[FFmpeg-devel] [PATCH] avfilter, swresample, swscale: use fabs, fabsf instead of FFABS

Ganesh Ajjanagadde gajjanag at mit.edu
Wed Oct 14 12:35:46 CEST 2015

On Wed, Oct 14, 2015 at 2:40 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> Ganesh Ajjanagadde <gajjanag <at> mit.edu> writes:
>> >> I think the general case, it'd be nice to figure out
>> >> why Carl's results are slightly different from yours
>> >
>> > Why do you think they are different at all?
>> > Did you look at the tables?
>> They are different, and our conclusions are different
>> (in a slight way). Carl claims that the old code and
>> new code are mostly the same in speed, but in the
>> cases where they differ, the old code is faster.
> No.
> I wrote that both the numbers you posted and the numbers
> I posted show no proof that the new code is faster.

You posted a first reply with all manner of stuff saying essentially
that "I believe the old code may be faster". You have not withdrawn
that claim, and neither have I withdrawn mine.

> (Contrary to my numbers, your numbers show that the old
> code may be faster but that is irrelevant.)

What? My numbers actually show that the new code may be faster -
again: cycle times in the best case are identical, in the worst case
they favor the new code. My random number benchmark is also clearly in
favor of the new code. How this is "irrelevant" is beyond me. Also,
please don't spin my numbers into something they are not: this is
distracting the thread. Clement and Paul have already started moving
to using the function, others are free to see the numbers themselves.
Why you are trying to derail the benchmarks I posted is beyond me.

If you continue to post such stuff that has no basis, I might actually
get tempted into finding out for which floating point values the new
code is significantly faster, craft a relevant audio file, and post it
showing a huge performance difference - my random numbers benchmark
shows there must exist such values.

> The more important question is if you can see the same
> changes in the disassembly of af_astats.o as what
> ubitux posted here for a short test function?

I do. He uses clang/gcc, so do I. The reason (irrelevant) is that both
of us run Arch.

What is "more relevant" is if _you_ can see the changes on some non
Linux platform.

> Carl Eugen
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