#16323: Construction of BIBD with k=5
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Reporter: ncohen | Owner:
Type: enhancement | Status: positive_review
Priority: major | Milestone: sage-6.3
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers: Vincent Delecroix
Authors: Nathann Cohen | Work issues:
Report Upstream: N/A | Commit:
Branch: | 8eac6d069e162aed9d4fc1ae3f654d0b446573da
u/vdelecroix/16323 | Stopgaps:
Dependencies: #16279 |
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Comment (by ncohen):
Yo !!
Thanks for the review !
> I bet that there are some PBD constructions in the Handbook... We should
keep in mind to reuse this code at some point.
Indeed, but my fear with PBD construction is that it may become harder to
detect if we can build one. I mean.. If you have a `(100,[4,6,8])-PBD` and
a `(6,[3])-PBD` then you have also a `(100,[3,4,8])-PBD`, stuff like that.
You can really mix a lot of different things there, soooo... Well. It may
be tricky. We will do it, but it will be tricky to do it well.
> I do not care too much. But, when I opened the file the first time it
was difficult to found the logic.
AHahah. ALl this is there for "historical reasons" I fear. Implemented one
after the other. I expect that it will be cleaned several times in the
future.
> Indeed, this was my main question. (I had a look at various paper about
difference families, and there are a lot about k=3,4,5, very few about k=6
and almost none about k>=7; excepted existence result for very large v).
Indeed, but Julian R. Abel told me that some recursive construction may be
by itself sufficient to generate all (v,6,1)-BIBD with v>1000. Looks like
when you have a lot of recursive construction you can do almost
everything, and that some base cases will be the only missing things
afterwards.
Ahahaah.
The point is that it is all a lot of work, and all an interesting work
too. And I would like to add it someday, but for the moment I would like
to finish implementing all the OA/TD/MOLS related code. I have some new
constructions to add but I did not write the branch yet for it would
depend on other tickets, and I am pretty sure that the main functions I
need will be rewritten and changed during the reviews, so I don't dare
write this yet as it will mean a lot of rebase. But when the OA/TD/MOLS
stuff will be done, both PBD and BIBD with larger blocks will be on the
table.
> I found the work done in the branch is enough for the ticket so I set to
positive review.
Thaaaaaaaaaaaaaanks ! I will write to the author of the pdf file tomorrow
`:-)`
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/16323#comment:20>
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