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MathGroup Archive 2003

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Problems With Combinatorica -> Graphs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44179] Problems With Combinatorica -> Graphs
  • From: "Thiery Balser" <thiery.balser at gmx.net>
  • Date: Sat, 25 Oct 2003 06:26:30 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Everybody!


I'm kind of confused: I'm just playing a bit with Mathematica's (4.1 on
Windows) Combinatorica package.

What I've tried:

(*--- Begin Mathematica Code -- *)
g1={
    {1,3,4},
    {1,4,3},
    {1,2},
    {1,2}
    }
g1g=FromAdjacencyLists[g1];

(* and *)
g2={
      {2,4,3},
      {1,3},
      {2,4,1},
      {3,1}
};

g2g=FromAdjacencyLists[g2];

(*--- End Mathematica Code -- *)

Then I wanted to see how the function Isomorphism works.
Well, first I tested IsomorphicQ[g1g,g2g] and got false which really
astonishes me. There _is_ an isomorphism between Graph1 and Graph2,
namely, let g be this isomorphism, then
g(1)=1, g(2)=3,g(3)=2 and g(4)=4 satisfies the requirements.

Why does Mathematica not recognize those two graphs as isomorphic?

What exactly does isomorphism return? It seems that there's no proper
documentation.


Thanks in advance for any kind of help,


Thiery



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