#11422: modular subgroups
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Reporter: vdelecroix | Owner: vdelecroix
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.7.1
Component: modular forms | Keywords: group, arithmetic, linear
group, sl, modular
Work_issues: amusing typo bug | Upstream: N/A
Reviewer: | Author: Vincent Delecroix
Merged: | Dependencies:
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Comment(by vdelecroix):
Replying to [comment:10 davidloeffler]:
> Replying to [comment:9 vdelecroix]:
> > > Algorithm comments:
> > >
> > > - For permutation subgroups, almost all calculations are done with a
relabelled version, but this is generated anew every time! I'd suggest:
> > >
> > > - having a flag that remembers whether the group is already
canonically labelled,
> > >
> > > - when that's not the case, caching the canonically labelled
version.
> >
> > Totally right. I choose to add an attribute _canonical_label_group
when the group with canonical renumbering has been computed.
>
> There is an amusingly subtle bug here.
>
Hopefully, you find that crazy bug! Thanks! I had a supplementary doctest
for this method.
>
> I would advocate correcting the typo at line 769 but also changing the
{{{has_canonical_labels}}} function so it does what I said, i.e. so
returns True if and only if {{{self._canonical_rooted_labels() ==
range(self.index())}}}, with a docstring to match.
>
I removed the function has_canonical_labels which is not useful at all.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11422#comment:11>
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