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ffmpeg / libavutil / lfg.h @ 80a07f6e

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