[FFmpeg-devel] [PATCH 09/10] avfilter/vsrc_mandelbrot: use hypot()

Nicolas George george at nsup.org
Mon Nov 23 18:54:16 CET 2015

Le tridi 3 frimaire, an CCXXIV, Ganesh Ajjanagadde a écrit :
> It seems like getting rid of the sqrt altogether has a very slight
> positive impact (if any at all). I can post the patch, but would like
> to know what to benchmark. There are numerous choices, e.g
> draw_mandelbrot as a whole, the outer loop, or the inner loop.
> I personally think the inner x loop (lines 268-388) is a good place to
> look at, since the difference is very small anyway, and further
> localization is impossible.

The smallest unit that is usually (or always) called as a whole. Otherwise,
you may find you did shave 10 cycles on a 30 cycles task that is always
called after a 100M cycles task, and find speed ×1.5 instead of negligible.

In this case, that would be draw_mandelbrot(), and you can do the benchmark
using just ffmpeg.c and the shell's timing utilities.

(You made the same mistake for deshake.)


  Nicolas George
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