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

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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