[SciPy-Dev] removing umfpack wrapper

[Ralf Gommers]

On Thu, Nov 14, 2013 at 11:09 PM, Robert Cimrman <cimrman3 at ntc.zcu.cz>wrote:

> On 11/14/2013 09:59 PM, Ralf Gommers wrote:
> > On Tue, Nov 12, 2013 at 11:57 PM, Robert Cimrman <cimrman3 at ntc.zcu.cz
> >wrote:
> >
> >> On 11/12/2013 11:22 PM, Ralf Gommers wrote:
> >>> On Tue, Nov 12, 2013 at 10:20 AM, Robert Cimrman <cimrman3 at ntc.zcu.cz
> >>> wrote:
> >>>
> >>>> Hi Ralf,
> >>>>
> >>>> On 11/10/2013 04:36 PM, Ralf Gommers wrote:
> >>>>> Hi all,
> >>>>>
> >>>>> This is long overdue, but I think it's time to remove the UMFPACK
> >> wrapper
> >>>>> before the next release. I'd like some feedback on how to do that and
> >> to
> >>>>> what package (if any) to point existing users.
> >>>>>
> >>>>> As for why to remove the wrapper, see:
> >>>>> https://github.com/scipy/scipy/issues/3002
> >>>>> http://permalink.gmane.org/gmane.comp.python.scientific.user/20451
> >>>>> Short summary: UMFPACK changed from a BSD-compatible license to GPL
> at
> >>>> some
> >>>>> point.
> >>>>>
> >>>>> The deprecation warning in sparse.linalg has been referring people to
> >>>>> scikits.umfpack until now, however that package has disappeared
> >>>> completely
> >>>>> as far as I can tell. I suspect it was in the old scikits svn repo
> and
> >>>> was
> >>>>> never moved before that was killed. The alternatives seems to be
> >>>> Pysparse (
> >>>>
> >>>> I missed that the scikit was lost in transition...
> >>>>
> >>>> How much work would be to move it to the new site - move from SVN to
> >> git,
> >>>> and?
> >>>> I would be willing to do it, if there is interest.
> >>>>
> >>>
> >>> Hi Robert, I think the moving wouldn't be a lot of work (assuming svn
> >>> access can still be arranged). If you'd revive the scikit it's not a
> >>> one-time effort though - it's only useful if the code is being
> maintained
> >>> imho. That can still be low effort perhaps, but with reviewing some
> PRs,
> >>> maintenance releases, putting it on pypi, etc. I'd expect at least an
> >> hour
> >>> a week or so.
> >>>
> >>> Are there scikits.umfpack users now? Would it make sense to salvage
> >>> whatever is useful from the scikit and contribute it to pysparse
> instead?
> >>
> >> We are using it in sfepy as the default direct solver. It seems to me
> that
> >> the
> >> pysparse interface requires the input matrix to be in the LL (linked
> list)
> >> format, which is unfortunate for us, as we use CSR. The scipy (and
> former
> >> scikit) umfpack wrappers have used CSR, so no copies were necessary.
> (After
> >> all, I have created the original scipy wrappers to be used from sfepy in
> >> the
> >> first place...)
> >>
> >
> > CSR is much better supported by scipy.sparse, so that's a good reason for
> > the scikits.umfpack interface to exist I'd think.
>
> Ok, so I will try to migrate it to the new scikits site.
>

Great. I'm not sure that that will live forever (who maintains it?). Just
putting the repo on Github and enabling issue tracking there, plus
uploading a release to pip, would be the essential steps.

Ralf

 >
> >> So in case others are not interested in having the scikit,
> >
> >
> > I'm not sure that's the case. Would be great to have some more feedback
> > here - I don't have a strong opinion either way.
>
> I think most people still use it transparently via the wrappers in scipy,
> without installing the (old) scikit, just like me. When the wrappers
> disappear
> they would seek a replacement.
>
> >
> >> I can see two possible solutions from my perspective: either enhance
> >> pysparse interface to
> >> allow CSR as well, or move the wrappers to sfepy (which I maintain
> anyway,
> >> but
> >> swig -> cython conversion would be needed). Not sure yet which solution
> I
> >> prefer.
> >>
> >
> > Moving them into SfePy would work for SfePy but as an optional dependency
> > for scipy that would be weird imho, given the rather heavy list of
> > dependencies of SfePy.
>
> Yes, that was just an idea for the case nobody else uses umfpack with
> scipy. I
> do not think that is true, although the users has remained silent here.
> There
> might be more feedback on scipy-user.
>
> Anyway, I will migrate the scikit so that there is a place to go after the
> removal. The maintenance should not be that demanding as the umfpack
> library
> API has been quite stable.
>
> r.
>
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