#12916: Dedekind-MacNeil completion of finite posets
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Reporter: | Owner: sage-combinat
nthiery | Status: needs_info
Type: | Milestone: sage-wishlist
enhancement | Resolution:
Priority: minor | Merged in:
Component: | Reviewers:
combinatorics | Work issues:
Keywords: | Commit:
poset, lattice | 93cefff357a7942b4c7ea539f1d97c9b0e32acb7
Authors: | Stopgaps:
Frédéric Chapoton |
Report Upstream: N/A |
Branch: |
u/chapoton/12916 |
Dependencies: |
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Changes (by ncohen):
* status: needs_review => needs_info
Comment:
> Yes; I would even tend to get it into Sage as a provocation: any expert
reading the code will think "yikes, *I* can do sooo much better". And will
do it :-)
I am precisely the kind of guy who thought that when reading the code, and
I don't appreciate at all to see that you consider it a game to make us
rewrite other people's hasty code, just because we do not stand such waste
of computation. My time is not cheaper than anybody else's.
About this patch:
- The name of the methods that you define is not very informative:
`set_of_upper_bounds/set_of_lower_bounds` feels like you will get all `y`
greater than a given `x`. It is more 'lower_bounds_of_set`, but even then
it feels a bit awkward. Is there a word in order theory to mean "all
elements smaller than x" ? I can't even find a function that would return
that for such a vertex `x`
- Computation of the set of cuts: look at the section entitled
`Constructing the set of cuts` in the Wikipedia page that you provided.
They say that it is equivalent to list all antichains of the Poset, and
for that there is a `.antichains_iterator` function. (I wonder how it
compares with
http://www.sagemath.org/doc/reference/graphs/sage/graphs/independent_sets.html,
but that's another subject)
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/12916#comment:7>
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