[Nauty] Canonicalizing directed graphs.

[Alexander Engström]

On Mon, 1 Mar 2004, Brendan McKay wrote:

...

> Incidentally, acyclic directed graphs don't much like the
> default parameters of nauty.  For better average efficiency,
> use the invariant "adjacencies".
>
> In dreadnaut:   k=1 10 *=13
>
> In C:
>     options.invarproc = adjacencies;
>     options.mininvarlevel = 1;
>     options.maxinvarlevel = 10;
>   (and include nautinv.c in the program).
>
> The value "10" is arbitrary, you could try adjusting it for best
> behaviour in your application.  However note that the canonical
> labelling may depend on the value.

The performance improved quite much. One of the graphs, with 49
vertices and 238 edges, was not possible to handle with nauty before.
After working with it a day on a machine which uses 20 seconds for
"geng -u 10", i quited nauty.

With the new parameters, the time used was under a second. So thanks
for the advice,

Alexander