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lfg.h
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1 /*
2  * Lagged Fibonacci PRNG
3  * Copyright (c) 2008 Michael Niedermayer
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVUTIL_LFG_H
23 #define AVUTIL_LFG_H
24 
25 #include <stdint.h>
26 
27 typedef struct AVLFG {
28  unsigned int state[64];
29  int index;
30 } AVLFG;
31 
32 void av_lfg_init(AVLFG *c, unsigned int seed);
33 
34 /**
35  * Seed the state of the ALFG using binary data.
36  *
37  * Return value: 0 on success, negative value (AVERROR) on failure.
38  */
39 int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length);
40 
41 /**
42  * Get the next random unsigned 32-bit number using an ALFG.
43  *
44  * Please also consider a simple LCG like state= state*1664525+1013904223,
45  * it may be good enough and faster for your specific use case.
46  */
47 static inline unsigned int av_lfg_get(AVLFG *c){
48  c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
49  return c->state[c->index++ & 63];
50 }
51 
52 /**
53  * Get the next random unsigned 32-bit number using a MLFG.
54  *
55  * Please also consider av_lfg_get() above, it is faster.
56  */
57 static inline unsigned int av_mlfg_get(AVLFG *c){
58  unsigned int a= c->state[(c->index-55) & 63];
59  unsigned int b= c->state[(c->index-24) & 63];
60  return c->state[c->index++ & 63] = 2*a*b+a+b;
61 }
62 
63 /**
64  * Get the next two numbers generated by a Box-Muller Gaussian
65  * generator using the random numbers issued by lfg.
66  *
67  * @param out array where the two generated numbers are placed
68  */
69 void av_bmg_get(AVLFG *lfg, double out[2]);
70 
71 #endif /* AVUTIL_LFG_H */
Definition: lfg.h:27
void av_lfg_init(AVLFG *c, unsigned int seed)
Definition: lfg.c:32
int index
Definition: lfg.h:29
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:101
const char * b
Definition: vf_curves.c:113
uint8_t
static unsigned int av_mlfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using a MLFG.
Definition: lfg.h:57
GLsizei GLsizei * length
Definition: opengl_enc.c:115
int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length)
Seed the state of the ALFG using binary data.
Definition: lfg.c:64
static unsigned int seed
Definition: videogen.c:78
static unsigned int av_lfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using an ALFG.
Definition: lfg.h:47
void av_bmg_get(AVLFG *lfg, double out[2])
Get the next two numbers generated by a Box-Muller Gaussian generator using the random numbers issued...
Definition: lfg.c:49
unsigned int state[64]
Definition: lfg.h:28
static double c[64]
FILE * out
Definition: movenc.c:54