Causality and Proactive Cancellation

Optimistic time warp simulators should stop the rapid propagation of incorrect events to avoid reaching a catastrophic state (a state where out of order event execution is always a step ahead of its corrective measures). A distributed cancellation mechanism using total clocks was proposed earlier to avoid such catastrophic states. In this paper, we present a proactive cancellation mechanism using a vector of event counter range to address the scalability issues with the previously defined solution. As opposed to total clocks, this timestamp mechanism (a.k.a. plausible total clocks) consists of constant size vectors and are independent of the number of simulation objects in the simulation. The events generated due to an out of order execution are pro-actively canceled by determining its causality relation with the already annihilated events. We present a proof of correctness of the distributed cancellation mechanism and also show that catastrophic states are avoided with this proactive cancellation mechanism. This cancellation mechanism assumes FIFO communication layer, static inter-connection topology, and logical processes consisting of several simulation objects