results directory

[deitrr]

Another directory that needs to be manually created by the user before the code can be run. It would be better for the code to search for this directory and create it if necessary.

[nabajour]

code should check for that directory and create it if needed. And also check for existence of files in there. We need a policy in case there are files (abort, overwrite, resume).
And the output directory could have a default and be overridden by command line option.

We could even restart simulation from an existing directory, I think it should contain everything needed to run the simulation, reading the initial conditions from the h5 files.