Ensuring Time Resolution Compatibility for Simulation Executives, Job Scheduling, and Data Exchange

Time, as a concept, is something everyone experiences. It seems like a simple concept used to measure the temporal progress of our lives, associated events, and accomplishments. Time is also often a key independent variable in the mathematical formulation of physics-based models of dynamical systems; this is particularly true of space systems modeling and simulation. As a result, many simulation systems use time as the basis for their simulation executives. While a simple concept for most daily activities, time representation quickly becomes more complex and nuanced when used as the independent variable in numerical simulations. This paper explores some key factors for time representations in time-based simulations. It discusses the principal time lines that must be defined and the relationships between those time lines. It analyzes the core time representation within the simulation executive and the relationship between an underlying discrete time ticks of the executive and mapping into a continuous floating point representation of time. This leads to a discussion of model job scheduling and the relationship to the native executive time representation. From this, job scheduling relationships and constraints will be derived based on the executive time representation. Finally, this will lead to a discussion of data exchange rates and constraints for time synchronized distributed simulations. The paper concludes with observation and recommendations on managing time resolution compatibility across time synchronized distributed simulations.