On Fri, Dec 25, 2015 at 9:47 AM, Hendrik Leppkes <h.lepp...@gmail.com> wrote: > On Fri, Dec 25, 2015 at 6:27 PM, Ganesh Ajjanagadde <gajja...@mit.edu> wrote: >> On Fri, Dec 25, 2015 at 9:26 AM, James Almer <jamr...@gmail.com> wrote: >>> On 12/25/2015 2:11 PM, Ganesh Ajjanagadde wrote: >>>> Fast, reasonably accurate 10^x. Alternative of detection of libm exp10 at >>>> configure >>>> time is not worth the trouble, since it is anyway not POSIX or ISO C, >>>> and currently only the GNU libm has it. Furthermore, GNU libm's variant >>>> is ~ 2x slower, and is ironically not correctly rounded (2 ulp off) to >>>> justify all >>>> that slowdown. >>>> >>>> Reviewed-by: Michael Niedermayer <mich...@niedermayer.cc> >>>> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> >>>> --- >>>> libavutil/internal.h | 19 +++++++++++++++++++ >>>> 1 file changed, 19 insertions(+) >>>> >>>> diff --git a/libavutil/internal.h b/libavutil/internal.h >>>> index f86b7fb..ae11601 100644 >>>> --- a/libavutil/internal.h >>>> +++ b/libavutil/internal.h >>>> @@ -292,6 +292,25 @@ static av_always_inline av_const int64_t >>>> ff_rint64_clip(double a, int64_t amin, >>>> return res; >>>> } >>>> >>>> +/** >>>> + * Compute 10^x for floating point values. Note: this function is by no >>>> means >>>> + * "correctly rounded", and is meant as a fast, reasonably accurate >>>> approximation. >>>> + * For instance, maximum relative error for the double precision variant >>>> is >>>> + * ~ 1e-13 for very small and very large values. >>>> + * This is ~2x faster than GNU libm's approach, which is still off by >>>> 2ulp on >>>> + * some inputs. >>>> + * @param x exponent >>>> + * @return 10^x >>>> + */ >>>> +static av_always_inline double avpriv_exp10(double x) >>> >>> It's an inline function in a header, and internal at that. Just call it >>> ff_exp10. >> >> It is used in avcodec and avfilter. I thought this meant that it >> should be avpriv? >> Personally, I like ff_exp10 as it is shorter. >> > > avpriv is a hack for private functions that need to be exported in > shared libraries, since we have a rule to only export av* functions.
Makes sense now. > inline functions in headers don't need to be exported in a library, so > no need for avpriv. ff* is fine there, and used for other similar > situations. Guess the patch is ok (once this is changed), and likewise the configure one. Both of these going in soon. Thanks. > > - Hendrik > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
