[hts-users:01761] Re: bug fix in HGen.c for random parameter generation

[Keiichi Tokuda <tokuda@xxxxxxxxxxxx>]

Thank you very much for reporting it.  You are right.
We will reflect this in the future release.

Thanks,
Keiichi Tokuda

From: Matt Shannon <sms46@xxxxxxxxx>
Subject: [hts-users:01757] bug fix in HGen.c for random parameter generation
Date: Mon, 03 Nov 2008 14:29:40 +0000
Message-ID: <490F0AD4.6090400@xxxxxxxxx>

> There's a bug in the random parameter generation part of 
> Forward_Substitution in HGen.c.  When using random parameter generation 
> (flag 'p'), it causes very distorted output, with a few large artefacts 
> every second.
> 
> The fix is to take the code which adds GaussDeviate to g[t] outside the 
> loop which generates g[t].  Previously there was a feedback effect, 
> where random values of g[t] for small t were influencing the mean value 
> for g[t] for larger t, which mathematically shouldn't happen.
> 
> Manual patch-like diff follows:
> 
>     /* forward substitution */
>     for (t=1; t<=T; t++) {
>        g[t] = r[t];
>        for (i=1; (i<width) && (t-i>0); i++)
>           g[t] -= U[t-i][i+1] * g[t-i];
>        g[t] /= U[t][1];
> -
> -      /* random generation */
> -      if (rFlags&RNDPAR)
> -         g[t] += GaussDeviate(rndParMean, rndParVar);
>     }
> +
> +   if (rFlags&RNDPAR) {
> +      /* random generation */
> +      for (t=1; t<=T; t++) {
> +         g[t] += GaussDeviate(rndParMean, rndParVar);
> +      }
> +   }
> 
> Matt Shannon