diff options
| author | Ganesh Ajjanagadde <gajjanagadde@gmail.com> | 2015-11-22 11:49:15 -0500 |
|---|---|---|
| committer | Ganesh Ajjanagadde <gajjanagadde@gmail.com> | 2015-11-24 20:36:40 -0500 |
| commit | e9c7493f19a610f44690ef2f2f3737a3c6236fdf (patch) | |
| tree | 64790256125382c669950ffa20650bb905f70fcd /libavfilter/vsrc_mandelbrot.c | |
| parent | 81a0aec29e7aa325b46b1942fe477b83fb54eb3a (diff) | |
avfilter/vsrc_mandelbrot: avoid sqrt for epsilon calculation
This rewrites into a similar expression avoiding sqrt. Similarity is
assured since sqrt(x^2 + y^2)/(x+y) lies in [1/sqrt(2), 1] for x, y > 0.
Tested on x86-64, Haswell, GNU/Linux.
Command:
ffmpeg -f lavfi -i mandelbrot -f null -
old (draw_mandelbrot):
277625266 decicycles in draw_mandelbrot, 256 runs, 0 skips
304527322 decicycles in draw_mandelbrot, 512 runs, 0 skips
377593582 decicycles in draw_mandelbrot, 1024 runs, 0 skips
338539499 decicycles in draw_mandelbrot, 2048 runs, 0 skips
583630357 decicycles in draw_mandelbrot, 4096 runs, 0 skips
new (draw_mandelbrot):
274635709 decicycles in draw_mandelbrot, 256 runs, 0 skips
300287046 decicycles in draw_mandelbrot, 512 runs, 0 skips
371819935 decicycles in draw_mandelbrot, 1024 runs, 0 skips
336663765 decicycles in draw_mandelbrot, 2048 runs, 0 skips
581851016 decicycles in draw_mandelbrot, 4096 runs, 0 skips
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Diffstat (limited to 'libavfilter/vsrc_mandelbrot.c')
| -rw-r--r-- | libavfilter/vsrc_mandelbrot.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/libavfilter/vsrc_mandelbrot.c b/libavfilter/vsrc_mandelbrot.c index c79ea2e39a..91bf63fd42 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*(abs(x-s->w/2) + abs(y-s->h/2))/s->w; #define Z_Z2_C(outr,outi,inr,ini)\ outr= inr*inr - ini*ini + cr;\ |