See the thread: "[FFmpeg-devel] [PATCH] Box-Muller gaussian generator". Originally committed as revision 20808 to svn://svn.ffmpeg.org/ffmpeg/trunk
Unified · Split
| @@ -35,8 +35,8 @@ · 34 unmodified lines | |||
| 35 | #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c) | 35 | #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c) |
| 36 | 36 | ||
| 37 | #define LIBAVUTIL_VERSION_MAJOR 50 | 37 | #define LIBAVUTIL_VERSION_MAJOR 50 |
| 38 | #define LIBAVUTIL_VERSION_MINOR 5 | 38 | #define LIBAVUTIL_VERSION_MINOR 6 |
| 39 | #define LIBAVUTIL_VERSION_MICRO 1 | 39 | #define LIBAVUTIL_VERSION_MICRO 0 |
| 40 | 40 | ||
| 41 | #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \ | 41 | #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \ |
| 42 | LIBAVUTIL_VERSION_MINOR, \ | 42 | LIBAVUTIL_VERSION_MINOR, \ |
| @@ -39,6 +39,21 @@ void av_cold av_lfg_init(AVLFG *c, unsigned int seed){ · 38 unmodified lines | |||
| 39 | c->index=0; | 39 | c->index=0; |
| 40 | } | 40 | } |
| 41 | 41 | ||
| 42 | void av_bmg_get(AVLFG *lfg, double out[2]) | ||
| 43 | { | ||
| 44 | double x1, x2, w; | ||
| 45 | |||
| 46 | do { | ||
| 47 | x1 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0; | ||
| 48 | x2 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0; | ||
| 49 | w = x1*x1 + x2*x2; | ||
| 50 | } while (w >= 1.0); | ||
| 51 | |||
| 52 | w = sqrt((-2.0 * log(w)) / w); | ||
| 53 | out[0] = x1 * w; | ||
| 54 | out[1] = x2 * w; | ||
| 55 | } | ||
| 56 | |||
| 42 | #ifdef TEST | 57 | #ifdef TEST |
| 43 | #include "log.h" | 58 | #include "log.h" |
| 44 | #include "common.h" | 59 | #include "common.h" |
| @@ -59,6 +74,24 @@ int main(void) · 14 unmodified lines | |||
| 59 | STOP_TIMER("624 calls of av_lfg_get"); | 74 | STOP_TIMER("624 calls of av_lfg_get"); |
| 60 | } | 75 | } |
| 61 | av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x); | 76 | av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x); |
| 77 | |||
| 78 | /* BMG usage example */ | ||
| 79 | { | ||
| 80 | double mean = 1000; | ||
| 81 | double stddev = 53; | ||
| 82 | |||
| 83 | av_lfg_init(&state, 42); | ||
| 84 | |||
| 85 | for (i = 0; i < 1000; i += 2) { | ||
| 86 | double bmg_out[2]; | ||
| 87 | av_bmg_get(&state, bmg_out); | ||
| 88 | av_log(NULL, AV_LOG_INFO, | ||
| 89 | "%f\n%f\n", | ||
| 90 | bmg_out[0] * stddev + mean, | ||
| 91 | bmg_out[1] * stddev + mean); | ||
| 92 | } | ||
| 93 | } | ||
| 94 | |||
| 62 | return 0; | 95 | return 0; |
| 63 | } | 96 | } |
| 64 | #endif | 97 | #endif |
| @@ -51,4 +51,12 @@ static inline unsigned int av_mlfg_get(AVLFG *c){ · 50 unmodified lines | |||
| 51 | return c->state[c->index++ & 63] = 2*a*b+a+b; | 51 | return c->state[c->index++ & 63] = 2*a*b+a+b; |
| 52 | } | 52 | } |
| 53 | 53 | ||
| 54 | /** | ||
| 55 | * Gets the next two numbers generated by a Box-Muller Gaussian | ||
| 56 | * generator using the random numbers issued by lfg. | ||
| 57 | * | ||
| 58 | * @param out[2] array where are placed the two generated numbers | ||
| 59 | */ | ||
| 60 | void av_bmg_get(AVLFG *lfg, double out[2]); | ||
| 61 | |||
| 54 | #endif /* AVUTIL_LFG_H */ | 62 | #endif /* AVUTIL_LFG_H */ |