[Numpy-discussion] when does numpy create temporaries ?

[Simon B. <si...@ar...>]

Consider these two operations:

>>> a=numpy.empty( 1024 )
>>> b=numpy.empty( 1024 )
>>> a[1:] = b[:-1]
>>> a[1:] = a[:-1]
>>>

It seems that in the second operation
we need to copy the view a[:-1]
but in the first operation we don't need
to copy b[:-1].

How does numpy detect this, or does it
always copy the source when assigning to a slice ?

I've poked around the (numpy) code a bit and
tried some benchmarks, but it's still not so
clear to me.

Simon.


-- 
Simon Burton, B.Sc.
Licensed PO Box 8066
ANU Canberra 2601
Australia
Ph. 61 02 6249 6940
http://arrowtheory.com