#18910: Boost minimum spanning tree
-------------------------------------+-------------------------------------
Reporter: borassi | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.8
Component: graph theory | Resolution:
Keywords: Boost, minimum | Merged in:
spanning tree | Reviewers:
Authors: Michele Borassi | Work issues:
Report Upstream: N/A | Commit:
Branch: | 4bbb2980aab4b0a81fc07cf62afa5395ee7719c1
u/borassi/boost_minimum_spanning_tree| Stopgaps:
Dependencies: #18876, #18906 |
-------------------------------------+-------------------------------------
Comment (by Rudi):
Replying to [comment:14 ncohen]:
> Stefan, Rudi? Does it look okay to you if by changing the behaviour of a
graph spanning tree routine, the output of
> {{{
> sage: Z = lift_cross_ratios(A, to_sixth_root_of_unity)
> }}}
>
> at line 416 of matroids/utilities.py changes like that?
> {{{
> Failed example:
> Z
> Expected:
> [ 1 0 1 1 1]
> [ 1 1 0 0 z]
> [ 0 1 -z -1 0]
> Got:
> [ 1 0 1 1 1]
> [ 1 1 0 0 z]
> [ 0 z - 1 1 -z + 1 0]
> }}}
>
> It may be caused by a different spanning tree, or by a reordering of its
edges.
Yes, that looks OK. This output matrix Z is fixed up to scaling of rows
and columns, and the tree is used to determine the scaling. Looks like in
this example the bottom row is scaled by z-1 (which happens to equal
-z^-1^ in that ring, z is is a sixth root of unity).
So it's safe to just update the output of the test.
--
Ticket URL: <http://trac.sagemath.org/ticket/18910#comment:15>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
