On Mon, Nov 23, 2015 at 1:02 PM, Michael Niedermayer <michae...@gmx.at> wrote: > On Mon, Nov 23, 2015 at 12:43:52PM -0500, Ganesh Ajjanagadde wrote: >> On Sun, Nov 22, 2015 at 3:56 PM, Ganesh Ajjanagadde <gajja...@mit.edu> wrote: >> > On Sun, Nov 22, 2015 at 3:07 PM, Michael Niedermayer <michae...@gmx.at> >> > wrote: >> >> On Sun, Nov 22, 2015 at 12:05:49PM -0500, Ganesh Ajjanagadde wrote: >> >>> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> >> >>> --- >> >>> libavfilter/vsrc_mandelbrot.c | 2 +- >> >>> 1 file changed, 1 insertion(+), 1 deletion(-) >> >>> >> >>> diff --git a/libavfilter/vsrc_mandelbrot.c >> >>> b/libavfilter/vsrc_mandelbrot.c >> >>> index 950c5c8..a0c101e 100644 >> >>> --- a/libavfilter/vsrc_mandelbrot.c >> >>> +++ b/libavfilter/vsrc_mandelbrot.c >> >>> @@ -291,7 +291,7 @@ static void draw_mandelbrot(AVFilterContext *ctx, >> >>> uint32_t *color, int linesize, >> >>> >> >>> use_zyklus= (x==0 || s->inner!=BLACK ||color[x-1 + >> >>> y*linesize] == 0xFF000000); >> >>> if(use_zyklus) >> >>> - epsilon= scale*1*sqrt(SQR(x-s->w/2) + >> >>> SQR(y-s->h/2))/s->w; >> >>> + epsilon= scale*hypot(x-s->w/2, y-s->h/2)/s->w; >> >> >> >> old: >> >> 704 decicycles in hypo, 1048570 runs, 6 skips >> >> >> >> new: >> >> 1075 decicycles in hypo, 1048566 runs, 10 skips >> >> >> >> that is from START/STOP_TIMER over hypot() >> >> >> >> the code is speed relevant as its executed per pixel >> > >> > Thanks for testing. Looking more closely, I see no reason for >> > expensive sqrt calls anyway: one can simply square both sides; it >> > should be cheaper. Will rework, post benchmark if it is indeed faster >> > and does not suffer from floating point overflow, else will simply >> > push a trivial removal of the "1". >> >> 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. > > please post the patch
bench posted first to see if it is considered interesting enough. Bench over whole draw_mandelbrot using START/STOP timer on x86-64, Haswell, GNU/Linux, command line: ffmpeg -v error -f lavfi -i mandelbrot -f null - new (draw_mandelbrot): 2145115730 decicycles in draw_mandelbrot, 1 runs, 0 skips 1728922365 decicycles in draw_mandelbrot, 2 runs, 0 skips 1564209877 decicycles in draw_mandelbrot, 4 runs, 0 skips 1638069308 decicycles in draw_mandelbrot, 8 runs, 0 skips 1823837319 decicycles in draw_mandelbrot, 16 runs, 0 skips 2076266287 decicycles in draw_mandelbrot, 32 runs, 0 skips 2445350509 decicycles in draw_mandelbrot, 64 runs, 0 skips 3076303786 decicycles in draw_mandelbrot, 128 runs, 0 skips 3976923705 decicycles in draw_mandelbrot, 256 runs, 0 skips 7601861275 decicycles in draw_mandelbrot, 512 runs, 0 skips 20857881401 decicycles in draw_mandelbrot, 1024 runs, 0 skips old (draw_mandelbrot): 2134144710 decicycles in draw_mandelbrot, 1 runs, 0 skips 1801213045 decicycles in draw_mandelbrot, 2 runs, 0 skips 1632609867 decicycles in draw_mandelbrot, 4 runs, 0 skips 1668765306 decicycles in draw_mandelbrot, 8 runs, 0 skips 1845019538 decicycles in draw_mandelbrot, 16 runs, 0 skips 2064489945 decicycles in draw_mandelbrot, 32 runs, 0 skips 2485309937 decicycles in draw_mandelbrot, 64 runs, 0 skips 3149893392 decicycles in draw_mandelbrot, 128 runs, 0 skips 4048037523 decicycles in draw_mandelbrot, 256 runs, 0 skips 7954800255 decicycles in draw_mandelbrot, 512 runs, 0 skips 21393227201 decicycles in draw_mandelbrot, 1024 runs, 0 skips [...] _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
