[SRILM User List] fsm-to-pfsg & lattice-tool

[Andreas Stolcke]

> 
> I would like to use the lattice-tool in order to prune lattices using the density-prune function.
> 
> I have lattices in AT&T format, and use the following command to convert AT & T fsm format lattices to PFSG format:
> 
> fsm-to-pfsg pfsg_name=New.lat scale=-10000.5 ATTFormat.txt > New.lat
> 
> I am able to print the 1st best path in the lattice without a problem:
> lattice-tool -in-lattice New.lat -nbest-decode 1 -out-nbest-dir ~/Dirs/
> 
> However, when I try to get a pruned lattice using this command:
> 
> lattice-tool -in-lattice New.lat -density-prune 3000 -out-lattice NewPruned.lat
> 
> I get an error "Lattice::prunePosteriors: cannot compute lattice density". Can anyone explain to me what the problem might be.

You cannot compute lattice density from PFSG lattices since LD is defined
as number of nodes per unit time.
PFSG lattices don't record time information for lattice nodes, so the duration associated 
with a lattice is not known.

Andreas