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. Best regards. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.