#16884: A database entry for Quasi-difference matrices
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Reporter: ncohen | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.4
Component: combinatorial designs | Keywords:
Merged in: | Authors: Nathann Cohen
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies: #16879
Stopgaps: |
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A new database entry for quasi-difference matrices. As a result:
- The Vmt vectors are added to the quasi-difference matrices database
entry, and not anymore to `OA_constructions`
- The old OA constructions based on QDM are converted to QDM constructors.
- The OA constructor now queries the QDM database entry (and so it gets
the QDM+Vmt)
Two notes:
- There is no `is_quasi_difference_matrix` right now, so the QDM are
tested through the OA they generate.
- There is no `designs.quasi_difference_matrix` because I did not know how
to write it in such a way that it would be easy to find a QDM that builds
an OA. The problem is that a QDM is defined with 5 parameters
`(n,_,_,_,u)` and that the `n` of an `OA(k,n)` is the sum `n+u`.
Consequently, if you want to build an `OA(k,n)` from a QDM you must try
all pairs `n'+u = n` and that's a waste of time.
- Right now the DM are not added to the dictionary of QDM. I did not see
the point, given that the DM are already queried by `orthogonal_arrays()`
through their constructor (which will also contain additional
constructions of DM).
--
Ticket URL: <http://trac.sagemath.org/ticket/16884>
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