Re: [Kaldi-developers] Baum-Welch training for HMMs

[Daniel P. <dp...@gm...>]

>
> However, I am not so sure how to implement the Backward algorithm, since I
> must traverse the edges in the FST backwards (to do the backward pass in
> O(T * (V + E))), and OpenFST does not support this AFAIK. Also, I am not
> sure if simply transposing the FST would work, since I would have many
> initial states... Any suggestion on that?
>
It should be possible to handle this by arranging your code in the right
way, e.g. first iterate over the start-state of the arc.

> > This would create a difficulty for converting alignments though (this
> happens
> > when bootstrapping later systems, e.g. starting tri2 from tri1).  You
> would
> > probably have to just to Viterbi for that one stage.
>
> I am not sure what you mean. Could you extend your explanation or point to
> a recipe where you had to overcome this difficulty?
>
I mean the program convert-ali wouldn't work unless you had alignments.
Dan


> Many thanks for your help and advices,
>
> Joan Puigcerver.
>