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

2013-05-23 Thread Sebastian Berg
On Thu, 2013-05-23 at 15:42 +0100, Nathaniel Smith wrote: > On Thu, May 23, 2013 at 3:19 PM, Matthieu Brucher > wrote: > > Hi, > > > > It's to be expected. You are overwritten one of your input vector while it > > is still being used. > > So not a numpy bug ;) > > Sure, that's clearly what's goin

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

2013-05-23 Thread Chris Barker - NOAA Federal
On Thu, May 23, 2013 at 7:19 AM, Matthieu Brucher wrote: > It's to be expected. You are overwritten one of your input vector while it > is still being used. > So not a numpy bug ;) It's a doc bug, at least. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/

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

2013-05-23 Thread josef . pktd
On Thu, May 23, 2013 at 11:14 AM, Nathaniel Smith wrote: > On Thu, May 23, 2013 at 3:57 PM, Matthieu Brucher > wrote: >> In my point of view, you should never use an output argument equal to an >> input argument. It can impede a lot of optimizations. > > This is a fine philosophy in some cases, b

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

2013-05-23 Thread Nicolas Rougier
> Can you file a bug in the bug tracker so this won't get lost? Done. ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion

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

2013-05-23 Thread Nathaniel Smith
On Thu, May 23, 2013 at 3:57 PM, Matthieu Brucher wrote: > In my point of view, you should never use an output argument equal to an > input argument. It can impede a lot of optimizations. This is a fine philosophy in some cases, but a non-starter in others. Python doesn't have optimizations in th

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

2013-05-23 Thread Matthieu Brucher
In my point of view, you should never use an output argument equal to an input argument. It can impede a lot of optimizations. Matthieu 2013/5/23 Nicolas Rougier > > > > > Sure, that's clearly what's going on, but numpy shouldn't let you > > silently shoot yourself in the foot like that. Re-us

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

2013-05-23 Thread Nicolas Rougier
> > 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 h

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

2013-05-23 Thread Nathaniel Smith
On Thu, May 23, 2013 at 3:19 PM, Matthieu Brucher wrote: > Hi, > > It's to be expected. You are overwritten one of your input vector while it > is still being used. > So not a numpy bug ;) Sure, that's clearly what's going on, but numpy shouldn't let you silently shoot yourself in the foot like t

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

2013-05-23 Thread Matthieu Brucher
Hi, It's to be expected. You are overwritten one of your input vector while it is still being used. So not a numpy bug ;) Matthieu 2013/5/23 Pierre Haessig > Hi Nicolas, > > Le 23/05/2013 15:45, Nicolas Rougier a écrit : > > if I use either a or b as output, results are wrong (and nothing in

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

2013-05-23 Thread Pierre Haessig
Hi Nicolas, Le 23/05/2013 15:45, Nicolas Rougier a écrit : > if I use either a or b as output, results are wrong (and nothing in the dot > documentation prevents me from doing this): > > a = np.array([[1, 2], [3, 4]]) > b = np.array([[1, 2], [3, 4]]) > np.dot(a,b,out=a) > > -> array([[ 6, 20], >

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

2013-05-23 Thread Nicolas Rougier
Hi, >From the dot documentation, I tried something simple: a = np.array([[1, 2], [3, 4]]) b = np.array([[1, 2], [3, 4]]) np.dot(a, b) -> array([[ 7, 10], [15, 22]]) And I got expected result but if I use either a or b as output, results are wrong (and nothing in the dot documentatio