#16503: q-x construction of Orthogonal Arrays
-------------------------------------+-------------------------------------
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/16503 | 71dad5d46b3fe7b343962974a75a9c199e0904a6
Dependencies: #16500 | Stopgaps:
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Comment (by ncohen):
Hello !
> 1) One lines 656-659 you have an import followed by a commented check!!
> {{{
> from sage.combinat.designs.bibd import _check_pbd
> PBD = [[relabel[xx] for xx in B if not xx in points_to_delete] for B in
TD]
>
> # _check_pbd(PBD,n,[q,q-x-1,q-x+1,x+2])
> }}}
> why is that?
It is something I used while implementing the construction and as it said
something about the PBD I left it. I updated that comment as that troubled
you.
> 2) This is wrong (lines 730-731)
> {{{
> # The next is always True, because q is a prime power
> # orthogonal_array(k+1,q,existence=True) and
> }}}
The line before that one is
{{{
orthogonal_array(k+1,q-x+1,existence=True) and
}}}
> 3) I bounced into something bad: I wanted to change in
`find_recursive_construction` the
> {{{
> assert k >= 3
> }}}
> into a
> {{{
> assert k > 3, "you do not need recursion for k<4"
> }}}
> since it is trivial to build one latin square. But it appears that the
recursive constructions is called with k=3 many times! so bad! This has to
be corrected... but hopefully, not here. I guess that #16535 would be the
good place.
Why in #16535 ? What we need to do is add a case for k=3 in the
`orthogonal_array` constructor.
I fixed the things above, plus an apparently incorrect `1<x`.
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/16503#comment:7>
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