mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-11-26 19:01:44 +02:00
101 lines
2.5 KiB
C
101 lines
2.5 KiB
C
/*
|
|
* Lagged Fibonacci PRNG
|
|
* Copyright (c) 2008 Michael Niedermayer
|
|
*
|
|
* This file is part of Libav.
|
|
*
|
|
* Libav 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.
|
|
*
|
|
* Libav 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 Libav; 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"
|
|
|
|
void av_cold 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;
|
|
|
|
av_lfg_init(&state, 42);
|
|
|
|
for (i = 0; i < 1000; i += 2) {
|
|
double bmg_out[2];
|
|
av_bmg_get(&state, bmg_out);
|
|
av_log(NULL, AV_LOG_INFO,
|
|
"%f\n%f\n",
|
|
bmg_out[0] * stddev + mean,
|
|
bmg_out[1] * stddev + mean);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif
|