[SCM] libav/experimental: Add a multiplicative LFG for those thinking the additive is not good enough, just 4 lines of code.

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit 310d442456881e448d22afa9d8b1a8687b5dd2bf
Author: Michael Niedermayer <michaelni at gmx.at>
Date:   Wed Jul 30 23:08:07 2008 +0000

    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

diff --git a/libavutil/lfg.h b/libavutil/lfg.h
index 36c36f4..3d3f933 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

-- 
Libav/FFmpeg packaging