[Nauty] canonical label for directed graphs
bdm at cs.anu.edu.au
Wed Aug 3 22:38:27 EST 2005
* Gordon Royle <gordon at csse.uwa.edu.au> [050803 22:24]:
> nauty already computes canonical labellings for directed graphs....
> there is no need to modify the algorithm.
> However the default settings for the "options" structure is to have
> options.digraph set to FALSE - presumably because some speed can be
> gained if the algorithm can rely on the input being undirected
> without actually confirming that edge j-i is present when it notices
> edge i-j.
> So, just set options.digraph = TRUE before your call to nauty, and it
> will treat it as a directed graph
If you are calling nauty from your own problem, I also recommend
options.mininvarlevel = 1;
options.maxinvarlevel = 99; /* or something */
options.invarproc = adjacencies;
For long jobs you might want to test whether this helps or hurts.
The values of these parameters can change the canonical labelling
so be consistent.
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