[Numpy-discussion] np.dot and 'out' bug

Matthieu Brucher matthieu.brucher at gmail.com
Thu May 23 10:57:08 EDT 2013

In my point of view, you should never use an output argument equal to an
input argument. It can impede a lot of optimizations.


2013/5/23 Nicolas Rougier <Nicolas.Rougier at inria.fr>

> >
> > Sure, that's clearly what's going on, but numpy shouldn't let you
> > silently shoot yourself in the foot like that. Re-using input as
> > output is a very common operation, and usually supported fine.
> > Probably we should silently make a copy of any input(s) that overlap
> > with the output? For high-dimensional dot, buffering temprary
> > subspaces would still be more memory efficient than anything users
> > could reasonably accomplish by hand.
> Also, from a user point of view it is difficult to sort out which
> functions currently allow 'out=a' or  out=b' since nothing in the 'dot'
> documentation warned me about such problem.
> Nicolas
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