The temporary array to re-order elements and output them sequentially costs too
much memory on the entire graph. Using RandomAccessFile is slower but enables
Setup to run on any VM.
*THIS IS WIP*
I still need to measure *how much* slower this method is. On RIOC previous
version with the temporary array used 2TB of RAM (!) and around 20h to compute.
Right now tests are running on monster (but IO is really not great...), because
all others VM are already in use.