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Wrong output SubdigraphsMonomorphisms #704

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MeikeWeiss opened this issue Sep 18, 2024 · 3 comments
Open

Wrong output SubdigraphsMonomorphisms #704

MeikeWeiss opened this issue Sep 18, 2024 · 3 comments
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bug A label for issues that are bugs resolved-pending-release A label for issues that have been resolved and that can be closed when a new version is released.

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@MeikeWeiss
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MeikeWeiss commented Sep 18, 2024

I have the graph

 d:=Digraph([ [ 2, 3, 4, 5 ], [ 1, 3, 4 ], [ 1, 2, 4, 5 ], [ 1, 2, 3, 5 ], [ 1, 3, 4 ] ]);

and I would like to compute all subgraphs isomorphic to K_{2,3} with SubdigraphsMonomorphisms.
In my opinion the output here is wrong because the subgraph/transformation defined by Transformation( [ 2, 5, 1, 3, 4 ] ) which is contained in the output of MonomorphismsDigraphsRepresentatives(CompleteMultipartiteDigraph([2,3]),d) is missing. This subgraph has a different edge set than the subgraphs defined by the returned transformations of SubdigraphsMonomorphisms(CompleteMultipartiteDigraph([2,3]),d).

gap> SubdigraphsMonomorphisms(CompleteMultipartiteDigraph([2,3]),d);
[ Transformation( [ 1, 3, 2 ] ), Transformation( [ 1, 4, 2, 3 ] ), Transformation( [ 3, 4, 2, 1 ] ) ]
gap> MonomorphismsDigraphsRepresentatives(CompleteMultipartiteDigraph([2,3]),d);
[ Transformation( [ 1, 3, 2 ] ), Transformation( [ 1, 3, 2, 5, 4 ] ), Transformation( [ 1, 4, 3, 2 ] ), Transformation( [ 2, 5, 1, 3, 4 ] ) ]
@james-d-mitchell james-d-mitchell added the bug A label for issues that are bugs label Sep 18, 2024
@MeikeWeiss
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@james-d-mitchell Do you have any idea how to solve it?

@james-d-mitchell
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Sorry @MeikeWeiss didnt have time to investigate yet, I'll try to look this afternoon

@james-d-mitchell
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@MeikeWeiss I spent some time yesterday trying to figure out what's going on here, I can confirm that I can reproduce the bug. I'm not yet sure what is causing it, I'll investigate further today and hopefully find a fix.

james-d-mitchell added a commit to james-d-mitchell/Digraphs that referenced this issue Oct 10, 2024
james-d-mitchell added a commit that referenced this issue Nov 11, 2024
@james-d-mitchell james-d-mitchell added the resolved-pending-release A label for issues that have been resolved and that can be closed when a new version is released. label Nov 12, 2024
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