#14126: Count Number of Linear Extensions of a Poset
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Reporter: csar | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: combinatorics | Resolution:
Keywords: days45 | Merged in:
Authors: Jori Mäntysalo | Reviewers:
Report Upstream: N/A | Work issues:
Branch: u/jmantysalo | Commit:
/count-lin-ext | 24bc3319d440b0172666a2cace440e20986e91b6
Dependencies: | Stopgaps:
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Comment (by kdilks):
Replying to [comment:38 jmantysalo]:
> Does that mean that `order_ideals_lattice()` will have an option to get
a lattice with plain integers as elements? If so, we should now deprecate
`as_ideal` keyword, as it is plain Boolean value. Or at least it sounds
funny to have `as_ideal` with possible values `True`, `False` and
`'integers'`.
Yes. It probably makes sense to deprecate `as_ideals`, and change it to a
keyword like `representative` that defaults to `ideal`, but can also be
`antichains` or `integers`.
I guess I'd want to quantify how much overhead calculating connected
components and a series-parallel decomposition of the original Hasse
diagram introduces (my guess is a little and lot, respectively) before
making it part of every single computation. I feel like unless you
explicitly construct something as an ordinal/disjoint sum of smaller
posets (and thus should already know the decomposition), almost every
poset you'd throw at this where you'd really need optimal performance is
going to be connected and not have a series-parallel decomposition.
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Ticket URL: <https://trac.sagemath.org/ticket/14126#comment:41>
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