[Numpy-discussion] Masked Array for NumPy 1.7

Charles R Harris charlesr.harris at gmail.com
Sat May 19 10:17:04 EDT 2012

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.

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