#17941: Automatic guess of the groups in a GDD
-------------------------------------+-------------------------------------
Reporter: brett | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.6
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: group divisible | Reviewers: Vincent Delecroix
design, block design | Work issues:
Authors: Nathann Cohen | Commit:
Report Upstream: N/A | 884a359e7b5cf4d65000bbf67d9fa4aaf63c7bdb
Branch: public/17941 | Stopgaps:
Dependencies: |
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Changes (by ncohen):
* status: needs_info => needs_review
Comment:
Hello,
> Shouldn't
> {{{
> if matrix[i*n+j] == 0:
> ...
> }}}
> be
> {{{
> if matrix[i*n+j] < l:
> ...
> }}}
Both work. Consider the whole matrix: for the design to be a GDD, it must
have two types of entries only: `0` or `l`.
1) If the matrix is a real GDD, you can see that the two are equivalent
2) If the matrix is not a GDD, the 'error' message will differ. (wrong
size of groups, or a pair not present the right number of times, or two
points of a group contained in the same set, ...)
> This suggest to add an example with `lambd > 1`.
Do you have an example in mind?
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/17941#comment:6>
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