On Fr, 2015-01-30 at 19:52 -0800, Jaime Fernández del Río wrote:
On Thu, Jan 29, 2015 at 8:57 AM, Nathaniel Smith <njs@pobox.com> wrote: On Thu, Jan 29, 2015 at 12:56 AM, Jaime Fernández del Río <jaime.frio@gmail.com> wrote: [...]
<snip>
Could we make it more like: check to see if the last dimension works. If not, raise an error (and let the user transpose some other dimension there if that's what they wanted)? Or require the user to specify which dimension will absorb the shape change? (If we were doing this from scratch, then it would be tempting to just say that we always add a new dimension at the end with newtype.itemsize / oldtype.itemsize entries, or absorb such a dimension if shrinking. As a bonus, this would always work, regardless of contiguity! Except that when shrinking the last dimension would have to be contiguous, of course.)
When we roll @ in and people start working with stacks of matrices, we will probably find ourselves having to create an alias, similar to .T, for .swapaxes(-1, -2). Searching for the smallest stride allows to take views of such arrays, which does not work right now because the array is no longer contiguous globally.
That is true, but I agree with Nathaniel at least as far as that I would prefer a user to be able to safely use `view` even he has not even an inkling about what his memory layout is. One option would be an `axis=-1` default (maybe FutureWarn this from `axis=None` which would look at order, see below -- or maybe have axis='A', 'C' and 'F' and default to 'A' for starters). This even now could start creating bugs when enabling relaxed strides :(, because your good old fortran order complex array being viewed as a float one could expand along the wrong axis, and even without such arrays swap order pretty fast when operating on them, which can create impossibly to find bugs, because even a poweruser is likely to forget about such things. Of course you could argue that view is a poweruser feature and a user using it should keep these things in mind.... Though if you argue that, you can almost just use `np.ndarray` directly ;) -- ok, not really considering how cumbersome it is, but still. - Sebastian
I guess the main consideration for this is that we may be stuck with stuff b/c of backwards compatibility. Can you maybe say a little bit about what is allowed now, and what constraints that puts on things? E.g. are we already grovelling around in strides and picking random dimensions in some cases?
Just to restate it: right now we only allow new views if the array is globally contiguous, so either along the first or last dimension.
Jaime
-n
-- Nathaniel J. Smith Postdoctoral researcher - Informatics - University of Edinburgh http://vorpus.org _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
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