| /* |
| * 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 |
| */ |
| |
| #ifndef AVUTIL_LFG_H |
| #define AVUTIL_LFG_H |
| |
| typedef struct AVLFG { |
| unsigned int state[64]; |
| int index; |
| } AVLFG; |
| |
| void av_lfg_init(AVLFG *c, unsigned int seed); |
| |
| /** |
| * 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){ |
| c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; |
| return c->state[c->index++ & 63]; |
| } |
| |
| /** |
| * 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]; |
| return c->state[c->index++ & 63] = 2*a*b+a+b; |
| } |
| |
| /** |
| * Get the next two numbers generated by a Box-Muller Gaussian |
| * generator using the random numbers issued by lfg. |
| * |
| * @param out array where the two generated numbers are placed |
| */ |
| void av_bmg_get(AVLFG *lfg, double out[2]); |
| |
| #endif /* AVUTIL_LFG_H */ |