yading@11: /*
yading@11:  * Lagged Fibonacci PRNG
yading@11:  * Copyright (c) 2008 Michael Niedermayer
yading@11:  *
yading@11:  * This file is part of FFmpeg.
yading@11:  *
yading@11:  * FFmpeg is free software; you can redistribute it and/or
yading@11:  * modify it under the terms of the GNU Lesser General Public
yading@11:  * License as published by the Free Software Foundation; either
yading@11:  * version 2.1 of the License, or (at your option) any later version.
yading@11:  *
yading@11:  * FFmpeg is distributed in the hope that it will be useful,
yading@11:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@11:  * Lesser General Public License for more details.
yading@11:  *
yading@11:  * You should have received a copy of the GNU Lesser General Public
yading@11:  * License along with FFmpeg; if not, write to the Free Software
yading@11:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@11:  */
yading@11: 
yading@11: #ifndef AVUTIL_LFG_H
yading@11: #define AVUTIL_LFG_H
yading@11: 
yading@11: typedef struct AVLFG {
yading@11:     unsigned int state[64];
yading@11:     int index;
yading@11: } AVLFG;
yading@11: 
yading@11: void av_lfg_init(AVLFG *c, unsigned int seed);
yading@11: 
yading@11: /**
yading@11:  * Get the next random unsigned 32-bit number using an ALFG.
yading@11:  *
yading@11:  * Please also consider a simple LCG like state= state*1664525+1013904223,
yading@11:  * it may be good enough and faster for your specific use case.
yading@11:  */
yading@11: static inline unsigned int av_lfg_get(AVLFG *c){
yading@11:     c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
yading@11:     return c->state[c->index++ & 63];
yading@11: }
yading@11: 
yading@11: /**
yading@11:  * Get the next random unsigned 32-bit number using a MLFG.
yading@11:  *
yading@11:  * Please also consider av_lfg_get() above, it is faster.
yading@11:  */
yading@11: static inline unsigned int av_mlfg_get(AVLFG *c){
yading@11:     unsigned int a= c->state[(c->index-55) & 63];
yading@11:     unsigned int b= c->state[(c->index-24) & 63];
yading@11:     return c->state[c->index++ & 63] = 2*a*b+a+b;
yading@11: }
yading@11: 
yading@11: /**
yading@11:  * Get the next two numbers generated by a Box-Muller Gaussian
yading@11:  * generator using the random numbers issued by lfg.
yading@11:  *
yading@11:  * @param out array where the two generated numbers are placed
yading@11:  */
yading@11: void av_bmg_get(AVLFG *lfg, double out[2]);
yading@11: 
yading@11: #endif /* AVUTIL_LFG_H */