#16395: adjacency_matrix raises error for large multigraphs
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       Reporter:  lipshitz           |        Owner:
           Type:  defect             |       Status:  needs_info
       Priority:  minor              |    Milestone:  sage-6.3
      Component:  graph theory       |   Resolution:
       Keywords:                     |    Merged in:
        Authors:                     |    Reviewers:
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/lipshitz/ticket/16395            |  ec8ebced3d73d124c10fabfd648b5033693f4382
   Dependencies:                     |     Stopgaps:
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Comment (by ncohen):

 Hello !

 > Fair enough!  On the other hand, the relevant notion here seems to be
 the density of the honest graph obtained by replacing each multiple edge
 with a single edge.

 I agree, but this is too expensive. And this is equivalent to building a
 sparse matrix, computing the number of non-null entries, and converting it
 to a dense matrix if it saves space.

 > I could change the code to compute that, and decide whether to return a
 dense or sparse matrix based on that computation. Or just have multi
 graphs always return a dense matrix, like the code does now. Do you have a
 preference?

 Returning a dense matrix in all cases makes sense to me.

 Nathann

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Ticket URL: <http://trac.sagemath.org/ticket/16395#comment:9>
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