Package opennlp.tools.ml

Class BeamSearch

java.lang.Object

opennlp.tools.ml.BeamSearch

All Implemented Interfaces:

SequenceClassificationModel

public class BeamSearch
extends Object
implements SequenceClassificationModel

Performs k-best search over a sequence.

This is based on the description in Ratnaparkhi (1998), PhD diss, Univ. of Pennsylvania.

See Also:

• Sequence
• SequenceValidator
• BeamSearchContextGenerator

Field Summary

Fields

Modifier and Type	Field	Description
static final String	BEAM_SIZE_PARAMETER

Constructor Summary

Constructors

Constructor	Description
BeamSearch(int size, MaxentModel model)	Initializes a BeamSearch instance.
BeamSearch(int size, MaxentModel model, int cacheSize)	Initializes a BeamSearch instance.

Method Summary

Modifier and Type	Method	Description
<T> Sequence	bestSequence(T[] sequence, Object[] additionalContext, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator)	Computes the best sequence of outcomes based on the MaxentModel.
<T> Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext, double minSequenceScore, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator)	Computes the best sequence of outcomes based on the MaxentModel.
<T> Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator)	Computes the best sequence of outcomes based on the MaxentModel.
String[]	getOutcomes()

Methods inherited from class java.lang.Object

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

Field Details

BEAM_SIZE_PARAMETER

public static final String BEAM_SIZE_PARAMETER

See Also:

• Constant Field Values

Constructor Details

BeamSearch

public BeamSearch(int size,
 MaxentModel model)

Initializes a BeamSearch instance.

Parameters:

size - The size of the beam (k).

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

BeamSearch

public BeamSearch(int size,
 MaxentModel model,
 int cacheSize)

Initializes a BeamSearch instance.

Parameters:

size - The size of the beam (k).

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

cacheSize - The capacity of the Cache to use.

Method Details

bestSequences

public <T> Sequence[] bestSequences(int numSequences,
 T[] sequence,
 Object[] additionalContext,
 double minSequenceScore,
 BeamSearchContextGenerator<T> cg,
 SequenceValidator<T> validator)

Computes the best sequence of outcomes based on the MaxentModel.

Specified by:

bestSequences in interface SequenceClassificationModel

Parameters:

numSequences - The number of sequences.

sequence - The input BeamSearch sequence.

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

minSequenceScore - The minimum sequence score to use.

cg - The context generator to use.

validator - The SequenceValidator to validate sequences.

Returns:

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

bestSequences

public <T> Sequence[] bestSequences(int numSequences,
 T[] sequence,
 Object[] additionalContext,
 BeamSearchContextGenerator<T> cg,
 SequenceValidator<T> validator)

Computes the best sequence of outcomes based on the MaxentModel.

Specified by:

bestSequences in interface SequenceClassificationModel

Parameters:

numSequences - The number of sequences.

sequence - The input BeamSearch sequence.

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

cg - The context generator to use.

validator - The SequenceValidator to validate sequences.

Returns:

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

bestSequence

public <T> Sequence bestSequence(T[] sequence,
 Object[] additionalContext,
 BeamSearchContextGenerator<T> cg,
 SequenceValidator<T> validator)

Computes the best sequence of outcomes based on the MaxentModel.

Specified by:

bestSequence in interface SequenceClassificationModel

Parameters:

sequence - The input BeamSearch sequence.

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

cg - The context generator to use.

validator - The SequenceValidator to validate sequences.

Returns:

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

getOutcomes

public String[] getOutcomes()

Specified by:

getOutcomes in interface SequenceClassificationModel

Returns:

Retrieves all possible outcomes.