[Nauty] equitable partitions..

[Brendan McKay]

* Gordon Royle <gordon at csse.uwa.edu.au> [050406 18:14]:
> Suppose I have a partition of the vertices of a graph, and wish to 
> determine whether or not it is equitable...
> 
> Is it possible to determine this by making a call to a routine within 
> nauty (even if I am not interested in finding groups etc).
 
There is a test function 

  boolean equitable(graph *g, int *lab, int *ptn, int level, int m, int n)

in the file nautaux.c that is in the nauty package but not used for
anything else in the package.

The partition is given by (lab,ptn) in the usual fashion.  If you
are going to use 0 to mark the cell endings in ptn[], set level=0.
In general, the cells end with those positions i such that
ptn[i] <= level.

Brendan.