| /* | |
| * Lagged Fibonacci PRNG | |
| * Copyright (c) 2008 Michael Niedermayer | |
| * | |
| * This file is part of FFmpeg. | |
| * | |
| * FFmpeg is free software; you can redistribute it and/or | |
| * modify it under the terms of the GNU Lesser General Public | |
| * License as published by the Free Software Foundation; either | |
| * version 2.1 of the License, or (at your option) any later version. | |
| * | |
| * FFmpeg is distributed in the hope that it will be useful, | |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| * Lesser General Public License for more details. | |
| * | |
| * You should have received a copy of the GNU Lesser General Public | |
| * License along with FFmpeg; if not, write to the Free Software | |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
| */ | |
| /** | |
| * Context structure for the Lagged Fibonacci PRNG. | |
| * The exact layout, types and content of this struct may change and should | |
| * not be accessed directly. Only its `sizeof()` is guaranteed to stay the same | |
| * to allow easy instanciation. | |
| */ | |
| typedef struct AVLFG { | |
| unsigned int state[64]; | |
| int index; | |
| } AVLFG; | |
| void av_lfg_init(AVLFG *c, unsigned int seed); | |
| /** | |
| * Seed the state of the ALFG using binary data. | |
| * | |
| * @return 0 on success, negative value (AVERROR) on failure. | |
| */ | |
| int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length); | |
| /** | |
| * Get the next random unsigned 32-bit number using an ALFG. | |
| * | |
| * Please also consider a simple LCG like state= state*1664525+1013904223, | |
| * it may be good enough and faster for your specific use case. | |
| */ | |
| static inline unsigned int av_lfg_get(AVLFG *c){ | |
| unsigned a = c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; | |
| c->index += 1U; | |
| return a; | |
| } | |
| /** | |
| * Get the next random unsigned 32-bit number using a MLFG. | |
| * | |
| * Please also consider 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]; | |
| a = c->state[c->index & 63] = 2*a*b+a+b; | |
| c->index += 1U; | |
| return a; | |
| } | |
| /** | |
| * Get the next two numbers generated by a Box-Muller Gaussian | |
| * generator using the random numbers issued by lfg. | |
| * | |
| * @param lfg pointer to the contex structure | |
| * @param out array where the two generated numbers are placed | |
| */ | |
| void av_bmg_get(AVLFG *lfg, double out[2]); | |