Module replication for fault-tolerant real-time distributed systems

The problem of replicating and scheduling periodic tasks in a multiprocessor system, under timing and dependency constraints, is presented. The objective is to maximize the probability of successful completion of all tasks in the system. A precedence graph that is general, with chain, AND, OR, and loop subgraphs is assumed. To achieve high probability of successful completion of tasks in the system, several modules are chosen for replication and executed, regardless of whether a failure actually occurs or not. The replicated modules are chosen in an optimal way, and are added to the set of the executable tasks only if that increases the probability of the completion. The failure model of the modules in the system is general and realistic.