I'm new to molecular dynamics (MD) simulations. What is the complexity of a molecular dynamics simulation in terms of simulation time? In other words, if I want increase the simulated time from 10 nanoseconds to 20 nanoseconds, what can I expect in terms of the increase in runtime?
Complexity of MD simulations
molecular dynamics;complexity
Molecular dynamics simulations are linear (O(n)) in the length of time simulated (assuming that the single timesteps ($\Delta t$) are unchanged).  Since each timestep is dependent only on the previous configuration (and not any of those prior to that), increasing the number of timesteps results in a linear increase in time.