trellis Class Reference

The class viterbi stores the two maps for each observation: The delta map stores the maximum probability for each state in that observation, the phi map stores the backpath to maximize the probability. More...

#include <hmm_tagger.h>

List of all members.

Classes
class	element
	Each trellis node contains an ordered set of paths. More...
Public Member Functions
	trellis (int, unsigned int kb=1)
	Constructor.
	~trellis ()
	Destructor.
void	insert (int, const std::wstring &, const std::wstring &, int kb, double)
	add new element to the trellis
double	delta (int, const std::wstring &, unsigned int k=0)
	retieve delta component for kth best path (count starts at 0) for given T and state.
std::pair< std::wstring, int >	phi (int, const std::wstring &, unsigned int k=0)
	retieve phi component for kth best path (count starts at 0) for given T and state
int	nbest (int, const std::wstring &)
	Get number of elements in kbest set for given time&state (at most kbest, maybe less)
Static Public Attributes
static float	ZERO_logprob
	log prob for zero
Private Attributes
std::map< std::wstring, std::multiset< element > > *	trl
	Trellis: array of columns.
unsigned int	kbest
	Number of kbest paths to store.

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Detailed Description

The class viterbi stores the two maps for each observation: The delta map stores the maximum probability for each state in that observation, the phi map stores the backpath to maximize the probability.

An instance of this class is created for each sentence to be tagged, and destroyed when work is finished.

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Constructor & Destructor Documentation

trellis::trellis	(	int	T,
		unsigned int	kb = 1
	)

Constructor.

Constructor: Create dynammic storage for delta and phi tables in the trellis.

trellis::~trellis

(

)

Destructor.

Destructor: Free dynammic storage for delta and phi tables stored in the trellis.

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Member Function Documentation

double trellis::delta	(	int	,
		const std::wstring &	,
		unsigned int	k = 0
	)

retieve delta component for kth best path (count starts at 0) for given T and state.

Get delta component for kth best path (count from 0)

References ERROR_CRASH.

void trellis::insert	(	int	,
		const std::wstring &	,
		const std::wstring &	,
		int	kb,
		double
	)

add new element to the trellis

insert a new arc in the trellis.

Time t, state s, prev state sa, prob p

References util::int2wstring(), and TRACE.

int trellis::nbest	(	int	,
		const std::wstring &
	)

Get number of elements in kbest set for given time&state (at most kbest, maybe less)

Get number of elements in kbest set for time t, state s.

pair< wstring, int > trellis::phi	(	int	,
		const std::wstring &	,
		unsigned int	k = 0
	)

retieve phi component for kth best path (count starts at 0) for given T and state

Get phi component for kth best path (count from 0)

References ERROR_CRASH.

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Member Data Documentation

unsigned int trellis::kbest [private]

Number of kbest paths to store.

std::map<std::wstring, std::multiset<element> >* trellis::trl [private]

Trellis: array of columns.

Each column associates each state with a set of path elements

float trellis::ZERO_logprob [static]

log prob for zero

Referenced by hmm_tagger::annotate(), and hmm_tagger::ProbPi_log().

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The documentation for this class was generated from the following files:

• hmm_tagger.h
• hmm_tagger.cc