[Numpy-discussion] Different results from repeated calculation

Fernando Perez fperez.net at gmail.com
Sat Jan 27 17:52:35 CST 2007


On 1/27/07, Robert Kern <robert.kern at gmail.com> wrote:
> Fernando Perez wrote:
>
> > That's it.  One comment char removed, and something that's done
> > /after/ the tests are actually executed.
> >
> > That kind of 'I add a printf() call and the bug disappears' is
> > unpleasantly reminiscent of lurking pointer errors in C code...
>
> Heh. Fantastic. It might be worthwhile porting this code to C to see what
> happens. If we can definitively point the finger at the kernel, that would be
> great (less work for me!).


It's definitely looking like something SMP related: on my laptop, with
everything other than the hardware being identical (Linux distro,
kernel, numpy build, etc), I can't make it fail no matter how I muck
with it.  I always get '0 differences'.

The desktop is a dual-core AMD Athlon as indicated before, the laptop
is an oldie Pentium III.  They both run the same SMP-aware Ubuntu i686
kernel, since Ubuntu now ships a unified kernel, though obviously on
the laptop the SMP code isn't active.

Cheers,

f


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