[SciPy-dev] erf, erfc and ndtr on OS X
Tobias Wood
twood at doc.ic.ac.uk
Fri May 1 13:55:15 EDT 2009
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
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