junctiontreemaxproduct.java

这是一个matlab的java实现。里面有许多内容。请大家慢慢捉摸。

/* Copyright (C) 2003 Univ. of Massachusetts Amherst, Computer Science Dept.
   This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit). 
   http://www.cs.umass.edu/~mccallum/mallet
   This software is provided under the terms of the Common Public License,
   version 1.0, as published by http://www.opensource.org.  For further
   information, see the file `LICENSE' included with this distribution. */
package edu.umass.cs.mallet.grmm;

import edu.umass.cs.mallet.base.util.MalletLogger;

import java.util.logging.Logger;

/**
 * Computes max-marginals of a model using junctiontree algorithm.
 *
 * @author Charles Sutton
 * @version $Id: JunctionTreeMaxProduct.java,v 1.1 2004/07/15 17:53:31 casutton Exp $ 
 */
public class JunctionTreeMaxProduct extends JunctionTreeInferencer {

  private static Logger logger = MalletLogger.getLogger (JunctionTreeMaxProduct.class.getName());

  public void computeMarginals (UndirectedModel mdl)
  {
    buildJunctionTree (mdl);
    ViterbiPropagation vp = new ViterbiPropagation ();
    vp.computeMarginals (jtCurrent);
  }

  public DiscretePotential lookupMarginal (Variable var)
  {
    Clique parent = jtCurrent.findParentCluster (var);
    DiscretePotential cpf = jtCurrent.getCPF (parent);
//    logger.finer ("Lookup jt marginal: var "+var+" cluster "+parent);
//    logger.finest (" cpf "+cpf);

    DiscretePotential marginal = cpf.extractMax (var);

//    logger.finest ("Returning "+marginal);
    return marginal;
  }

  public DiscretePotential lookupMarginal (Clique clique)
  {
    Clique parent = jtCurrent.findParentCluster (clique);
    if (parent == null) {
      throw new UnsupportedOperationException
        ("No parent cluster in "+jtCurrent+" for clique "+clique);
    }

    DiscretePotential cpf = jtCurrent.getCPF (parent);
//    logger.finer ("Lookup jt marginal: clique "+clique+" cluster "+parent);
//    logger.finest ("  cpf "+cpf);

    DiscretePotential marginal = cpf.extractMax (clique);

//    logger.finest ("Returning "+marginal);
    return marginal;
  }

}