Possible bug (was Re: numpy, overflow, inf, ieee, and rich comparison)

[David M. Cooke]

At some point, hzhu at yahoo.com (Huaiyu Zhu) wrote:

> On Wed, 11 Oct 2000 22:44:20 -0400, Tim Peters <tim_one at email.msn.com> wrote:
> 
> >Apparently Python on libc+glibc+Linux never raised OverflowError from math.*
> >functions in 1.5.2 (although it did on most other platforms I know about).
> 
> Is it just glibc or is it glibc+Linux?  Here's test on my machine
> 
> Without -lieee
>   x       exp(x)     errno   errmessage
> -745.0  4.94066e-324    0    Success
> -746.0             0   34  Numerical result out of range
>  709.0  8.21841e+307   34  Numerical result out of range
>  710.0           inf   34  Numerical result out of range
> sqrt( -1.0) =   nan,   33  Numerical argument out of domain
>     
> On all the other platforms, what happens when you use ieee confirming flags?
> I'd bet they behave pretty much the same.  Anyone on other platform care to
> check out?  Here's the C program

Even on glibc+Linux, it depends on the optimizations: for my machine
running Linux-Mandrake 7.1 (glibc 2.1.3):

Without -lieee, and without -O, I get your results above.

Without -lieee, but compiled with -O, I get
  x       exp(x)     errno   errmessage
-745.0  4.94066e-324    0    Success
-746.0             0    0    Success
 709.0  8.21841e+307    0    Success
 710.0           inf    0    Success
sqrt( -1.0) =   nan,    0    Success

However, on my Debian machine (with glibc 2.1.94) I get the first
behaviour for compiling with -O (and higher). The compilers are both
gcc 2.95.2.

This is the reason exp behaves differently in Python on my work
machine (with Linux-Mandrake) and on my home machine (with Debian):
Mandrake compiles Python with optimizations (more severe than -O).
This was a pain in the a** for some numerical code I was writing.

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David M. Cooke
cookedm at physics.mcmaster.ca