Re: [Kaldi-users] Memory requirement for FSTs

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

OK, I remember now, I included --enable-ngram-fsts in the standard
compilation options for Kaldi but I never got round to creating a
recipe to use the openngrm toolkit.
Doing this is definitely possible in Kaldi but it will require both
some scripting and coding work, and I don't think I have time for it
in the next 2-3 months.
Dan


On Sun, Oct 20, 2013 at 2:29 PM, Michael Riley <ri...@go...> wrote:
> 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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