On Monday, January 30, 2017 at 9:48:22 AM UTC-5, Thierry
(sage-googlesucks@xxx) wrote:
>
> Hi,
>
> On Mon, Jan 30, 2017 at 03:44:06AM -0800, jamel Dammak wrote:
> > Dear sir,
> >
> > there is an error concerning the function "is_prime" for graphs in
> > Sagemath, section Graph Theory.
> >
> > Here is a conter-example.
> >
> > g1=Graph({0:[1,4],1:[0,2,4],2: [1,3,4],3:[2],4:[0,1,2]});g2=G
> > raph({0:[1],1:[0,2,4],2:[1,3,4 ],3:[2,4],4:[1,2,3]})
> > #g1.show();g2.show();
> > #[1,4] is a module of g1 so g1 is not prime
> > #[2,4] is a module of g2 so g2 is not prime
> > g2.is_isomorphic(g1), g1.is_prime(),g2.is_prime()
> >
> > This is a conter-example with two isomorphic graphs g1 and g2 on 5
> > vertices giving two different results
> > with the function "is prime".
> >
> > I have an algorithm giving the list of all prime graphs on at most 8
> > vertices.
>
>
> Great, go ahead, ask for a trac account, and propose your changes.
>
I've reported this at https://trac.sagemath.org/ticket/22281
Note it depends on an optional package, so this may be part of the issue.
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