Re: [Kaldi-users] Memory requirement for FSTs

[Michael R. <ri...@go...>]

It is included but you need to compile with *--enable-ngram-fsts*.
Similarly for the other extension formats. My own suggestion would be to
use a large LM represented as an NGramFst in 2nd pass lattice rescoring and
entropy prune that model to a modest size for a first pass with a static
(H)CLG. With a reasonable lattice size, you'll get virtually no search
errors.

The NGramFst expects a specific ngram format; www.opengrm.org describes and
offers tools to train and convert from DARPA format.

-m

On Sun, Oct 20, 2013 at 2:10 PM, Daniel Povey <dp...@gm...> wrote:

> Mike: NgramFst isn't included in the standard OpenFst distribution, is it?
> Dan
>
>
> On Sun, Oct 20, 2013 at 2:08 PM, Michael Riley <ri...@go...> wrote:
> > I don't know much about how ngram FSTs are used in Kaldi or the
> > characteristics of their implementations, but I do know that for sheer
> > OpenFst representation:
> >
> >   VectorFst and ConstFst (the standard mutable and immutable OpenFst
> reps)
> > use about 20 bytes per state and 16 bytes per arc while NGramFst,
> specific
> > to ngram models (see here), use about 8 bytes per state and 8 bytes per
> arc.
> > The last, for representing at the word level, is the most compact and is
> > used, in general, in a rescoring or on-the-fly composition mode.  There
> are
> > also various compact FST formats (see here) that can represent other
> > specific FSTs (and is extensible).
> >
> >   With 64 bit compilation, you are limited by how much memory you have
> for
> > those reps and of course. Hope that helps.
> >
> > On Fri, Oct 18, 2013 at 12:06 AM, E <oth...@ao...> wrote:
> >>
> >> Thanks a lot for the answers and possible solutions.
> >>
> >> Few questions-
> >>
> >> What is the maximum size trigram language model supported by FST? I
> tried
> >> to use Gigaword LM (64k vocab), mkgraph.sh ran for a long time but
> crashed
> >> afterwords. So I want to know if there is a theoretical limit on size of
> >> language model that can be integrated with Kaldi.
> >>
> >> I will try to make HCLG.fst with gigaword again (with triphone AM), but
> >> has anyone tried to build it with LM of this size successfully, if so,
> what
> >> were the system requirements (RAM) and final FST size in mega/gigabytes?
> >>
> >>
> >>
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