[Numpy-discussion] floating point exception weirdness

[Andrew Straw]

Hi All,

I've isolated numarray.ieeespecial as the cause of a strange error which 
I posted on c.l.py:
http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=41198B29.7090600%40NOSPAM-DELETE-THIS.astraw.com&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26group%3Dcomp.lang.python

My non-expert guess as to an explanation: some statements early in 
numarray.ieeespecial (e.g. _na.array(1.0)/_na.array(0.0)) result in a 
floating point exception being set which lies dormant until I call 
certain functions in the Intel IPP library (e.g. 
ippiAddWeighted_8u32f_C1IR), at which point the latent exception bit my 
Python program is killed while the console says "Floating point exception".

I've come to this tentative conclusion based on 3 minimal Pyrex programs:

---------------------------------------------------- Version 1:
import numarray.numarrayall as _na
plus_inf = inf = _na.array(1.0)/_na.array(0.0)

cimport avg
avg.work() # calls IPP, terminates with "Floating point exception".
---------------------------------------------------- Version 2:
import numarray.numarrayall as _na

# Define *ieee special values*
_na.Error.pushMode(all="ignore")
plus_inf = inf = _na.array(1.0)/_na.array(0.0)
_na.Error.popMode()

cimport avg
avg.work() # calls IPP, terminates with "Floating point exception".
---------------------------------------------------- Version 3:
import numarray.numarrayall as _na
cimport avg
avg.work() # calls IPP, terminates normally

In the short term, I'll try and work around this problem by not 
importing numarray.ieeespecial, but in the long term, I think we should 
try and fix this.  I'm happy to try to debug further if someone gives me 
advice on where to go from here.

Cheers!
Andrew