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| author | Michael Niedermayer <michaelni@gmx.at> | 2008-07-30 23:08:07 +0000 |
|---|---|---|
| committer | Michael Niedermayer <michaelni@gmx.at> | 2008-07-30 23:08:07 +0000 |
| commit | 310d442456881e448d22afa9d8b1a8687b5dd2bf (patch) | |
| tree | 9ef4880d45f038a1d1a9909d7dbd093b86c634bb | |
| parent | 62f2523062c022c511eccff88a0dc2cf9e62a70a (diff) | |
| download | ffmpeg-310d442456881e448d22afa9d8b1a8687b5dd2bf.tar.gz | |
Add a multiplicative LFG for those thinking the additive is not good
enough, just 4 lines of code.
Originally committed as revision 14478 to svn://svn.ffmpeg.org/ffmpeg/trunk
| -rw-r--r-- | libavutil/lfg.h | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/libavutil/lfg.h b/libavutil/lfg.h index 36c36f446b..3d3f9332ab 100644 --- a/libavutil/lfg.h +++ b/libavutil/lfg.h @@ -30,7 +30,7 @@ typedef struct { void av_lfg_init(AVLFG *c, unsigned int seed); /** - * Gets the next random unsigned 32bit number. + * Gets the next random unsigned 32bit number using a ALFG. * * Please also consider a simple LCG like state= state*1664525+1013904223, * it may be good enough and faster for your specific use case. @@ -40,4 +40,15 @@ static inline unsigned int av_lfg_get(AVLFG *c){ return c->state[c->index++ & 63]; } +/** + * Gets the next random unsigned 32bit number using a MLFG. + * + * Please also consider the av_lfg_get() above, it is faster. + */ +static inline unsigned int av_mlfg_get(AVLFG *c){ + unsigned int a= c->state[(c->index-55) & 63]; + unsigned int b= c->state[(c->index-24) & 63]; + return c->state[c->index++ & 63] = a*b+a+b; +} + #endif //FFMPEG_LFG_H |