From 310d442456881e448d22afa9d8b1a8687b5dd2bf Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Wed, 30 Jul 2008 23:08:07 +0000 Subject: 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 --- libavutil/lfg.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'libavutil/lfg.h') 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 -- cgit v1.2.3