[Numpy-discussion] Masked Array for NumPy 1.7

David Cournapeau cournape at gmail.com
Sat May 19 11:00:41 EDT 2012

On Sat, May 19, 2012 at 3:17 PM, Charles R Harris <charlesr.harris at gmail.com
> wrote:

> On Fri, May 18, 2012 at 3:47 PM, Travis Oliphant <travis at continuum.io>wrote:
>> Hey all,
>> After reading all the discussion around masked arrays and getting input
>> from as many people as possible, it is clear that there is still
>> disagreement about what to do, but there have been some fruitful
>> discussions that ensued.
>> This isn't really new as there was significant disagreement about what to
>> do when the masked array code was initially checked in to master.   So, in
>> order to move forward, Mark and I are going to work together with whomever
>> else is willing to help with an effort that is in the spirit of my third
>> proposal but has a few adjustments.
>> The idea will be fleshed out in more detail as it progresses, but the
>> basic concept is to create an (experimental) ndmasked object in NumPy 1.7
>> and leave the actual ndarray object unchanged.   While the details need to
>> be worked out here,  a goal is to have the C-API work with both ndmasked
>> arrays and arrayobjects (possibly by defining a base-class C-level
>> structure that both ndarrays inherit from).     This might also be a good
>> way for Dag to experiment with his ideas as well but that is not an
>> explicit goal.
>> One way this could work, for example is to have PyArrayObject * be the
>> base-class array (essentially the same C-structure we have now with a
>> HASMASK flag). Then, the ndmasked object could inherit from PyArrayObject *
>> as well but add more members to the C-structure.     I think this is the
>> easiest thing to do and requires the least amount of code-change.      It
>> is also possible to define an abstract base-class PyArrayObject * that both
>> ndarray and ndmasked inherit from.     That way ndarray and ndmasked are
>> siblings even though the ndarray would essentially *be* the PyArrayObject *
>> --- just with a different type-hierarchy on the python side.
>> This work will take some time and, therefore, I don't expect 1.7 to be
>> released prior to SciPy Austin with an end of June target date.   The
>> timing will largely depend on what time is available from people interested
>> in resolving the situation.   Mark and I will have some availability for
>> this work in June but not a great deal (about 2 man-weeks total between
>> us).    If there are others who can step in and help, it will help
>> accelerate the process.
> This will be a difficult thing for others to help with since the concept
> is vague, the design decisions seem to be in your and Mark's hands, and you
> say you don't have much time. It looks to me like 1.7 will keep slipping
> and I don't think that is a good thing. Why not go for option 2, which will
> get 1.7 out there and push the new masked array work in to 1.8? Breaking
> the flow of development and release has consequences, few of them good.

Agreed. 1.6.0 was released one year ago already, let's focus on polishing
what's in there *now*. I have not followed closely what the decision was
for a LTS release, but if 1.7 is supposed to be it, that's another argument
about changing anything there for 1.7.

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