handling of big initial condition files
Once the Python wrapper needs to generate initial conditions (either fields, or particles) bigger than a few gigabytes we're in trouble. In particular, we need to make use of parallel file systems (which the Python wrapper cannot currently do). We need to decide on how to handle this in the future.
Initial suggestion: write a distinct C++ code that can do various complicated initial condition tasks, and run it as a separate job beforehand. If the DNS is big enough to require this, it means the additional effort of keeping track of which initial condition job has finished yet is worth it.