Specifying initial conditions for particles from a file / output of previous run

[matt-graham]

Is it possible to set the initial particle states (positions and velocities) via a file similar to how the initial conditions of variables (fields) in Nektar++ can be set from a file? More generally, is it possible to checkpoint the complete state of a simulation and then restart another simulation from that state? The checkpoint .chk files outputted by Nektar++ and particle states recorded in the particle_trajectories HDF5 file seem to record the required information, but I can't see an obvious way of setting the particle states from a file.

From a benchmarking perspective it would be useful to be able to start simulations from a more reflective / equilibrated initial state after any initial transient behaviour has died down, and similarly most approaches for performing calibration / data assimilation with the simulations require being able to start the simulation from a previously recorded state.