Implement av_bmg_next(), a Box-Muller Gaussian random generator.

See the thread: "[FFmpeg-devel] [PATCH] Box-Muller gaussian generator". Originally committed as revision 20808 to svn://svn.ffmpeg.org/ffmpeg/trunk

Stefano Sabatini committed 16 years ago

Commit 3ba69a11 parent 62d75663 files · +43 −2Browse files

Unified · Split

3 files

@@ -35,8 +35,8 @@ · 34 unmodified lines
35	35	#define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
36	36
37	37	#define LIBAVUTIL_VERSION_MAJOR 50
38		−#define LIBAVUTIL_VERSION_MINOR 5
39		−#define LIBAVUTIL_VERSION_MICRO 1
	38	+#define LIBAVUTIL_VERSION_MINOR 6
	39	+#define LIBAVUTIL_VERSION_MICRO 0
40	40
41	41	#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
42	42	LIBAVUTIL_VERSION_MINOR, \

@@ -39,6 +39,21 @@ void av_cold av_lfg_init(AVLFG *c, unsigned int seed){ · 38 unmodified lines
39	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 = x1x1 + x2x2;
	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	57	#ifdef TEST
43	58	#include "log.h"
44	59	#include "common.h"
@@ -59,6 +74,24 @@ int main(void) · 14 unmodified lines
59	74	STOP_TIMER("624 calls of av_lfg_get");
60	75	}
61	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	95	return 0;
63	96	}
64	97	#endif

@@ -51,4 +51,12 @@ static inline unsigned int av_mlfg_get(AVLFG *c){ · 50 unmodified lines
51	51	return c->state[c->index++ & 63] = 2ab+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	62	#endif /* AVUTIL_LFG_H */

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