abstractinferencer.java

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/* 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;


/**
 * Abstract base class for inferencers.  This simply throws
 *  an UnsupportedOperationException for all methods, which
 *  is useful for subclasses that want to implement only
 *  specific inference functionality.
 *
 * Created: Mon Oct  6 17:01:21 2003
 *
 * @author <a href="mailto:[e-mail]">Charles Sutton</a>
 * @version $Id: AbstractInferencer.java,v 1.2 2004/07/22 00:37:38 casutton Exp $
 */
abstract public class AbstractInferencer implements Inferencer, Cloneable {

// Implementation of edu.umass.cs.mallet.grmm.graphical.Inferencer

	public void computeMarginals(DirectedModel undirectedModel) {
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" doesn't support undirected models.");				
	}

	public void computeMarginals(UndirectedModel undirectedModel) {
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" doesn't support undirected models.");				
	}

	public void computeMarginals(JunctionTree junctionTree) {
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" doesn't support junction trees.");				
	}

	public double lookupJoint (Assignment assn)
	{
		return Math.exp (lookupLogJoint (assn));
	}

	public double lookupLogJoint (Assignment assn)
	{
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" doesn't compute joint probabilities.");
	}

	public DiscretePotential lookupMarginal (Clique c)
	{
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" doesn't compute marginals of arbitrary cliques.");
	}

	// xxx Should be generalized to GraphicalModel
	public double query (UndirectedModel mdl, Assignment assn)
	{
		// Computes joint of assignment using chain rule
		UndirectedModel mdl2 = mdl.duplicate();
		double marginal = 1.0;
		for (int i = 0; i < assn.size(); i++) {
			Variable var = assn.getVariable (i);
			computeMarginals (mdl2);
			DiscretePotential ptl = lookupMarginal (var);
			marginal *= ptl.phi (assn);
			mdl2.setObserved (var, assn.get (var));
		}
		return marginal;
	}

	public double query (DirectedModel mdl, Assignment assn)
	{
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" can't query assignments.");
	}

	public double query (JunctionTree mdl, Assignment assn)
	{
		throw new UnsupportedOperationException 
			(this.getClass().getName()+" can't query assignments.");
	}

	abstract public DiscretePotential lookupMarginal(Variable variable);

	public Inferencer duplicate () {
		try {
			return (Inferencer) clone();
		} catch (CloneNotSupportedException e) {
			throw new RuntimeException (e);
		}
	}
	
} // AbstractInferencer