme. The model is incrementally augmented by considering clustered failures or the effective arrival rate of inputs to the system. We use stochastic reward nets, a variant of stochastic Pertri nets, to model the two software applications. In both models, each quantity to be computed is defined in terms of either the expected value of a reward rate in steady-state or at a given time θ, or as the expected value of the accumulated reward until absorption or until a given time θ. This allows extreme flexibility while maintaining a rigorous formalization of these quantities. © 1992.