Re: [Discuss-gnuradio] ffast-math

[Chris Kuethe]

To be fair, I was running on a 1GHz Cortex-A8, that only had vfp3 (https://en.wikipedia.org/wiki/CHIP_(computer)#CHIP). I fully expect that you're going to need to spend some time going through all the different compiler flags (-Ofast, -march, -mcpu, -mtune, -ffast-math, -fthis-that-and-the-other) to figure out whether or not any knob makes the program run faster on that particular board, makes it use more efficient cpu instructions, or makes it produce (un)?acceptable solutions. Test suites are awesome.

Re: dump1090, I ran my test with the mutability version and since then I've switched to the flightaware fork since I run a few "piaware" sensors.

On Tue, Sep 3, 2019 at 9:59 AM Albin Stigö <address@hidden> wrote:

In my experience VOLK runs about 10% faster on Raspberry Pi 4 with
-ffast-math, depending on the flowgraph you might get more. Three
kernels had some minor problems with precision, but I think they can
be fixed so all will pass... The fun thing about these embedded
platforms is that the possibilities for optimizations are almost
endless!

On a side note, which fork of dump1090 should I run? There seems to be so many!


--Albin

On Tue, Sep 3, 2019 at 6:18 PM Chris Kuethe <address@hidden> wrote:
>
> Yep, on some processors with some workloads it really makes a huge difference. As others have commented, there may be significant trade-offs with regard to numerical behaviro.
>
> Some of my observations:
> dump1090 loses accuracy below the 7th digit when calculating precision, but consumes 10% less power on the device under test
> rtl_433 runs about 35% faster
> and acarsdec runs over 400% faster.
>
>
> On Sun, Sep 1, 2019, 07:11 Albin Stigö <address@hidden> wrote:
>>
>> Anyone has experience with the real world impact of using gcc -ffast-math with SDR in general, and GNURadio/Volk in particular?
>>
>>
>> --Albin SM6WJM
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>> Discuss-gnuradio mailing list
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--

GDB has a 'break' feature; why doesn't it have 'fix' too?