[Numpy-discussion] Floating point exception with numpy and embedded python interpreter

[Andrew Straw]

This doesn't seem like an issue with numpy. Your test proved that. I'm
curious what the outcome is, but I'm afraid there's not much we can do.

At this point I think you should write the ns2 people and see what they
say. Their program seems to be responsible for twiddling the FPU/SSE
flags, so I think the issue is better solved, or at least discussed, by
them.

Cheers!
Andrew

Arkaitz Bitorika wrote:

> Andrew,
>
> I've verified that the function causes the exception when embedded in 
> the program but not when used from a simple C program with just a main
> () function. The successful version iterates 31 times over the for 
> loop while the crashing one fails the 30th time that it does "pinf *= 
> mul".
>
> Now we know exactly where the crash is, but no idea how to fix it ;). 
> It doesn't look it should be related to SSE2 flags, it's just doing a 
> big multiplication, but I don't know enough about low level C and 
> floating point operations to understand why it may be throwing the 
> exception there. Any idea how I could avoid that function crashing?
>
> Thanks,
> Arkaitz
>
> On 22 Apr 2006, at 20:12, Andrew Straw wrote:
>
>> OK, going back to your original gdb traceback, it looks like the  SIGFPE
>> originated in the following funtion in umathmodule.c:
>>
>> static double
>> pinf_init(void)
>> {
>>     double mul = 1e10;
>>     double tmp = 0.0;
>>     double pinf;
>>
>>     pinf = mul;
>>     for (;;) {
>>         pinf *= mul;
>>         if (pinf == tmp) break;
>>         tmp = pinf;
>>     }
>>     return pinf;
>> }
>>
>> If you try just that function (instead of the whole Python interpreter
>> and numpy module) and still get the exception, you'll be that much
>> closer to narrowing down the issue.
>