[Numpy-discussion] Learning "strides"

Sasha ndarray at mac.com
Fri Feb 3 14:05:01 CST 2006


On 2/2/06, Travis Oliphant <oliphant.travis at ieee.org> wrote:
> ...
> Here's the issue.  With records it is quite easy to generate  strides
> that are not integer multiples of the data.  For example, a record
> [('field1', 'f8),('field2', 'i2')] data-type would have floating point
> data separated by 10 bytes.  When you get a view of field1 (but getting
> that attribute) you would get such a "misaligned" data.
>
> Look at the following:
>
> temp = array([(1.8,2),(1.7,3)],dtype='f8,i2')
> temp['f1'].strides
> (10,)
>
> How would you represent that in the element-based strides report?

You are right. I cannot think of anything better than just byte-based
strides in this case.  Maybe we could add a restriction
abs(strides[i]) >= itemsize? This will probably catch some of the more
common mistakes that are due to using number of elements instead
of number of bytes.




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