[Numpy-discussion] 2 bugs related to isinf and isfinite generate crazy warnings

David david@silveregg.co...
Wed Jun 2 22:00:25 CDT 2010


On 06/03/2010 10:11 AM, Eric Firing wrote:
> http://www.mail-archive.com/numpy-discussion@scipy.org/msg23912.html
>
> On some systems--but evidently not for most numpy users, or there would
> have been a steady stream of screams--the appearance of np.inf in any
> call to np.isfinite or np.isinf yields this:
>
> In [1]:import numpy as np
>
> In [2]:np.isinf(np.inf)
> Warning: invalid value encountered in isinf
> Out[2]:True
>
>
> This generates streams of warnings if np.isinf or np.isfinite is applied
> to an array with many inf values.
>
> The problem is a combination of two bugs:
>
> 1) When building with setup.py, but perhaps not with scons (which I
> haven't tried yet), NPY_HAVE_DECL_ISFINITE and friends are never
> defined, even though they should be--this is all on ubuntu 10.4, in my
> case, and isfinite and isinf most definitely are in math.h.  It looks to
> me like the only mechanism for defining these is in SConstruct.

Actually, there is a bug in setup.py to detect those for python >= 2.6, 
I have fixed this.

>
> 2) So, with no access to the built-in isinf etc., npy_math.h falls back
> on the compact but slow macros that replace the much nicer ones that
> were in numpy a year or so ago.

Which one are you thinking about: the ones using fpclassify ? Could you 
show the code where the current version is slower ?

cheers,

David


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