[Nauty] directg

[Brendan McKay]

* Sterten at aol.com <Sterten at aol.com> [040802 23:34]:
> with directg, IMO it would be useful to be able to specify a range  for
> indegree and outdegree.

Good idea.
  
> why can't I output any graphs from countg ?
> e.g.: geng 7 -bf | countg -g0 | directg -T     won't  work

countg only counts graphs.  To select graphs use pickg.
  
>  how to count all directed forests ?

No efficient way is provided.  You can get your idea to work:
   geng 7 -bf 0:6 | pickg -g0 | directg -To
but it isn't very fast.

>  how to count all directed acyclic graphs ?

There is no easy way provided.  One day.  You can fetch the
digraphs themselves up to order 8 here: 
   http://cs.anu.edu.au/~bdm/data/digraphs.html

Brendan.