floating point exception (SIGFPE weirdness)

[Andrew Straw]

I figured out that the culprit is in the numarray.ieeespecial module, 
which my Python code imports.

The lines (taken from ieeespecial.py)

import numarray.numarrayall as _na
plus_inf = inf = _na.array(1.0)/_na.array(0.0)

are sufficient to cause the behavior in my original post.  I shall 
follow this up on the numpy discussion list.

Andrew Straw wrote:
> I'm running into trouble when calling a 3rd party library (the Intel IPP 
> library to do some fast math on a P4 processor).  This is on debian 
> linux 2.6.7 using python 2.3.4.
> 
> I've been using Pyrex to wrap my calls to this C library into an 
> extension module, and a certain function call within my extension module 
> (to the C function ippiAddWeighted_8u32f_C1IR) will terminate my Python 
> program when called for the 2nd time, with the line "Floating point 
> exception" mysteriously appearing on the console.  (Mysterious in part 
> because I can't redirect these words with piping stdout or stderr.)  I 
> should note that this function calls not only the normal Pentium 
> floating-point machinery, but should also call the SSE and SSE2 
> instruction sets.
> 
> A few clues:
> 
> 1) A trivial C program which makes the same function call repeatedly 
> with the same data is not terminated.
> 
> 2) Running the python executable under gdb causes the program to 
> continue running without terminating.
> 
> 3) The behavior (termination) is not changed after rebuilding Python 
> from source, compiling with --with-fpectl and building the fpectl 
> module, calling fpectl.turnoff_sigfpe().
> 
> I don't really understand what is happening, but I'd like my code to run 
> without terminating due to this floating point exception. My best guess 
> is that SIGFPE is being generated by the C function call, and Python 
> does not catch it so the OS terminates Python.  If this is so, however, 
> I'm not sure why Python should be terminated and why my simple C program 
> is not.  Furthermore, I don't understand why gdb doesn't see SIGFPE if 
> this is the case.
> 
> I would be very grateful if someone could tell me how to keep my program 
> running!
> 
> Cheers!
> Andrew