[Numpy-discussion] memory allocation at assignment

Travis Oliphant travis@continuum...
Thu Jun 28 08:28:58 CDT 2012


Yes,  the creation of the tmp *is* the creation of a new NumPy array.  So, it is as expensive.

Travis 

--
Travis Oliphant
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512-826-7480


On Jun 28, 2012, at 12:44 AM, srean <srean.list@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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