bruteforceinferencer.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 salvo.jesus.graph.Vertex;
import salvo.jesus.graph.Graph;
import salvo.jesus.graph.Vertex;
import java.util.Iterator;


/**
 *  Computes the joint of a GraphicalModel by brute-force
 *   calculation.  This is exponentially slow, so it is  mostly 
 *   useful as a sanity check on more complicated algorithms.
 *
 * Created: Wed Sep 17 13:21:13 2003
 *
 * @author <a href="mailto:[e-mail]">Charles Sutton</a>
 * @version $Id: BruteForceInferencer.java,v 1.1 2004/07/15 17:53:31 casutton Exp $
 */
public class BruteForceInferencer 
	extends AbstractInferencer
	implements Inferencer 
{

	DiscretePotential cachedJoint;

	public DiscretePotential joint (UndirectedModel model)
	{ 
		DiscretePotential joint = MultinomialPotential.multiplyAll
															  (model.potentials());
		joint.normalize();
		return joint;
	}

	public DiscretePotential joint (JunctionTree jt)
	{
		MultinomialPotential joint = MultinomialPotential.multiplyAll (jt.potentials ());
		for (Iterator it = jt.sepsetPotentials().iterator(); it.hasNext();) {
			MultinomialPotential pot = (MultinomialPotential) it.next();
			joint.divideBy (pot);
		}
		joint.normalize();
		return joint;
	}

	public void computeMarginals (UndirectedModel mdl)
	{
		cachedJoint = joint (mdl);
	}

	public void computeMarginals (JunctionTree jt)
	{
		cachedJoint = joint (jt);
	}

	public DiscretePotential lookupMarginal (Variable var)
	{
		return cachedJoint.marginalize (var);
	}

	public DiscretePotential lookupMarginal (Clique c)
	{
		return cachedJoint.marginalize (c);
	}

	public double lookupJoint (Assignment assn)
	{
		return cachedJoint.phi (assn);
	}

	public double lookupLogJoint (Assignment assn)
	{
		return Math.log (cachedJoint.phi (assn));
	}

}