repositories / deb_ffmpeg.git / blame
| 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 */ |