[Numpy-discussion] memory allocation at assignment
Travis Oliphant
travis at continuum.io
Thu Jun 28 09:28:58 EDT 2012
Yes, the creation of the tmp *is* the creation of a new NumPy array. So, it is as expensive.
Travis
--
Travis Oliphant
(on a mobile)
512-826-7480
On Jun 28, 2012, at 12:44 AM, srean <srean.list at gmail.com> wrote:
>> Yes it does. If you want to avoid this extra copy, and have a
>> pre-existing output array, you can do:
>>
>> np.add(a, b, out=c)
>>
>> ('+' on numpy array's is just a synonym for np.add; np.add is a ufunc,
>> and all ufunc's accept this syntax:
>> http://docs.scipy.org/doc/numpy/reference/ufuncs.html
>> )
>
>
> Is the creation of the tmp as expensive as creation of a new numpy
> array or is it somewhat lighter weight (like being just a data
> buffer). I sometimes use the c[:] syntax thinking I might benefit from
> numpy.array re-use. But now I think that was misguided.
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