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Mathematica 8 bug (related to Graph[])

  • To: mathgroup at smc.vnet.net
  • Subject: [mg117457] Mathematica 8 bug (related to Graph[])
  • From: Szabolcs <szhorvat at gmail.com>
  • Date: Sat, 19 Mar 2011 05:18:59 -0500 (EST)

Dear MathGroup members,

There appears to be another bug in graph processing functions:

In[1]:= jj = Subgraph[Graph[{1, 2, 3, 4}, {3 -> 4}], {1, 2, 3}]

Out[1]= <picture of a graph>

In[2]:= IsomorphicGraphQ[jj, Graph[{1, 2, 3}, {}]]

Out[2]= False

In[3]:= InputForm[jj]

Out[3]//InputForm=
Graph[{1, 2, 3}, {}]

Strangely, if I copy and paste the output from Out[1] into the
IsomorphicGraphQ[] function, then the problem doesn't manifest
itself!  To reproduce it, evaluate the input exactly as shown above
(try in a new session).  Generally, any action that pulls the graph-
expression through the front-end seems to "fix" the problem.

Can you reproduce the bug in Mathematica 8.0.1?

Cheers,
Szabolcs


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