On 3/11/2016 1:16 AM, Ganesh Ajjanagadde wrote:
> 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;
> + out[0] = ziggurat(lfg);
> + out[1] = ziggurat(lfg);
> }
>
> #ifdef TEST
> diff --git a/libavutil/lfg.h b/libavutil/lfg.h
> index ec90562..6241359 100644
> --- a/libavutil/lfg.h
> +++ b/libavutil/lfg.h
> @@ -52,7 +52,7 @@ static inline unsigned int av_mlfg_get(AVLFG *c){
> }
>
> /**
> - * Get the next two numbers generated by a Box-Muller Gaussian
> + * Get two numbers generated independently from a standard Gaussian
> distribution
I don't think a function called after Box-Muller Gaussian should suddenly
start using a different algorithm to generate random numbers.
How about adding a new av_ziggurat_get() or similarly named function for
this, and then replace av_bmg_get() usage where convenient?
> * generator using the random numbers issued by lfg.
> *
> * @param out array where the two generated numbers are placed
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