lrintf is anyway used, suggesting we only care up to floating precision.
Rurthermore, there is a compat hack in avutil/libm for this function,
and it is used in avcodec/aacps_tablegen.h.
This yields a non-negligible speedup. Sample benchmark:
x86-64, Haswell, GNU/Linux:
old (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
new (draw_mandelbrot):
269882717 decicycles in draw_mandelbrot, 256 runs, 0 skips
296359285 decicycles in draw_mandelbrot, 512 runs, 0 skips
370076599 decicycles in draw_mandelbrot, 1024 runs, 0 skips
331478354 decicycles in draw_mandelbrot, 2048 runs, 0 skips
571904318 decicycles in draw_mandelbrot, 4096 runs, 0 skips
Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
---
libavfilter/vsrc_mandelbrot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libavfilter/vsrc_mandelbrot.c b/libavfilter/vsrc_mandelbrot.c
index 6ba8c59..6c210bb 100644
--- a/libavfilter/vsrc_mandelbrot.c
+++ b/libavfilter/vsrc_mandelbrot.c
@@ -334,11 +334,11 @@ static void draw_mandelbrot(AVFilterContext *ctx,
uint32_t *color, int linesize,
switch(s->outer){
case ITERATION_COUNT:
zr = i;
- c = lrintf((sin(zr)+1)*127) +
lrintf((sin(zr/1.234)+1)*127)*256*256 + lrintf((sin(zr/100)+1)*127)*256;
+ c = lrintf((sinf(zr)+1)*127) +
lrintf((sinf(zr/1.234)+1)*127)*256*256 + lrintf((sinf(zr/100)+1)*127)*256;
break;
case NORMALIZED_ITERATION_COUNT:
zr = i + log2(log(s->bailout) / log(zr*zr +
zi*zi));
- c = lrintf((sin(zr)+1)*127) +
lrintf((sin(zr/1.234)+1)*127)*256*256 + lrintf((sin(zr/100)+1)*127)*256;
+ c = lrintf((sinf(zr)+1)*127) +
lrintf((sinf(zr/1.234)+1)*127)*256*256 + lrintf((sinf(zr/100)+1)*127)*256;
break;
case WHITE:
c = 0xFFFFFF;
--
2.6.2
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