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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* |
| 2 | * Lagged Fibonacci PRNG |
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| 3 | * Copyright (c) 2008 Michael Niedermayer |
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| 4 | * |
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| 5 | * This file is part of FFmpeg. |
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| 6 | * |
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| 7 | * FFmpeg 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 |
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| 9 | * License as published by the Free Software Foundation; either |
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| 10 | * version 2.1 of the License, or (at your option) any later version. |
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| 11 | * |
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| 12 | * FFmpeg 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 |
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 15 | * Lesser General Public License for more details. |
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| 16 | * |
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| 17 | * You should have received a copy of the GNU Lesser General Public |
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| 18 | * License along with FFmpeg; if not, write to the Free Software |
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| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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| 20 | */ |
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| 21 | |||
| 22 | #include |
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| 23 | #include |
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| 24 | #include |
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| 25 | #include "lfg.h" |
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| 26 | #include "md5.h" |
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| 27 | #include "intreadwrite.h" |
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| 28 | #include "attributes.h" |
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| 29 | |||
| 30 | av_cold void av_lfg_init(AVLFG *c, unsigned int seed) |
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| 31 | { |
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| 32 | uint8_t tmp[16] = { 0 }; |
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| 33 | int i; |
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| 34 | |||
| 35 | for (i = 8; i < 64; i += 4) { |
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| 36 | AV_WL32(tmp, seed); |
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| 37 | tmp[4] = i; |
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| 38 | av_md5_sum(tmp, tmp, 16); |
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| 39 | c->state[i ] = AV_RL32(tmp); |
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| 40 | c->state[i + 1] = AV_RL32(tmp + 4); |
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| 41 | c->state[i + 2] = AV_RL32(tmp + 8); |
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| 42 | c->state[i + 3] = AV_RL32(tmp + 12); |
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| 43 | } |
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| 44 | c->index = 0; |
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| 45 | } |
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| 46 | |||
| 47 | void av_bmg_get(AVLFG *lfg, double out[2]) |
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| 48 | { |
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| 49 | double x1, x2, w; |
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| 50 | |||
| 51 | do { |
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| 52 | x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
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| 53 | x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
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| 54 | w = x1 * x1 + x2 * x2; |
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| 55 | } while (w >= 1.0); |
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| 56 | |||
| 57 | w = sqrt((-2.0 * log(w)) / w); |
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| 58 | out[0] = x1 * w; |
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| 59 | out[1] = x2 * w; |
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| 60 | } |
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| 61 | |||
| 62 | #ifdef TEST |
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| 63 | #include "log.h" |
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| 64 | #include "timer.h" |
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| 65 | |||
| 66 | int main(void) |
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| 67 | { |
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| 68 | int x = 0; |
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| 69 | int i, j; |
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| 70 | AVLFG state; |
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| 71 | |||
| 72 | av_lfg_init(&state, 0xdeadbeef); |
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| 73 | for (j = 0; j < 10000; j++) { |
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| 74 | START_TIMER |
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| 75 | for (i = 0; i < 624; i++) { |
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| 76 | //av_log(NULL, AV_LOG_ERROR, "%X\n", av_lfg_get(&state)); |
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| 77 | x += av_lfg_get(&state); |
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| 78 | } |
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| 79 | STOP_TIMER("624 calls of av_lfg_get"); |
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| 80 | } |
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| 81 | av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x); |
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| 82 | |||
| 83 | /* BMG usage example */ |
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| 84 | { |
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| 85 | double mean = 1000; |
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| 86 | double stddev = 53; |
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| 87 | |||
| 88 | av_lfg_init(&state, 42); |
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| 89 | |||
| 90 | for (i = 0; i < 1000; i += 2) { |
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| 91 | double bmg_out[2]; |
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| 92 | av_bmg_get(&state, bmg_out); |
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| 93 | av_log(NULL, AV_LOG_INFO, |
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| 94 | "%f\n%f\n", |
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| 95 | bmg_out[0] * stddev + mean, |
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| 96 | bmg_out[1] * stddev + mean); |
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| 97 | } |
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| 98 | } |
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| 99 | |||
| 100 | return 0; |
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| 101 | } |
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| 102 | #endif |