Edit File: lfg.h
/* * 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 */