mirror of https://github.com/FFmpeg/FFmpeg.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
118 lines
3.3 KiB
118 lines
3.3 KiB
/* |
|
* Lagged Fibonacci PRNG |
|
* Copyright (c) 2008 Michael Niedermayer |
|
* |
|
* This file is part of FFmpeg. |
|
* |
|
* FFmpeg is free software; you can redistribute it and/or |
|
* modify it under the terms of the GNU Lesser General Public |
|
* License as published by the Free Software Foundation; either |
|
* version 2.1 of the License, or (at your option) any later version. |
|
* |
|
* FFmpeg is distributed in the hope that it will be useful, |
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of |
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
|
* Lesser General Public License for more details. |
|
* |
|
* You should have received a copy of the GNU Lesser General Public |
|
* License along with FFmpeg; if not, write to the Free Software |
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
|
*/ |
|
|
|
#include <inttypes.h> |
|
#include <limits.h> |
|
#include <math.h> |
|
#include "lfg.h" |
|
#include "md5.h" |
|
#include "intreadwrite.h" |
|
#include "attributes.h" |
|
|
|
av_cold void av_lfg_init(AVLFG *c, unsigned int seed) |
|
{ |
|
uint8_t tmp[16] = { 0 }; |
|
int i; |
|
|
|
for (i = 8; i < 64; i += 4) { |
|
AV_WL32(tmp, seed); |
|
tmp[4] = i; |
|
av_md5_sum(tmp, tmp, 16); |
|
c->state[i ] = AV_RL32(tmp); |
|
c->state[i + 1] = AV_RL32(tmp + 4); |
|
c->state[i + 2] = AV_RL32(tmp + 8); |
|
c->state[i + 3] = AV_RL32(tmp + 12); |
|
} |
|
c->index = 0; |
|
} |
|
|
|
void av_bmg_get(AVLFG *lfg, double out[2]) |
|
{ |
|
double x1, x2, w; |
|
|
|
do { |
|
x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
|
x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
|
w = x1 * x1 + x2 * x2; |
|
} while (w >= 1.0); |
|
|
|
w = sqrt((-2.0 * log(w)) / w); |
|
out[0] = x1 * w; |
|
out[1] = x2 * w; |
|
} |
|
|
|
#ifdef TEST |
|
#include "log.h" |
|
#include "timer.h" |
|
|
|
int main(void) |
|
{ |
|
int x = 0; |
|
int i, j; |
|
AVLFG state; |
|
|
|
av_lfg_init(&state, 0xdeadbeef); |
|
for (j = 0; j < 10000; j++) { |
|
START_TIMER |
|
for (i = 0; i < 624; i++) { |
|
//av_log(NULL, AV_LOG_ERROR, "%X\n", av_lfg_get(&state)); |
|
x += av_lfg_get(&state); |
|
} |
|
STOP_TIMER("624 calls of av_lfg_get"); |
|
} |
|
av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x); |
|
|
|
/* BMG usage example */ |
|
{ |
|
double mean = 1000; |
|
double stddev = 53; |
|
double samp_mean = 0.0, samp_stddev = 0.0; |
|
double samp0, samp1; |
|
|
|
av_lfg_init(&state, 42); |
|
|
|
for (i = 0; i < 1000; i += 2) { |
|
double bmg_out[2]; |
|
av_bmg_get(&state, bmg_out); |
|
samp0 = bmg_out[0] * stddev + mean; |
|
samp1 = bmg_out[1] * stddev + mean; |
|
samp_mean += samp0 + samp1; |
|
samp_stddev += samp0 * samp0 + samp1 * samp1; |
|
av_log(NULL, AV_LOG_INFO, |
|
"%f\n%f\n", |
|
samp0, |
|
samp1); |
|
} |
|
/* TODO: add proper normality test */ |
|
samp_mean /= 1000; |
|
samp_stddev /= 999; |
|
samp_stddev -= (1000.0/999.0)*samp_mean*samp_mean; |
|
samp_stddev = sqrt(samp_stddev); |
|
av_log(NULL, AV_LOG_INFO, "sample mean : %f\n" |
|
"true mean : %f\n" |
|
"sample stddev: %f\n" |
|
"true stddev : %f\n", |
|
samp_mean, mean, samp_stddev, stddev); |
|
} |
|
|
|
return 0; |
|
} |
|
#endif
|
|
|