#19586: Add is_cayley_graph
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       Reporter:  jaanos             |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-6.10
      Component:  graph theory       |   Resolution:
       Keywords:  Cayley graphs      |    Merged in:
  groups                             |    Reviewers:
        Authors:  Janoš Vidali       |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:                     |  4aaf3014fee5bb08d861636908d6733047d4a869
  u/jaanos/add_is_cayley_graph       |     Stopgaps:
   Dependencies:                     |
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Comment (by jaanos):

 Perhaps I was not being precise enough: I was talking about the generating
 set of the Cayley graph, not about the generators of the group.

 So, a user may want any of the following (where computing each relies on
 the previous):
 1. whether there exists a transitive subgroup of the automorphism group
 with the same order as the graph,
 2. one such group,
 3. a map from vertices to group elements,
 4. a (multi)set of group elements that acts as the generating set for the
 Cayley graph.

 Now, going from step 2 to steps 3 and 4 surely is not hard (4 lines of
 code), but it is not something that can be done with a simple method call,
 and step 4 it is certainly not something that can be computed from the
 group itself.

 Anyway, I was probably wrong that the map would be a better certificate
 than the group, as the former is clearly easily computable from the
 latter.

 By the way, what we're actually looking for here is a regular subgroup, so
 that's what the group method should be called (and we can also simplify
 the GAP call).

 Janoš

--
Ticket URL: <http://trac.sagemath.org/ticket/19586#comment:39>
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