[Numpy-discussion] LU factorization?

Robert Kern robert.kern@gmail....
Wed Oct 15 15:49:31 CDT 2008


On Wed, Oct 15, 2008 at 15:33, Charles R Harris
<charlesr.harris@gmail.com> wrote:
>
> On Wed, Oct 15, 2008 at 2:26 PM, Robert Kern <robert.kern@gmail.com> wrote:
>>
>> On Wed, Oct 15, 2008 at 15:21, Charles R Harris
>> <charlesr.harris@gmail.com> wrote:
>> >
>> > On Wed, Oct 15, 2008 at 2:04 PM, Robert Kern <robert.kern@gmail.com>
>> > wrote:
>> >>
>> >> On Wed, Oct 15, 2008 at 14:49, Charles R Harris
>> >> <charlesr.harris@gmail.com> wrote:
>> >> >
>> >> > On Wed, Oct 15, 2008 at 1:06 PM, Robert Kern <robert.kern@gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> On Wed, Oct 15, 2008 at 00:23, Charles R Harris
>> >> >> <charlesr.harris@gmail.com> wrote:
>> >> >> > Hi All,
>> >> >> >
>> >> >> > numpy.linalg has qr and cholesky factorizations, but LU
>> >> >> > factorization
>> >> >> > is
>> >> >> > only available in scipy. That doesn't seem quite right. I think is
>> >> >> > would
>> >> >> > make sense to include the LU factorization in numpy among the
>> >> >> > basic
>> >> >> > linalg
>> >> >> > operations, and probably LU_solve also. Thoughts?
>> >> >>
>> >> >> -1. As far as I am concerned, numpy.linalg exists because Numeric
>> >> >> had
>> >> >> LinearAlgebra, and we had to provide it to allow people to upgrade.
>> >> >> I
>> >> >> do not want to see an expansion of functionality to maintain.
>> >> >
>> >> > I would be happier with that argument if scipy was broken into
>> >> > separately
>> >> > downloadable modules and released on a regular schedule.
>> >>
>> >> Then that is the deficiency that we should spend time on, not
>> >> duplicating the functionality again.
>> >
>> > Should we break out the linear algebra part of scipy and make it a
>> > separate
>> > package? I suspect that would add to the build burden, because we would
>> > then
>> > have a new package to maintain and release binaries for. I don't see the
>> > problem with having a bit of linear algebra as part of the numpy base
>> > package.
>>
>> Which bits? The current set has worked fine for more than 10 years.
>> Where do we stop? There will always be someone who wants just one more
>> function. And a case can always be made that adding just that function
>> is reasonable.
>
> I would just add the bits that are already there and don't add any extra
> dependencies, i.e., they are there when numpy is built without ATLAS or
> other external packages. The determinant function in linalg uses the LU
> decomposition, so I don't see why that shouldn't be available to the general
> user.

I'm softening to this argument. But mostly because it will be you who
will have to defend this arbitrary line in the sand in the future
rather than me.  :-)

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco


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