correction to energy term in dirgen
The energy term assumed in the cost function for dirgen and other associated commands (e.g. dirstats, dirsplit, dirmerge, …) was incorrect, assuming a 1/r² relationship, when this should be 1/r (corresponding to a 1/r² repulsion force). Thanks to @Kerstin for reporting this.
This has now been rectified, and will change the directions generated by dirgen slightly, and also affect the energy values reported by dirstats. Thankfully, it seems the differences are minor, and not necessarily anything to worry about (see full discussion on GitHub for details).
In addition, dirgen has been modified to perform multiple random restarts (10 by default) to ensure a more globally optimal solution is found.