[SRILM User List] disambig with Class-based n gram

Andreas Stolcke stolcke at icsi.berkeley.edu
Mon Mar 5 10:09:32 PST 2012

On 3/5/2012 7:17 AM, Reham Al-Majed wrote:
>     Hello ,,
>     I've built class based n-gram by :
>     1- define my classes
>     2- use replace-words-with-classes
>     3- use ngram-count to estimate the LM
>     I want to use this class based n gram model with disambig tool ,,
>     The options (-factored and -count-lm) interpret the LMs as
>     factored and count based LMs ... What about class-based ?  How to
>     tell disambig to interpret the LM as a class-based ?
>     I'm trying to use my class-based as an original n-gram model,
>     however the output for sample test seems strange ... words in the
>     test sample are always disambiguated using the last word in the
>     mapping file !
>      Actually I want the words be disambiguated using the LM
>     probabilities only without considering the probabilities in the
>     mapping file.. I use the options -lmw 1 and -mapw 0 but the output
>     still the same ...
>     In short my questions are :
>     1- Is it possible to use class-based n gram with disabmig tool ?
>     Or should I build my own disambiguator  using  the output of ngram
>     tool ?

Unfortunately disambig currently does not support the use of class-based 
ngram LMs (what is implemented by ngram -classes).
Two workarounds are
1) if feasible, expand the class-ngram LM into a word-ngram LM (using 
ngram -expand-classes).
2) rewrite the class-ngram as a factored LM. This will require some 
investment into understanding the much more general FLM mechanism.

>     2- How to make disambig tool use the probabilities of LM ONLY ?

disambig -mapw 0 will do that.


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