org.encog.ml.hmm.alog
Class ForwardBackwardScaledCalculator

java.lang.Object
  extended by org.encog.ml.hmm.alog.ForwardBackwardCalculator
      extended by org.encog.ml.hmm.alog.ForwardBackwardScaledCalculator

public class ForwardBackwardScaledCalculator
extends ForwardBackwardCalculator

The forward-backward algorithm is an inference algorithm for hidden Markov models which computes the posterior marginals of all hidden state variables given a sequence of observations. This version makes use of scaling, and will not generate underflows with long sequences.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.encog.ml.hmm.alog.ForwardBackwardCalculator
ForwardBackwardCalculator.Computation
 
Field Summary
 
Fields inherited from class org.encog.ml.hmm.alog.ForwardBackwardCalculator
alpha, beta, probability
 
Constructor Summary
ForwardBackwardScaledCalculator(MLDataSet oseq, HiddenMarkovModel hmm)
           
ForwardBackwardScaledCalculator(MLDataSet oseq, HiddenMarkovModel hmm, EnumSet<ForwardBackwardCalculator.Computation> flags)
           
 
Method Summary
protected  void computeAlpha(HiddenMarkovModel hmm, MLDataSet oseq)
          Compute alpha.
protected  void computeBeta(HiddenMarkovModel hmm, MLDataSet oseq)
          Compute the beta step.
 double lnProbability()
           
 
Methods inherited from class org.encog.ml.hmm.alog.ForwardBackwardCalculator
alphaElement, betaElement, computeAlphaInit, computeAlphaStep, computeBetaStep, probability
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ForwardBackwardScaledCalculator

public ForwardBackwardScaledCalculator(MLDataSet oseq,
                                       HiddenMarkovModel hmm)

ForwardBackwardScaledCalculator

public ForwardBackwardScaledCalculator(MLDataSet oseq,
                                       HiddenMarkovModel hmm,
                                       EnumSet<ForwardBackwardCalculator.Computation> flags)
Method Detail

computeAlpha

protected void computeAlpha(HiddenMarkovModel hmm,
                            MLDataSet oseq)
Description copied from class: ForwardBackwardCalculator
Compute alpha.

Overrides:
computeAlpha in class ForwardBackwardCalculator
Parameters:
hmm - The hidden markov model.
oseq - The sequence.

computeBeta

protected void computeBeta(HiddenMarkovModel hmm,
                           MLDataSet oseq)
Description copied from class: ForwardBackwardCalculator
Compute the beta step.

Overrides:
computeBeta in class ForwardBackwardCalculator
Parameters:
hmm - The hidden markov model.
oseq - The sequence.

lnProbability

public double lnProbability()


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