ps_lattice_t Struct Reference

Word graph structure used in bestpath/nbest search. More...

#include <pocketsphinx/lattice.h>

Public Member Functions
POCKETSPHINX_EXPORT ps_lattice_t *	ps_lattice_read (struct ps_decoder_s *ps, char const *file)
POCKETSPHINX_EXPORT ps_lattice_t *	ps_lattice_retain (ps_lattice_t *dag)
POCKETSPHINX_EXPORT int	ps_lattice_free (ps_lattice_t *dag)
POCKETSPHINX_EXPORT int	ps_lattice_write (ps_lattice_t *dag, char const *filename)
POCKETSPHINX_EXPORT int	ps_lattice_write_htk (ps_lattice_t *dag, char const *filename)
POCKETSPHINX_EXPORT logmath_t *	ps_lattice_get_logmath (ps_lattice_t *dag)
POCKETSPHINX_EXPORT ps_latnode_iter_t *	ps_latnode_iter (ps_lattice_t *dag)
POCKETSPHINX_EXPORT void	ps_lattice_link (ps_lattice_t *dag, ps_latnode_t *from, ps_latnode_t *to, int32 score, int32 ef)
POCKETSPHINX_EXPORT ps_latlink_t *	ps_lattice_traverse_edges (ps_lattice_t *dag, ps_latnode_t *start, ps_latnode_t *end)
POCKETSPHINX_EXPORT ps_latlink_t *	ps_lattice_traverse_next (ps_lattice_t *dag, ps_latnode_t *end)
POCKETSPHINX_EXPORT ps_latlink_t *	ps_lattice_reverse_edges (ps_lattice_t *dag, ps_latnode_t *start, ps_latnode_t *end)
POCKETSPHINX_EXPORT ps_latlink_t *	ps_lattice_reverse_next (ps_lattice_t *dag, ps_latnode_t *start)
POCKETSPHINX_EXPORT ps_latlink_t *	ps_lattice_bestpath (ps_lattice_t *dag, ngram_model_t *lmset, float32 lwf, float32 ascale)
POCKETSPHINX_EXPORT int32	ps_lattice_posterior (ps_lattice_t *dag, ngram_model_t *lmset, float32 ascale)
POCKETSPHINX_EXPORT int32	ps_lattice_posterior_prune (ps_lattice_t *dag, int32 beam)
POCKETSPHINX_EXPORT int	ps_lattice_n_frames (ps_lattice_t *dag)

Detailed Description

Word graph structure used in bestpath/nbest search.

Member Function Documentation

ps_lattice_read()

POCKETSPHINX_EXPORT ps_lattice_t * ps_lattice_read	(	struct ps_decoder_s *	ps,
		char const *	file
	)

Read a lattice from a file on disk.

Parameters

ps	Decoder to use for processing this lattice, or NULL.
file	Path to lattice file.

Returns

Newly created lattice, or NULL for failure.

ps_lattice_retain()

POCKETSPHINX_EXPORT ps_lattice_t * ps_lattice_retain

(

ps_lattice_t *

dag

)

Retain a lattice.

This function retains ownership of a lattice for the caller, preventing it from being freed automatically. You must call ps_lattice_free() to free it after having called this function.

Returns

pointer to the retained lattice.

ps_lattice_free()

POCKETSPHINX_EXPORT int ps_lattice_free

(

ps_lattice_t *

dag

)

Free a lattice.

Returns

new reference count (0 if dag was freed)

ps_lattice_write()

POCKETSPHINX_EXPORT int ps_lattice_write	(	ps_lattice_t *	dag,
		char const *	filename
	)

Write a lattice to disk.

Returns

0 for success, <0 on failure.

ps_lattice_write_htk()

POCKETSPHINX_EXPORT int ps_lattice_write_htk	(	ps_lattice_t *	dag,
		char const *	filename
	)

Write a lattice to disk in HTK format

Returns

0 for success, <0 on failure.

ps_lattice_get_logmath()

POCKETSPHINX_EXPORT logmath_t * ps_lattice_get_logmath

(

ps_lattice_t *

dag

)

Get the log-math computation object for this lattice

Returns

The log-math object for this lattice. The lattice retains ownership of this pointer, so you should not attempt to free it manually. Use logmath_retain() if you wish to reuse it elsewhere.

ps_latnode_iter()

POCKETSPHINX_EXPORT ps_latnode_iter_t * ps_latnode_iter

(

ps_lattice_t *

dag

)

Start iterating over nodes in the lattice.

Note

No particular order of traversal is guaranteed, and you should not depend on this.

Parameters

dag	Lattice to iterate over.

Returns

Iterator over lattice nodes.

ps_lattice_link()

POCKETSPHINX_EXPORT void ps_lattice_link	(	ps_lattice_t *	dag,
		ps_latnode_t *	from,
		ps_latnode_t *	to,
		int32	score,
		int32	ef
	)

Create a directed link between "from" and "to" nodes, but if a link already exists, choose one with the best link_scr.

ps_lattice_traverse_edges()

POCKETSPHINX_EXPORT ps_latlink_t * ps_lattice_traverse_edges	(	ps_lattice_t *	dag,
		ps_latnode_t *	start,
		ps_latnode_t *	end
	)

Start a forward traversal of edges in a word graph.

Note

A keen eye will notice an inconsistency in this API versus other types of iterators in PocketSphinx. The reason for this is that the traversal algorithm is much more efficient when it is able to modify the lattice structure. Therefore, to avoid giving the impression that multiple traversals are possible at once, no separate iterator structure is provided.

Parameters

dag	Lattice to be traversed.
start	Start node (source) of traversal.
end	End node (goal) of traversal.

Returns

First link in traversal.

ps_lattice_traverse_next()

POCKETSPHINX_EXPORT ps_latlink_t * ps_lattice_traverse_next	(	ps_lattice_t *	dag,
		ps_latnode_t *	end
	)

Get the next link in forward traversal.

Parameters

dag	Lattice to be traversed.
end	End node (goal) of traversal.

Returns

Next link in traversal.

ps_lattice_reverse_edges()

POCKETSPHINX_EXPORT ps_latlink_t * ps_lattice_reverse_edges	(	ps_lattice_t *	dag,
		ps_latnode_t *	start,
		ps_latnode_t *	end
	)

Start a reverse traversal of edges in a word graph.

Note

See ps_lattice_traverse_edges() for why this API is the way it is.

Parameters

dag	Lattice to be traversed.
start	Start node (goal) of traversal.
end	End node (source) of traversal.

Returns

First link in traversal.

ps_lattice_reverse_next()

POCKETSPHINX_EXPORT ps_latlink_t * ps_lattice_reverse_next	(	ps_lattice_t *	dag,
		ps_latnode_t *	start
	)

Get the next link in reverse traversal.

Parameters

dag	Lattice to be traversed.
start	Start node (goal) of traversal.

Returns

Next link in traversal.

ps_lattice_bestpath()

POCKETSPHINX_EXPORT ps_latlink_t * ps_lattice_bestpath	(	ps_lattice_t *	dag,
		ngram_model_t *	lmset,
		float32	lwf,
		float32	ascale
	)

Do N-Gram based best-path search on a word graph.

This function calculates both the best path as well as the forward probability used in confidence estimation.

Returns

Final link in best path, NULL on error.

ps_lattice_posterior()

POCKETSPHINX_EXPORT int32 ps_lattice_posterior	(	ps_lattice_t *	dag,
		ngram_model_t *	lmset,
		float32	ascale
	)

Calculate link posterior probabilities on a word graph.

This function assumes that bestpath search has already been done.

Returns

Posterior probability of the utterance as a whole.

ps_lattice_posterior_prune()

POCKETSPHINX_EXPORT int32 ps_lattice_posterior_prune	(	ps_lattice_t *	dag,
		int32	beam
	)

Prune all links (and associated nodes) below a certain posterior probability.

This function assumes that ps_lattice_posterior() has already been called.

Parameters

beam	Minimum posterior probability for links. This is expressed in the log-base used in the decoder. To convert from linear floating-point, use logmath_log(ps_lattice_get_logmath(), prob).

Returns

number of arcs removed.

ps_lattice_n_frames()

POCKETSPHINX_EXPORT int ps_lattice_n_frames

(

ps_lattice_t *

dag

)

Get the number of frames in the lattice.

Parameters

dag	The lattice in question.

Returns

Number of frames in this lattice.

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The documentation for this struct was generated from the following file:

• pocketsphinx/lattice.h