Code clean-up for crc.c, lfg.c, log.c, random_see.d, rational.c and tree.c.
[libav.git] / libavutil / lfg.c
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1/*
2 * Lagged Fibonacci PRNG
3 * Copyright (c) 2008 Michael Niedermayer
4 *
2912e87a 5 * This file is part of Libav.
2754fe8b 6 *
2912e87a 7 * Libav is free software; you can redistribute it and/or
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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 *
2912e87a 12 * Libav is distributed in the hope that it will be useful,
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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
2912e87a 18 * License along with Libav; if not, write to the Free Software
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19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include <inttypes.h>
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23#include <limits.h>
24#include <math.h>
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25#include "lfg.h"
26#include "md5.h"
27#include "intreadwrite.h"
2ed6f399 28#include "attributes.h"
2754fe8b 29
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30void av_cold av_lfg_init(AVLFG *c, unsigned int seed)
31{
32 uint8_t tmp[16] = { 0 };
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33 int i;
34
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35 for (i = 8; i < 64; i += 4) {
36 AV_WL32(tmp, seed);
37 tmp[4] = i;
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);
2754fe8b 43 }
425b45d4 44 c->index = 0;
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45}
46
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47void av_bmg_get(AVLFG *lfg, double out[2])
48{
49 double x1, x2, w;
50
51 do {
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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;
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55 } while (w >= 1.0);
56
57 w = sqrt((-2.0 * log(w)) / w);
58 out[0] = x1 * w;
59 out[1] = x2 * w;
60}
61
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62#ifdef TEST
63#include "log.h"
2ed6f399 64#include "timer.h"
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65
66int main(void)
67{
425b45d4 68 int x = 0;
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69 int i, j;
70 AVLFG state;
71
72 av_lfg_init(&state, 0xdeadbeef);
73 for (j = 0; j < 10000; j++) {
74 START_TIMER
75 for (i = 0; i < 624; i++) {
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76 //av_log(NULL, AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
77 x += av_lfg_get(&state);
2754fe8b 78 }
0e4cb6cb 79 STOP_TIMER("624 calls of av_lfg_get");
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80 }
81 av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
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82
83 /* BMG usage example */
84 {
85 double mean = 1000;
86 double stddev = 53;
87
88 av_lfg_init(&state, 42);
89
90 for (i = 0; i < 1000; i += 2) {
91 double bmg_out[2];
92 av_bmg_get(&state, bmg_out);
93 av_log(NULL, AV_LOG_INFO,
94 "%f\n%f\n",
95 bmg_out[0] * stddev + mean,
96 bmg_out[1] * stddev + mean);
97 }
98 }
99
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100 return 0;
101}
102#endif