[Numpy-discussion] [Repost] Adding the arrays returned in an array iterator

[srean]

Bumping my question tentatively. I am fairly sure there is a good answer and
for some reason it got overlooked.

Regards
  srean

---------- Forwarded message ----------
From: srean <srean.list at gmail.com>
Date: Fri, May 27, 2011 at 10:36 AM
Subject: Adding the arrays in an array iterator
To: Discussion of Numerical Python <numpy-discussion at scipy.org>


Hi List,

 I have to sum up an unknown number of ndarrays of the same size. These
arrays, possibly thousands in number, are provided via an iterator. Right
now I use python reduce with operator.add.

 Does that invoke the corresponding ufunc internally ? I want to avoid
creating temporaries, which I suspect a naive invocation of reduce will
create.  With ufunc I know how to avoid making copies using the output
parameter, but not sure how to make use of that in reduce.

 It is not essential that I use reduce though, so I would welcome idiomatic
and efficient way of executing this. So far I have stayed away from building
an ndarray object and summing across the relevant dimension. Is that what I
should be doing ?  Different invocations of this function has different
number of arrays, so I cannot pre-compile away this into a numexpr.

Thanks and regards
  srean
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