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
25 #include "intreadwrite.h"
26 #include "attributes.h"
28 void av_cold av_lfg_init(AVLFG *c, unsigned int seed){
33 AV_WL32(tmp, seed); tmp[4]=i;
34 av_md5_sum(tmp, tmp, 16);
35 c->state[i ]= AV_RL32(tmp);
36 c->state[i+1]= AV_RL32(tmp+4);
37 c->state[i+2]= AV_RL32(tmp+8);
38 c->state[i+3]= AV_RL32(tmp+12);
43 void av_bmg_get(AVLFG *lfg, double out[2])
48 x1 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
49 x2 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
53 w = sqrt((-2.0 * log(w)) / w);
68 av_lfg_init(&state, 0xdeadbeef);
69 for (j = 0; j < 10000; j++) {
71 for (i = 0; i < 624; i++) {
72 // av_log(NULL,AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
73 x+=av_lfg_get(&state);
75 STOP_TIMER("624 calls of av_lfg_get");
77 av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
79 /* BMG usage example */
84 av_lfg_init(&state, 42);
86 for (i = 0; i < 1000; i += 2) {
88 av_bmg_get(&state, bmg_out);
89 av_log(NULL, AV_LOG_INFO,
91 bmg_out[0] * stddev + mean,
92 bmg_out[1] * stddev + mean);