Checks whether there are checkpointed data files in a specific format given a simulation number.
Details
This function checks whether checkpointed data files are available for loading.
Checkpointed data files are incrementally saved during the simulation and
loaded when a simulation job has been cancelled and restarted. This is done
automatically within the netsim_hpc function.
Checkpointed data files are searched for in a specific subdirectory relative
to the current working directory: data/sim<x>, where <x> is the
simno value. Within that directory check_cp looks for files
ending .cp.rda, which is the standard checkpoint data file name. Note
that these standards for file directory and name are consistent with the
save_cpdata module function. If running simulations using the
netsim_hpc function, this data saving module will automatically
be inserted in the workflow of a simulation.
The files are tested to see that they are of similar size, meaning that no
file is less than 50% of the average file size of the others. Smaller size
files usually indicates that the interim file saving was interrupted. If the
files exist and are of correct size, a full directory name is returned, else
NULL is returned.