[SciPy-Dev] removing umfpack wrapper

[Robert Cimrman]

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...)

So in case others are not interested in having the scikit, 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.

Cheers,
r.

> Cheers,
> Ralf
>> 
>> Cheers,
>> r.
>> 
>>> http://pysparse.sourceforge.net) and PyUBlasExt (
>>> https://pypi.python.org/pypi/PyUblasExt). Scikits.sparse is dead(-ish)
>> and
>>> doesn't wrap umfpack it looks like. PyUBlasExt has something that looks
>>> like a wrapper but for C++ (?). So can we refer people to pysparse?
>>> 
>>> Other question: do we call Pysparse instead of scikits.umfpack when
>>> available? And if so, by default or not? Or do we rip out everything that
>>> sits under useUmfpack=True?
>>> 
>>> Cheers,
>>> Ralf