Re: [Discuss-gnuradio] Non-deterministic behavior in GNU Radio

[Ron Economos]

Well, I guess it's not really a bug. Most likely it has to do with the 
accuracy difference between the x86 intrinsics and the C library. If you 
look at the code in volk_32fc_x2_divide_32fc.h, the remaining points 
that are not a multiple of four are calculated with the C library. If 
the points from one run that are calculated with the C library line up 
with points calculated with intrinsics in the next run, there can be a 
mismatch.

Ron

On 10/03/2018 06:27 AM, Ron Economos wrote:
> It's a VOLK bug. Go into ~/.volk/volk_profile and change the 
> volk_32fc_x2_divide_32fc line to generic. That fixes the issue here.
>
> Ron
>
>
> On 10/03/2018 05:46 AM, Piotr Krysik wrote:
> > Hi all,
> >
> > I simplified the flowgraph a bit and prepared a script that runs it
> > twice and compares the results.
> >
> > https://imgur.com/a/CSjOeLc
> >
> > In short something is wrong indeed.
> > Almost after every run of the script I get results with differences.
> >
> > I tested it on GNU Radio  3.7.12.0, I'm compiling the most fresh version
> > now.
> >
> > Best Regards,
> > Piotr Krysik
> >
> > W dniu 03.10.2018 o 06:55, Reiichiro Nakano pisze:
> > > Here's an updated flowgraph where you don't need a separate file
> > > source. Just run the flowgraph twice for a few seconds each. You'll
> > > likely get different file sizes but `cmp` doesn't care, it'll still
> > > show the first differing byte which should still prove the bug exists.
>
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