#18784: Tutte connectors for matroids
-------------------------------------+-------------------------------------
       Reporter:  Rudi               |        Owner:  Rudi
           Type:  enhancement        |       Status:  positive_review
       Priority:  major              |    Milestone:  sage-6.8
      Component:  matroid theory     |   Resolution:
       Keywords:                     |    Merged in:
        Authors:  Rudi Pendavingh    |    Reviewers:  Chao Xu
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/Rudi/tutte_connectors_for_matroids|  
9d932ee9b5e693b46fd7bfbd0da2ebb1d1bfdcc2
   Dependencies:                     |     Stopgaps:
-------------------------------------+-------------------------------------
Changes (by chaoxu):

 * status:  needs_review => positive_review
 * reviewer:   => Chao Xu


Comment:

 Hi Rudi,

 Positive review.

 Here are more things I have tried:

 Some 4-connected(and not 5-connected) binary matroids given by Gordon
 Royle.

 each list is a matroid and each number in the list expressed in binary is
 a column of a matrix representing the matroid.

 {{{
 [[1,2,4,7,8,11,13,14,16,21,25,31],
 [1,2,4,8,15,16,21,25,32,41,51,63],
 [1,2,4,8,15,16,21,22,32,41,42,51],
 [1,2,4,7,8,13,16,31,32,35,52,61],
 [1,2,4,8,15,16,32,54,64,90,109,113],
 [1,2,4,7,8,11,13,14,16,19,21,22,25,31],
 [1,2,4,8,15,16,21,25,30,32,37,41,44,51],
 [1,2,4,8,15,16,21,25,30,32,37,41,46,51],
 [1,2,4,8,15,16,21,25,30,32,37,41,51,52],
 [1,2,4,8,15,16,21,25,30,32,37,41,51,54],
 [1,2,4,8,15,16,21,27,28,32,39,41,51,56],
 [1,2,4,8,15,16,21,22,27,28,32,41,42,51],
 [1,2,4,8,15,16,21,22,27,32,39,41,42,51],
 [1,2,4,8,15,16,21,22,27,32,41,42,44,51],
 [1,2,4,8,15,16,21,22,32,41,42,51,61,62],
 [1,2,4,7,8,11,13,14,16,19,21,22,25,26,28,31],
 [1,2,4,8,15,16,21,25,30,32,37,41,46,51,52,56],
 [1,2,4,8,15,16,21,25,30,32,37,41,46,51,54,56],
 [1,2,4,8,15,16,21,25,30,32,37,41,46,51,54,58],
 [1,2,4,8,15,16,21,27,28,32,39,41,44,51,52,56],
 [1,2,4,8,15,16,21,22,27,28,32,39,41,42,51,52],
 [1,2,4,8,15,16,21,22,27,28,32,39,41,42,44,51],
 [1,2,4,8,15,16,21,22,27,32,39,41,42,51,61,62],
 [1,2,4,7,8,11,13,14,16,19,22,31,32,35,52,61],
 [1,2,4,7,8,11,13,14,16,19,28,31,32,35,52,61]]
 }}}

 Applying `is_kconnected(4)` and `is_kconnecte(5)` returns desired results.

--
Ticket URL: <http://trac.sagemath.org/ticket/18784#comment:25>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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