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Wrong output SubdigraphsMonomorphisms #704

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MeikeWeiss opened this issue Sep 18, 2024 · 0 comments
Open

Wrong output SubdigraphsMonomorphisms #704

MeikeWeiss opened this issue Sep 18, 2024 · 0 comments
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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
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