opennlp.tools.ml

Class BeamSearch<T>

java.lang.Object

opennlp.tools.ml.BeamSearch<T>

All Implemented Interfaces:

SequenceClassificationModel<T>

public class BeamSearch<T>
extends Object
implements SequenceClassificationModel<T>

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

Field Summary

Fields

Modifier and Type	Field and Description
static String	BEAM_SIZE_PARAMETER

Constructor Summary

Constructors

Constructor and Description
BeamSearch(int size, MaxentModel model) Creates new search object.
BeamSearch(int size, MaxentModel model, int cacheSize)

Method Summary

Modifier and Type	Method and Description
Sequence	bestSequence(T[] sequence, Object[] additionalContext, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator) Finds the sequence with the highest probability.
Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator) Finds the n most probable sequences.
Sequence[]	bestSequences(int numSequences, T[] sequence, Object[] additionalContext, double minSequenceScore, BeamSearchContextGenerator<T> cg, SequenceValidator<T> validator) Returns the best sequence of outcomes based on model for this object.
String[]	getOutcomes() Returns all possible outcomes.

Methods inherited from class java.lang.Object

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

Field Detail

BEAM_SIZE_PARAMETER

public static final String BEAM_SIZE_PARAMETER

See Also:

Constant Field Values

Constructor Detail

BeamSearch

public BeamSearch(int size,
                  MaxentModel model)

Creates new search object.

Parameters:

size - The size of the beam (k).

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

BeamSearch

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

Method Detail

bestSequences

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

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

Specified by:

bestSequences in interface SequenceClassificationModel<T>

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

bestSequences

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

Description copied from interface: SequenceClassificationModel

Finds the n most probable sequences.

Specified by:

bestSequences in interface SequenceClassificationModel<T>

Returns:

bestSequence

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

Description copied from interface: SequenceClassificationModel

Finds the sequence with the highest probability.

Specified by:

bestSequence in interface SequenceClassificationModel<T>

Returns:

getOutcomes

public String[] getOutcomes()

Description copied from interface: SequenceClassificationModel

Returns all possible outcomes.

Specified by:

getOutcomes in interface SequenceClassificationModel<T>

Returns: