#16884: A database entry for Quasi-difference matrices
-----------------------------------------+----------------------------
Reporter: ncohen | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: combinatorial designs | Resolution:
Keywords: | Merged in:
Authors: Nathann Cohen | Reviewers:
Report Upstream: N/A | Work issues:
Branch: public/16884 | Commit:
Dependencies: #16879 | Stopgaps:
-----------------------------------------+----------------------------
Comment (by ncohen):
Oh, I forgot to say why this patch is useful:
There is a problem currently with the way Sage manages Vmt vectors.
Indeed, from a Vmt ont can build a quasi-difference matrix with `k=m+2`
columns, and for `OA(9,514)` (see last commit) the OA construction has to
do a small change: 1) build the QDM from the Vmt; 2) Remove a column from
the QDM; 3) Build the OA from the reduced QDM.
Now, building the OA from the reduced QDM means filling a hole with an
`OA(9,57)` (which exists). If the QDM is not reduced first, turning the
QDM into an OA required an `OA(10,57)`, which we don't have.
For this reason the `OA(9,514)` was not included in the Vmt vectors, and
this branch fixes it.
The good thing is that with this branch everything is handled correctly
(and the QDM automatically reduced if needed), which means that we can add
to the Vmt database some Vmt that cannot be turned into complete OA.
Two good points:
1) I can not add another Vmt which had the same problem as this 514 thing
and creates an OA that we do not have already
2) I can now add Vmt that will produce incomplete OA that can be used by
`incomplete_orthogonal_array` to get OA with holes of size `>1`, and that
means perhaps being able to use the Brouwer-van Rees version of Wilson's
construction.
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/16884#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
