[SciPy-dev] erf, erfc and ndtr on OS X

[Tobias Wood]

Hi,
I'm not sure whether this should go to the dev or users list, so sorry if  
it is in the wrong place. I'm using the lastest SVN Numpy/Scipy checkouts  
with Python 2.6 on Mac OS 10.5. I was trying to use the ndtr function in  
scipy.special and discovered that it returned 0.5 for all input values  
except +/-Inf. A little bit of searching pulled up the following bug  
ticket:
http://projects.scipy.org/scipy/ticket/899
which hasn't been closed yet (I can't find any mention of it on the  
mailing lists though). I'd just like to report that I did manage to get  
erf and ndtr to return correct values by forcing the compiler to use the  
floating point constant values defined between #ifdef/endif UNK in both  
ndtr.c and const.c in scipy/special/cephes. I'm not totally sure which  
branch of the #ifdefs my compiler was going down before - is there an easy  
way to check? - but the constants it was getting were clearly wrong. SQRTH  
(1 over root 2) was defined as 0 previously.
What is the likelihood of this being fixed in the SVN repository? I am  
happy to help in constructing a patch but don't understand the  
relationship between Cephes and Scipy.
Thanks,
Toby Wood