Restarts

The FFEA runner has the possibility to continue or extend a simulation that was completed or even crashed. In the case of calc_noise being enabled we take care that random number generator we use, RngStreams, recovers the state of the last time step calculated, ensuring that unwanted correlations arise.

When a simulation is to be continued, one will need:

a trajectory, to get the positions of the nodes and, depending on the configuration, their velocities and forces. The new snapshots will be appended after the last one found.
a checkpoint file, that will indicate the state of the random number generators, to ensure that correlations and consequent artifacts never arise accidentally.
a measurement file, that will be extended with the new measurements.

The previous run will have provided this set of files, their names being specified in the FFEA input file through keywords:

trajectory_out_fname
checkpoint_out , with default name <ffea-input-file>.fcp
measurement_out_fname
det_measurement_out_fname, with default name <ffea-measurement-file>.fdm, only if:
- ffea was not run with the -d flag or
- your system has more that one blob.

In addition one needs to modify the already used FFEA input file, to indicate that the will to extend to simulations. Specifically one needs to set:

< restart = 1 >
< checkpoint_in = <valid-checkpoint-file> > while keeping trajectory_out_fname and measurement_out_fname unchanged.

There is a last rule that applies. Values for files checkpoint_out and checkpoint_in must differ. Therefore, if in the previous run checkpoint_out was not specified we recommend to rename the old checkpoint_out file with its default name to something else and then use it as checkpoint_in.

Backups

Output files will never be overwritten by the FFEA runner, but will be renamed instead. This way, if a new simulation were launched by error in the same folder where a previous simulation was run, every one of the following files:

checkpoint_out
trajectory_out_fname
measurement_out_fname
det_measurement_out_fname

will be renamed to __<old-file-name>__bckp.<N>, where N is the smallest natural number found so that the resulting text does not match the name of any existing file in the working folder.