2 * Lagged Fibonacci PRNG
3 * Copyright (c) 2008 Michael Niedermayer
5 * This file is part of FFmpeg.
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.
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.
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
27 typedef struct AVLFG {
28 unsigned int state[64];
32 void av_lfg_init(AVLFG *c, unsigned int seed);
35 * Seed the state of the ALFG using binary data.
37 * Return value: 0 on success, negative value (AVERROR) on failure.
39 int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length);
42 * Get the next random unsigned 32-bit number using an ALFG.
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.
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];
53 * Get the next random unsigned 32-bit number using a MLFG.
55 * Please also consider av_lfg_get() above, it is faster.
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;
64 * Get the next two numbers generated by a Box-Muller Gaussian
65 * generator using the random numbers issued by lfg.
67 * @param out array where the two generated numbers are placed
69 void av_bmg_get(AVLFG *lfg, double out[2]);
71 #endif /* AVUTIL_LFG_H */