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Re: Mathematica 8 bug (related to Graph[])

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119972] Re: Mathematica 8 bug (related to Graph[])
  • From: Szabolcs <szhorvat at gmail.com>
  • Date: Sat, 2 Jul 2011 05:02:31 -0400 (EDT)
  • Reply-to: comp.soft-sys.math.mathematica at googlegroups.com

On Saturday, March 19, 2011 11:19:10 AM UTC+1, Szabolcs wrote:
> 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]= 
> 
> 
> 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?
> 

A possible workaround to this is applying Uncompress@Compress to the corrupted graph before testing for isomorphism.  


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