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Re: Mathematica 8 bug (related to Graph[])
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Szabolcs
Jul 2, 2011, 5:06:17 AM7/2/11
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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?
>
> 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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