#16391: Helper functions for OA constructions
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       Reporter:  ncohen             |        Owner:
           Type:  enhancement        |       Status:  needs_info
       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     |  90f828fb2904fc5083baa8b45af97d6dc7740f54
   Dependencies:  #16370             |     Stopgaps:
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Changes (by vdelecroix):

 * status:  needs_review => needs_info


Comment:

 Hi,

 1) What you called OA with holes are "incomplete orthogonal array" in the
 Handbook (as well as their sisters "incomplete transversal design" and
 "incomplete set of MOLS"). See p 193-194. And the one you are interested
 in, the "OA(k,n) - x.OA(k,1)", are also denoted "OA(k,n; 1, ..., 1)". Am I
 right? If this is true, I would rather write a function
 `incomplete_orthogonal_array(k,n,holes)` where holes is a tuple of
 integers to fit with the standard names and notations. I also saw some
 general results in the Handbook (Theorems 4.16 and 4.17) about one hole
 and k=4,5... and a beautiful table of IMOLS.

 2) From the function you wrote, it is very easy to
 - allow `x` as None, in which case the function tries to optimize the
 number of holes
 - have an optional argument `OA` such that, if it is provided, the
 function looks for holes inside this orthogonal array.

 I did the change myself but the function looks a bit uglier so I am not
 sure what to do. I would like to have those two functions to study the
 number of holes depending on the OA. But on the other hand, I tried with
 the OA(10,4) that we have but it took lifetime to obtain the answer 9.

 A perhaps cleaner way to do things is to have two functions that would
 looks like
 - `incomplete_orthogonal_array(k,n,holes)` (this function would be
 available from the global namespace)
 - `look_for_holes_in_my_OA(OA,k,n,holes)`

 What do you think?

 Vincent

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Ticket URL: <http://trac.sagemath.org/ticket/16391#comment:13>
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