#16391: Helper functions for OA constructions
-------------------------------------+-------------------------------------
       Reporter:  ncohen             |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-6.3
      Component:  combinatorial      |   Resolution:
  designs                            |    Merged in:
       Keywords:                     |    Reviewers:
        Authors:  Nathann Cohen      |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:  u/ncohen/16391     |  41a9a247df5925a7067421a03093b0bc01155671
   Dependencies:  #16370             |     Stopgaps:
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Comment (by ncohen):

 Yo !

 > I do not agree with your corrections. By definition, the holes are
 subsets of the ground set `V = {0,...,n-1}`. Perhaps it depend on where we
 read the definition.

 Well, I did not find definition of incomplete OA in the handbook though
 they define incomplete transversal designs, and for this they introduce
 sets `H_1,H_2, ...`. Well, to define a hole in general you need to give a
 subset for each column... Your phrasing assumes that the OA has been
 relabelled so that the coordinates of the hole are the same in every
 column... But honestly everybody would understand it the way it is, adding
 this `^k` just emphasizes that we give the coordinate for every column.

 > Could we just get rid of the caching and return list of lists in the
 very same way as `orthogonal_array`?

 Don't you want to review #16353 ? This would make everything MUCH easier.

 I am willing to implement this correctly and -- if posible -- uniformly,
 but if people refuse to review stuff like #16353 for theological reasons
 then I am stuck, and I have no other way but to find workarounds.

 In the constructions I will add when all this will be reviewed this
 function is called often. You can see that it will be called by the new
 version of Wilson's theorem, because holes are realy needed there. And it
 will be good to have it cached.

 > The time needed to find 3 disjoint blocks is not big compared to the
 time you need to build an orthogonal array. It would make more sense to
 implement the caching at the level of `orthogonal_array`. And I think, it
 would better if done in another ticket.

 Come on man. All the boolean answers should be cached. It costs nothing,
 and it can only help.

 Nathann

--
Ticket URL: <http://trac.sagemath.org/ticket/16391#comment:35>
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