#17216: Poset / LatticePoset: [meet|join]matrix algorithm
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.4
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Jori Mäntysalo | Reviewers: Nathann Cohen
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/poset___latticeposet___meet_join_matrix_algorithm|
a649be931b249028ff1e5961fc948c2daf50c695
Dependencies: | Stopgaps:
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Changes (by tscrim):
* status: needs_info => needs_work
Comment:
First off, I changed the status because there was no evidence that people
had run any timings. This is why I changed it to `needs_info`. I never
trust code that ''should'' be faster to really be faster; overhead and
idiosyncrasies of python can make things slower, even if asymptotically it
is a better algorithm (my go-to example is sorting, for (very) small
lists, we just use bubble sort because of overhead). Also the algorithm to
check that the finite poset is a lattice has changed (using `has_top` and
`has_bottom` instead of the matrix).
Categories also can carry mathematical information as well, in particular
for morphisms. The issue I'm raising about why the method needs to be
deprecated is this. Suppose I have some personal code for a finite poset
that does not inherit from `FinitePoset`, but is a parent belonging to the
category of `FinitePosets`. Thus I have `is_lattice` from the category.
However, with this patch, all of a sudden my code is (horribly) broken
because I no longer have the `is_lattice` method.
There is likely some duplication from things in `FinitePoset` that should
be up in the category coming from the initial implementation of the class
and when we transitioned to using categories. So what should happen is you
should delete the method in the `FinitePoset` class (which doesn't need a
deprecation because you get it from the category).
--
Ticket URL: <http://trac.sagemath.org/ticket/17216#comment:17>
Sage <http://www.sagemath.org>
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