# [Nauty-list] graph isomorphism

Sara Voss sarasvoss at gmail.com
Wed Feb 18 11:55:19 EST 2009

```Thank you for the help and the quick response.

On Tue, Feb 17, 2009 at 1:05 AM, Brendan McKay <bdm at cs.anu.edu.au> wrote:
> There isn't such a procedure.  You just need to compare them
> word by word.  Here are two methods:
>
> boolean
> aresame_packed(graph *g1, graph *g2, int m, int n)
> {
>    set *g1p,*g2p,*g1pmax;
>
>    g1pmax = g1 + m*(size_t)n;
>    for (g1p = g1, g2p = g2; g1p < g1pmax; ++g1p, ++g2p)
>        if (*g1p != *g2p) return FALSE;
>
>    return TRUE;
> }
>
> #define ARESAME_PACKED(g3,g2,m,n) memcmp(g1,g2,(m)*sizeof(graph)*(n))
>
> In each case I am assuming the same value of m is used for each graph.
> I'm also ignoring vertex colours: you must have the same number of
> vertices of each colour (which is best tested before calling nauty
> and not after).
>
> Brendan.
>
> * Sara Voss <sarasvoss at gmail.com> [090217 17:53]:
>> I read through the manual and don't think I found the answer to my
>> question.  I am trying to use nauty to check for isomorphisms using a
>> dynamic packed form.  Is there a built in aresame function for the packed
>> form or just the sparse form.  Thanks.
>
>> _______________________________________________
>> Nauty-list mailing list
>> Nauty-list at cs.anu.edu.au
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>
>

--
Sara Voss

```

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