Commit | Line | Data |
---|---|---|
2ba45a60 DM |
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 | typedef struct AVLFG { | |
26 | unsigned int state[64]; | |
27 | int index; | |
28 | } AVLFG; | |
29 | ||
30 | void av_lfg_init(AVLFG *c, unsigned int seed); | |
31 | ||
32 | /** | |
33 | * Get the next random unsigned 32-bit number using an ALFG. | |
34 | * | |
35 | * Please also consider a simple LCG like state= state*1664525+1013904223, | |
36 | * it may be good enough and faster for your specific use case. | |
37 | */ | |
38 | static inline unsigned int av_lfg_get(AVLFG *c){ | |
39 | c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; | |
40 | return c->state[c->index++ & 63]; | |
41 | } | |
42 | ||
43 | /** | |
44 | * Get the next random unsigned 32-bit number using a MLFG. | |
45 | * | |
46 | * Please also consider av_lfg_get() above, it is faster. | |
47 | */ | |
48 | static inline unsigned int av_mlfg_get(AVLFG *c){ | |
49 | unsigned int a= c->state[(c->index-55) & 63]; | |
50 | unsigned int b= c->state[(c->index-24) & 63]; | |
51 | return c->state[c->index++ & 63] = 2*a*b+a+b; | |
52 | } | |
53 | ||
54 | /** | |
55 | * Get the next two numbers generated by a Box-Muller Gaussian | |
56 | * generator using the random numbers issued by lfg. | |
57 | * | |
58 | * @param out array where the two generated numbers are placed | |
59 | */ | |
60 | void av_bmg_get(AVLFG *lfg, double out[2]); | |
61 | ||
62 | #endif /* AVUTIL_LFG_H */ |