[Numpy-discussion] Regression in mpl: AttributeError: incompatible shape for a non-contiguous array

[Benjamin Root]

On Mon, Oct 29, 2012 at 11:04 AM, Patrick Marsh <patrickmarshwx at gmail.com>wrote:

> Turns out it isn't the commit I thought it was. I'm currently going
> through a git bisect to track down the actual commit that introduced this
> bug. I'll post back when I've found it.
>
>
>  PTM
> ---
> Patrick Marsh
> Ph.D. Candidate / Liaison to the HWT
> School of Meteorology / University of Oklahoma
> Cooperative Institute for Mesoscale Meteorological Studies
> National Severe Storms Laboratory
> http://www.patricktmarsh.com
>
>
>
> On Mon, Oct 29, 2012 at 9:43 AM, Benjamin Root <ben.root at ou.edu> wrote:
>
>>
>>
>> On Mon, Oct 29, 2012 at 10:33 AM, Sebastian Berg <
>> sebastian at sipsolutions.net> wrote:
>>
>>> Hey,
>>>
>>> On Mon, 2012-10-29 at 09:54 -0400, Benjamin Root wrote:
>>> > This error started showing up in the test suite for mpl when using
>>> > numpy master.
>>> >
>>> > AttributeError: incompatible shape for a non-contiguous array
>>> >
>>> > The tracebacks all point back to various code points where we are
>>> > trying to set the shape of an array, e.g.,
>>> >
>>> > offsets.shape = (-1, 2)
>>> >
>>> Could you give a hint what these arrays history (how it was created) and
>>> maybe .shape/.strides is? Sounds like the array is not contiguous when
>>> it is expected to be, or the attribute setting itself fails in some
>>> corner cases on master?
>>>
>>> Regards,
>>>
>>> Sebastian
>>>
>>>
>> The original reporter of the bug dug into the commit list and suspects it
>> was this one:
>>
>>
>> https://github.com/numpy/numpy/commit/02ebf8b3e7674a6b8a06636feaa6c761fcdf4e2d
>>
>> However, it might be earlier than that (he is currently doing a clean
>> rebuild to make sure).
>>
>> As for the history:
>>
>>             offsets = np.asanyarray(offsets)
>>             offsets.shape = (-1, 2)             # Make it Nx2
>>
>> Where "offsets" comes in from (possibly) user-supplied data.  Nothing
>> really all that special.  I will see if I can get stride information.
>>
>> Ben Root
>>
>>
Further digging reveals that the code fails when the array is originally
1-D.  I had an array with shape (2,) and stride (8,).  The reshaping should
result in a shape of (1, 2).

Ben Root
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