#16892: Function to check if a poset containt a subposet isomorphic to another
poset
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-wishlist
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/function_to_check_if_a_poset_containt_a_subposet_isomorphic_to_another_poset|
f13f2385d2b79adad5dae8282162d776bb8114bd
Dependencies: | Stopgaps:
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Comment (by ncohen):
Hello !!
> 1) Should I open a new ticket about `transitive_closure`? And if so,
mark it as a dependency to this one? I have no idea about what to check on
`DiGraph` class; hence, if I made a fix and you review it, it will
actually be work of only one person. If I have understood correctly, idea
is to have always two people looking at code.
I would fix it in the same ticket given that it's a very small change, but
then that's up to you if you do not feel safe fixing this yourself. It is
a fairly simple change, needed because we only recently added a support
for immutable graphs (graphs that cannot be modified) and so a lot of code
written before is not made to handle it. It is exactly the case here,
where you have to say explicitly that the copy should NOT be immutable,
even if the graph itself was immutable.
If you prefer to leave others double-check it, then indeed you should open
another ticket which would be a dependency of this one (only if you need
that bug to be fixed in order to implement what you write here).
> 2) About dokumentation: I already made an example on N5 containing
4-element diamond lattice. Would this be enought for documentation:
"Return True if the poset contains a subposet isomorphic to other. By
subposet we mean a poset containing elements with partial order induced by
that of self."?
"Induced" here seems a little too vague to me. But you could complete it
with the code you used before:
"By subposet we mean tha set {{{``X``}}} of vertices such that
`P1.subposet(X).is_isomorphic(P2)`.
I really think that it would be best to implement both features at once
(possibly with an optional 'induced' boolean parameter in the function you
add). And it would also be nice to give the user a way to obtain the copy
of P2 in P1, as they will probably want this as a certificate.
Whatever you do, the beginning of the doc of each function should be a
one-line description of what it does. Then you can describe better the
behaviour of the function.
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/16892#comment:9>
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