edu.stanford.nlp.ie

Class UniformPrior<IN extends CoreMap>

java.lang.Object

edu.stanford.nlp.ie.UniformPrior<IN>

All Implemented Interfaces:

SequenceListener, SequenceModel

public class UniformPrior<IN extends CoreMap>
extends Object
implements SequenceModel, SequenceListener

Uniform prior to be used for generic Gibbs inference in the ie.crf.CRFClassifier

Author:

Mihai

Field Summary

Fields

Modifier and Type	Field and Description
protected int	backgroundSymbol
protected Index<String>	classIndex
protected List<IN>	doc
protected int	numClasses
protected int[]	possibleValues
protected int[]	sequence

Constructor Summary

Constructors

Constructor and Description
UniformPrior(String backgroundSymbol, Index<String> classIndex, List<IN> doc)

Method Summary

Methods

Modifier and Type	Method and Description
int[]	getPossibleValues(int position) Return the valid sequence labels (as integer indices) for a particular position in the sequence.
int	leftWindow() How many label positions to the left influence the label assignment at a particular position.
int	length()
int	rightWindow() How many label positions to the right influence the label assignment at a particular position.
double	scoreOf(int[] sequence) Computes the score assigned by this model to the whole sequence.
double	scoreOf(int[] sequence, int position) Computes the score of the element at the given position in the sequence, conditioned on the values of the elements in all other positions of the provided sequence.
double[]	scoresOf(int[] sequence, int position) Computes the scores of labels for the element at the given position in the sequence, conditioned on the values of the labels at all other positions of the provided sequence.
void	setInitialSequence(int[] sequence) Informs this sequence listener that the value of the whole sequence is initialized to sequence
void	updateSequenceElement(int[] sequence, int pos, int oldVal) Informs this sequence listener that the value of the element at position pos has changed.

Methods inherited from class java.lang.Object

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

Field Detail

sequence

protected int[] sequence

backgroundSymbol

protected int backgroundSymbol

numClasses

protected int numClasses

possibleValues

protected int[] possibleValues

classIndex

protected Index<String> classIndex

doc

protected List<IN extends CoreMap> doc

Constructor Detail

UniformPrior

public UniformPrior(String backgroundSymbol,
            Index<String> classIndex,
            List<IN> doc)

Method Detail

scoreOf

public double scoreOf(int[] sequence)

Description copied from interface: SequenceModel

Computes the score assigned by this model to the whole sequence. Typically this will be an unnormalized probability in log space (since the probabilities are small).

Specified by:

scoreOf in interface SequenceModel

Parameters:

sequence - The sequence of labels to compute a score for

Returns:

The score for the entire sequence

scoresOf

public double[] scoresOf(int[] sequence,
                int position)

Description copied from interface: SequenceModel

Computes the scores of labels for the element at the given position in the sequence, conditioned on the values of the labels at all other positions of the provided sequence. The returned array elements correspond index-by-index to the possible values returned by getPossibleValues(int). The label at sequence[position] is ignored in the calculations. The scores are often given as an unnormalized log conditional distribution over possible labels. Otherwise, they may be probabilities. If it is a probability distribution, conceptually, the scores should sum to 1 (perhaps after transforming them). Note that implementations often alter sequence[position] to do their calculations, and so access to the array isn't threadsafe, but should restore its value afterwards.

Specified by:

scoresOf in interface SequenceModel

Parameters:

sequence - The sequence containing the rest of the values to condition on

position - The position of the element to give a distribution for

Returns:

The scores of the possible tokens at the specified position in the sequence

getPossibleValues

public int[] getPossibleValues(int position)

Description copied from interface: SequenceModel

Return the valid sequence labels (as integer indices) for a particular position in the sequence. Since the sequence is padded at each end, typically sequence items 0...leftWindow-1 are null, leftWindow...length+leftWindow-1 are words, length+leftWindow...length+leftWindow+rightWindow-1 are null.

Specified by:

getPossibleValues in interface SequenceModel

Parameters:

position - The position

Returns:

The set of possible int values at this position, as an int array

leftWindow

public int leftWindow()

Description copied from interface: SequenceModel

How many label positions to the left influence the label assignment at a particular position.

Specified by:

leftWindow in interface SequenceModel

Returns:

The size of the left window used by this sequence model

length

public int length()

Specified by:

length in interface SequenceModel

Returns:

The length of the sequences modeled by this SequenceModel. This is its real length, not including the leftWindow() + rightWindow() of extra padding positions.

rightWindow

public int rightWindow()

Description copied from interface: SequenceModel

How many label positions to the right influence the label assignment at a particular position.

Specified by:

rightWindow in interface SequenceModel

Returns:

the size of the right window used by this sequence model

scoreOf

public double scoreOf(int[] sequence,
             int position)

Description copied from interface: SequenceModel

Computes the score of the element at the given position in the sequence, conditioned on the values of the elements in all other positions of the provided sequence. Typically, this is an unnormalized log conditional probability of the label at the given position in the sequence, given the input data nd the other labels.

Specified by:

scoreOf in interface SequenceModel

Parameters:

sequence - The sequence containing the prediction and the rest of the labels to condition on

position - The position of the element to give a score for

Returns:

The score of the label at the specified position in the sequence

setInitialSequence

public void setInitialSequence(int[] sequence)

Description copied from interface: SequenceListener

Informs this sequence listener that the value of the whole sequence is initialized to sequence

Specified by:

setInitialSequence in interface SequenceListener

updateSequenceElement

public void updateSequenceElement(int[] sequence,
                         int pos,
                         int oldVal)

Description copied from interface: SequenceListener

Informs this sequence listener that the value of the element at position pos has changed. This allows this sequence model to update its internal model if desired.

Specified by:

updateSequenceElement in interface SequenceListener