#16553: Clean IncidenceStructure
-------------------------------------+-------------------------------------
Reporter: vdelecroix | 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:
Vincent Delecroix | Commit:
Report Upstream: N/A | b8012e72038dffa51cc60b0af19283881dec2860
Branch: public/16553v2 | Stopgaps:
Dependencies: |
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Comment (by vdelecroix):
Replying to [comment:75 ncohen]:
> Okay, three questions :
>
> - Should !BlockDesign be deprecated ?
It is cool to have as an alias for incidence structure. If you find
confusing to have an alias, then yes we should deprecate it.
> - is `self._degrees_cache` used anywhere ? If not, remove it
Not anymore. I will.
> - `self._incidence_matrix` is set to None even when the Incidence
Structure has been defined from the incidence matrix
Yes, because of the reordering of the columns. But we can avoid reordering
the columns and keep the matrix. But then, matrices are mutable...
hopefully, we can do `m.set_immutable()` as soon as we use it.
> - `is_simple()` does not work when the input is not copied and not
necessarily sorted.
And the implementation is stupid, if the blocks are sorted, one would do
{{{
B = self._blocks
return any(B[i] == B[i+1] for i in xrange(len(B)-1))
}}}
And... Haaaa.... it is very bad to reorder the blocks:
{{{
sage: D = designs.IncidenceStructure(2, [[0]])
sage: D == D.dual().dual()
False
}}}
Taking dual should just be matrix transposition!! One question: what do
you think of '''not''' reordering the blocks? (which is a different from
the question "sorting each block")
Vincent
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Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:79>
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