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.
79 lines
2.7 KiB
79 lines
2.7 KiB
/* |
|
* Mersenne Twister Random Algorithm |
|
* Copyright (c) 2006 Ryan Martell |
|
* Based on A C-program for MT19937, with initialization improved 2002/1/26. Coded by |
|
* Takuji Nishimura and Makoto Matsumoto. |
|
* |
|
* 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 |
|
*/ |
|
|
|
#ifndef AVUTIL_RANDOM_H |
|
#define AVUTIL_RANDOM_H |
|
|
|
#define AV_RANDOM_N 624 |
|
|
|
#include "avutil.h" |
|
#include "common.h" |
|
|
|
typedef struct { |
|
unsigned int mt[AV_RANDOM_N]; ///< the array for the state vector |
|
int index; ///< Current untempered value we use as the base. |
|
} AVRandomState; |
|
|
|
|
|
#if LIBAVUTIL_VERSION_MAJOR < 50 |
|
attribute_deprecated void av_init_random(unsigned int seed, AVRandomState *state); |
|
#endif |
|
void av_random_init(AVRandomState *state, unsigned int seed); ///< To be inlined, the struct must be visible. So it does not make sense to try and keep it opaque with malloc/free-like calls. |
|
void av_random_generate_untempered_numbers(AVRandomState *state); ///< Regenerate the untempered numbers (must be done every 624 iterations, or it will loop). |
|
|
|
/** |
|
* Generates a random number from the interval [0,0xffffffff]. |
|
* |
|
* Please do NOT use the Mersenne Twister, it is slow. Use the random generator |
|
* from lfg.c/h or a simple LCG like state= state*1664525+1013904223. |
|
* If you still choose to use MT, expect that you will have to provide |
|
* some evidence that it makes a difference for the case where you use it. |
|
*/ |
|
static inline unsigned int av_random(AVRandomState *state) |
|
{ |
|
unsigned int y; |
|
|
|
// Regenerate the untempered numbers if we should... |
|
if (state->index >= AV_RANDOM_N) |
|
av_random_generate_untempered_numbers(state); |
|
|
|
// Grab one... |
|
y = state->mt[state->index++]; |
|
|
|
/* Now temper (Mersenne Twister coefficients). The coefficients for MT19937 are.. */ |
|
y ^= (y >> 11); |
|
y ^= (y << 7) & 0x9d2c5680; |
|
y ^= (y << 15) & 0xefc60000; |
|
y ^= (y >> 18); |
|
|
|
return y; |
|
} |
|
|
|
/** Return random in range [0-1] as double. */ |
|
static inline double av_random_real1(AVRandomState *state) |
|
{ |
|
/* divided by 2^32-1 */ |
|
return av_random(state) * (1.0 / 4294967296.0); |
|
} |
|
|
|
#endif /* AVUTIL_RANDOM_H */
|
|
|