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

Ganesh Ajjanagadde gajjanag at mit.edu
Thu Oct 15 12:53:51 CEST 2015


On Thu, Oct 15, 2015 at 6:50 AM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> On Thu, Oct 15, 2015 at 12:41 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
>> On Thu, Oct 15, 2015 at 6:37 AM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>>> On Thu, Oct 15, 2015 at 12:34 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
>>>> On Wed, Oct 14, 2015 at 6:50 AM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>>>>> On Wed, Oct 14, 2015 at 12:37 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
>>>>>> On Wed, Oct 14, 2015 at 5:01 AM, Matt Oliver <protogonoi at gmail.com> wrote:
>>>>>>> On 14 October 2015 at 09:46, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
>>>>>>>
>>>>>>>> On Tue, Oct 13, 2015 at 9:12 AM, Ganesh Ajjanagadde <gajjanag at mit.edu>
>>>>>>>> wrote:
>>>>>>>> > On Tue, Oct 13, 2015 at 4:02 AM, Clément Bœsch <u at pkh.me> wrote:
>>>>>>>> >> On Tue, Oct 13, 2015 at 09:25:03AM +0200, Paul B Mahol wrote:
>>>>>>>> >> [...]
>>>>>>>> >>> What about fmax/FFMAX?
>>>>>>>> >>
>>>>>>>> >> Feel free to try that out (it looks OT regarding the patch), but fmax()
>>>>>>>> >> looks glibc specific
>>>>>>>>
>>>>>>>> Seems they are actually ISO:
>>>>>>>> http://en.cppreference.com/w/c/numeric/math/fmax
>>>>>>>>
>>>>>>>> Can someone check availability on all of our platforms of interest
>>>>>>>> (e.g Microsoft)?
>>>>>>>>
>>>>>>>
>>>>>>> fmax and fmin are only available on msvc using 2013 or newer. Currently the
>>>>>>> only msvc version without fmax/fmin that FFmpeg supports is 2012 which uses
>>>>>>> the C99 to C89 converter.
>>>>>>
>>>>>> And does that converter handle fmin, fmax, fmaxf, etc?
>>>>>> Does it need patches?
>>>>>> Bottom line: are they safe to use at the moment?
>>>>>>
>>>>>
>>>>> No, they are not.
>>>>>
>>>>> One thing I don't understand - why are we bothering with something
>>>>> that at best comes out as "same speed" from tests performed? (low
>>>>> number of runs are irrelevant as they are not statistically
>>>>> significant).
>>>>
>>>> Because if you actually bothered to run my random numbers benchmark
>>>> instead of posting with no basis claiming "statistical
>>>> insignificance", or for that matter matter bothered to actually check
>>>> the libc link, or even looked at Clement's asm test - you would
>>>> finally understand.
>>>>
>>>> Also, what needs to be done to get fmax, fmin, etc into the converter?
>>>>
>>>
>>> The converter doesn't provide any functions, just alters the syntax if
>>> needed. Functions not available cannot be fixed that way, sorry.
>>
>> Thanks for clarifying. I am still confused: how do we have llabs then?
>> Per MSDN, this was not present in MSVC 2012, and was added in MSVC
>> 2013 (looks like a similar case to fabs, fabsf).
>>
>
> Docs appear to be wrong in that particular case. It happens sometimes
> that functions are available but didn't get added to the docs.

But with respect to fmin, fmax, etc - they were not available in 2012,
and the docs are right? Are you sure, and have you tested?

>
> - Hendrik
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