opennlp.tools.util

Class BeamSearch<T>

java.lang.Object

opennlp.tools.util.BeamSearch<T>

public class BeamSearch<T>
extends Object

Performs k-best search over sequence. This is based on the description in Ratnaparkhi (1998), PhD diss, Univ. of Pennsylvania.

See Also:

Sequence, SequenceValidator, BeamSearchContextGenerator

Constructor Summary

Constructors

Constructor and Description
BeamSearch(int size, BeamSearchContextGenerator<T> cg, MaxentModel model) Creates new search object.
BeamSearch(int size, BeamSearchContextGenerator<T> cg, MaxentModel model, int cacheSize)
BeamSearch(int size, BeamSearchContextGenerator<T> cg, MaxentModel model, SequenceValidator<T> validator, int cacheSize)

Method Summary

Methods

Modifier and Type	Method and Description
Sequence	bestSequence(T[] sequence, Object[] additionalContext) Returns the best sequence of outcomes based on model for this object.
Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext)
Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext, double minSequenceScore) Returns the best sequence of outcomes based on model for this object.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BeamSearch

public BeamSearch(int size,
          BeamSearchContextGenerator<T> cg,
          MaxentModel model)

Creates new search object.

Parameters:

size - The size of the beam (k).

cg - the context generator for the model.

model - the model for assigning probabilities to the sequence outcomes.

BeamSearch

public BeamSearch(int size,
          BeamSearchContextGenerator<T> cg,
          MaxentModel model,
          int cacheSize)

BeamSearch

public BeamSearch(int size,
          BeamSearchContextGenerator<T> cg,
          MaxentModel model,
          SequenceValidator<T> validator,
          int cacheSize)

Method Detail

bestSequences

public Sequence[] bestSequences(int numSequences,
                       T[] sequence,
                       Object[] additionalContext)

bestSequences

public Sequence[] bestSequences(int numSequences,
                       T[] sequence,
                       Object[] additionalContext,
                       double minSequenceScore)

Returns the best sequence of outcomes based on model for this object.

Parameters:

numSequences - The maximum number of sequences to be returned.

sequence - The input sequence.

additionalContext - An Object[] of additional context. This is passed to the context generator blindly with the assumption that the context are appropiate.

minSequenceScore - A lower bound on the score of a returned sequence.

Returns:

An array of the top ranked sequences of outcomes.

bestSequence

public Sequence bestSequence(T[] sequence,
                    Object[] additionalContext)

Returns the best sequence of outcomes based on model for this object.

Parameters:

sequence - The input sequence.

additionalContext - An Object[] of additional context. This is passed to the context generator blindly with the assumption that the context are appropiate.

Returns:

The top ranked sequence of outcomes or null if no sequence could be found