cc.mallet.fst.semi_supervised

Class EntropyLattice

java.lang.Object

cc.mallet.fst.semi_supervised.EntropyLattice

public class EntropyLattice
extends java.lang.Object

Runs subsequence constrained forward-backward to compute the entropy of label sequences.

Reference: Gideon Mann, Andrew McCallum "Efficient Computation of Entropy Gradient for Semi-Supervised Conditional Random Fields" HLT/NAACL 2007

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	EntropyLattice.LatticeNode Contains alpha, beta values at a particular input position and state pair.

Constructor Summary

Constructors

Constructor and Description
EntropyLattice(FeatureVectorSequence fvs, double[][] gammas, double[][][] xis, Transducer transducer, Transducer.Incrementor incrementor, double scalingFactor) Runs constrained forward-backward.

Method Summary

Modifier and Type	Method and Description
double	backwardLattice(double[][] gammas, double[][][] xis) Computes the backward entropies (H^beta).
double	forwardLattice(double[][] gammas, double[][][] xis) Computes the forward entropies (H^alpha).
double	getEntropy()
EntropyLattice.LatticeNode	getLatticeNode(int ip, int si)

Methods inherited from class java.lang.Object

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

Constructor Detail

EntropyLattice

public EntropyLattice(FeatureVectorSequence fvs,
                      double[][] gammas,
                      double[][][] xis,
                      Transducer transducer,
                      Transducer.Incrementor incrementor,
                      double scalingFactor)

Runs constrained forward-backward.

If incrementor is null then do not update expectations due to these computations.

The contribution of entropy to the expectations is multiplies by the scaling factor.

Method Detail

getEntropy

public double getEntropy()

forwardLattice

public double forwardLattice(double[][] gammas,
                             double[][][] xis)

Computes the forward entropies (H^alpha).

backwardLattice

public double backwardLattice(double[][] gammas,
                              double[][][] xis)

Computes the backward entropies (H^beta).

getLatticeNode

public EntropyLattice.LatticeNode getLatticeNode(int ip,
                                                 int si)