2 * Lagged Fibonacci PRNG
3 * Copyright (c) 2008 Michael Niedermayer
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
27 #include "intreadwrite.h"
28 #include "attributes.h"
30 av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
32 uint8_t tmp[16] = { 0 };
35 for (i = 8; i < 64; i += 4) {
38 av_md5_sum(tmp, tmp, 16);
39 c->state[i ] = AV_RL32(tmp);
40 c->state[i + 1] = AV_RL32(tmp + 4);
41 c->state[i + 2] = AV_RL32(tmp + 8);
42 c->state[i + 3] = AV_RL32(tmp + 12);
47 void av_bmg_get(AVLFG *lfg, double out[2])
52 x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
53 x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
54 w = x1 * x1 + x2 * x2;
57 w = sqrt((-2.0 * log(w)) / w);