Replace many includes of libavutil/common.h with what is actually needed
[libav.git] / libavutil / lfg.c
1 /*
2 * Lagged Fibonacci PRNG
3 * Copyright (c) 2008 Michael Niedermayer
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22 #include <inttypes.h>
23 #include "lfg.h"
24 #include "md5.h"
25 #include "intreadwrite.h"
26 #include "attributes.h"
27
28 void av_cold av_lfg_init(AVLFG *c, unsigned int seed){
29 uint8_t tmp[16]={0};
30 int i;
31
32 for(i=8; i<64; i+=4){
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);
39 }
40 c->index=0;
41 }
42
43 void av_bmg_get(AVLFG *lfg, double out[2])
44 {
45 double x1, x2, w;
46
47 do {
48 x1 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
49 x2 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
50 w = x1*x1 + x2*x2;
51 } while (w >= 1.0);
52
53 w = sqrt((-2.0 * log(w)) / w);
54 out[0] = x1 * w;
55 out[1] = x2 * w;
56 }
57
58 #ifdef TEST
59 #include "log.h"
60 #include "timer.h"
61
62 int main(void)
63 {
64 int x=0;
65 int i, j;
66 AVLFG state;
67
68 av_lfg_init(&state, 0xdeadbeef);
69 for (j = 0; j < 10000; j++) {
70 START_TIMER
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);
74 }
75 STOP_TIMER("624 calls of av_lfg_get");
76 }
77 av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
78
79 /* BMG usage example */
80 {
81 double mean = 1000;
82 double stddev = 53;
83
84 av_lfg_init(&state, 42);
85
86 for (i = 0; i < 1000; i += 2) {
87 double bmg_out[2];
88 av_bmg_get(&state, bmg_out);
89 av_log(NULL, AV_LOG_INFO,
90 "%f\n%f\n",
91 bmg_out[0] * stddev + mean,
92 bmg_out[1] * stddev + mean);
93 }
94 }
95
96 return 0;
97 }
98 #endif