[Numpy-discussion] memory allocation at assignment

Travis Oliphant travis@continuum...
Thu Jun 28 08:35:48 CDT 2012



--
Travis Oliphant
(on a mobile)
512-826-7480


On Jun 28, 2012, at 1:20 AM, Pierre Haessig <pierre.haessig@crans.org> wrote:

> Le 28/06/2012 02:34, Nathaniel Smith a écrit :
>> 
>> 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)
> And is there a temporary copy when using inplace operators like:
> 
> c = a.copy()
> c += b 
> 
> Is there a temporary (c+b)  array which is then assigned to c, or is it really an inplace assignment as the operator +=  would suggest ?
> 

It really is inplace.   As Nathaniel mentioned --- all ufuncs take an out keyword.  

The inplace mechanism uses this so that one input and the output are the same.

Travis 

> Pierre
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