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69 lines
2.4 KiB
69 lines
2.4 KiB
/* |
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* Mersenne Twister Random Algorithm |
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* Copyright (c) 2006 Ryan Martell. |
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* Based on A C-program for MT19937, with initialization improved 2002/1/26. Coded by |
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* Takuji Nishimura and Makoto Matsumoto. |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#ifndef FFMPEG_RANDOM_H |
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#define FFMPEG_RANDOM_H |
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#define AV_RANDOM_N 624 |
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typedef struct { |
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unsigned int mt[AV_RANDOM_N]; ///< the array for the state vector |
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int index; ///< current untempered value we use as the base. |
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} AVRandomState; |
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void av_init_random(unsigned int seed, AVRandomState *state); ///< to be inlined, the struct must be visible, so it doesn't make sense to try and keep it opaque with malloc/free like calls |
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void av_random_generate_untempered_numbers(AVRandomState *state); ///< Regenerate the untempered numbers (must be done every 624 iterations, or it will loop) |
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/** generates a random number on [0,0xffffffff]-interval */ |
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static inline unsigned int av_random(AVRandomState *state) |
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{ |
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unsigned int y; |
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// regenerate the untempered numbers if we should... |
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if (state->index >= AV_RANDOM_N) |
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av_random_generate_untempered_numbers(state); |
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// grab one... |
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y = state->mt[state->index++]; |
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/* Now temper (Mersenne Twister coefficients) The coefficients for MT19937 are.. */ |
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y ^= (y >> 11); |
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y ^= (y << 7) & 0x9d2c5680; |
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y ^= (y << 15) & 0xefc60000; |
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y ^= (y >> 18); |
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return y; |
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} |
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/** return random in range [0-1] as double */ |
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static inline double av_random_real1(AVRandomState *state) |
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{ |
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/* divided by 2^32-1 */ |
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return av_random(state) * (1.0 / 4294967296.0); |
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} |
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// only available if DEBUG is defined in the .c file |
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void av_benchmark_random(void); |
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#endif /* FFMPEG_RANDOM_H */
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