On Thu, May 10, 2012 at 7:23 PM, Chris Barker <chris.bar...@noaa.gov> wrote: > That is one of my concerns about the "bit pattern" idea -- we've then > created a new binary type that no other standard software understands > -- that looks like a a lot of work to me to deal with, or even worse, > ripe for weird, non-obvious errors in code that access that good-old > char*.
Numpy supports a number of unusual binary data types, e.g. halfs and datetimes, that aren't well supported by other standard software. As Travis points out, no-one forces you to use them :-). > So I'm happier with a mask implementation -- more memory, yes, but it > seems more robust an easy to deal with with outside code. Let's say we have a no-frills C function that we want to call, and it's defined to use a mask: void do_calcs(double * data, char * mask, int size); To call this function from Cython, then in the mask NAs world we do something like: a = np.ascontiguousarray(a) do_calcs(PyArray_DATA(a), PyArray_MASK(a), a.size) OTOH in the bitpattern NA world, we do something like: a = np.ascontiguousarray(a) mask = np.isNA(a) do_calcs(PyArray_DATA(a), PyArray_DATA(mask), a.size) Of course there are various extra complexities that can come in here depending on what you want to do if there are no NAs possible, whether do_calcs can take a NULL mask pointer, if you're writing in C instead of Cython then you need to use the C equivalent functions, etc. But IMHO there's no fundamental reason why bitpatterns have to be much more complex to deal with in outside code than masks, assuming a properly helpful API. What can't be papered over at the API level are the questions like, do you want to be able to "un-assign" NA to reveal what used to be there before? That needs masks, for better or worse. But I may well be missing something... does that address your concern, or is there more to it? -- Nathaniel _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
