/*
 * Copyright (c) 2005, 2006, Regents of the University of California
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.  
 *
 * * Neither the name of the University of California, Berkeley nor
 *   the names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior 
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package blog;

import java.util.*;
import common.Util;

public class RejectionSampler extends Sampler {
    

    public RejectionSampler(Model model, Properties properties) {
	super(model);

	String intBoundStr = properties.getProperty("intBound");
	if (intBoundStr != null) {
	    try {
		intBound = Integer.parseInt(intBoundStr);
	    } catch (NumberFormatException e) {
		Util.fatalError("Invalid intBound: " + intBoundStr);
	    }
	}

	String depthBoundStr = properties.getProperty("depthBound");
	if (depthBoundStr != null) {
	    try {
		depthBound = Integer.parseInt(depthBoundStr);
	    } catch (NumberFormatException e) {
		Util.fatalError("Invalid depthBound: " + depthBoundStr);
	    }
	}
    }

    public void initialize(Evidence evidence, List queries) {
	super.initialize(evidence, queries);
	requireComplete = false;

	numSamplesThisTrial = 0;
	numAcceptedThisTrial = 0;

	curWorld = null;
    }

    

    public void initializeCompleteSampling() {
	super.initialize(new Evidence(), Collections.EMPTY_LIST);
	requireComplete = true;

	numSamplesThisTrial = 0;
	numAcceptedThisTrial = 0;

	curWorld = null;
    }	

    public void nextSample() {
	if (Util.verbose()) {
	    System.out.println();
	    System.out.println("Sampling world...");
	}
	curWorld = new WorldInProgress(model, evidence, intBound, depthBound);

	// Find the first variable that is supported but not instantiated.  
	// Instantiate it.  Repeat until all evidence and query variables 
	// are determined.
	while (!isCurWorldSufficient()) {
	    boolean varInstantiated = false;

	    if (curWorld.isComplete()) {
		Util.fatalError("World is complete (up to specified integer "
				+ "and depth bounds) but does not determine "
				+ "values for evidence and queries.", 
				false);
	    }

	    for (WorldInProgress.UninstVarIterator iter 
		     = curWorld.uninstVarIterator(); iter.hasNext(); ) {
		VarWithDistrib var = (VarWithDistrib) iter.next();
		DependencyModel.Distrib distrib = var.getDistrib
		    (new DefaultEvalContext(curWorld, false));
		if (distrib == null) {
		    if (Util.verbose()) {
			System.out.println("Not supported yet: " + var);
		    } 
		} else {
		    // var is supported
		    if (Util.verbose()) {
			System.out.println("Instantiating: " + var);
		    }
		    iter.setValue(distrib.getCPD().sampleVal
				  (distrib.getArgValues(), var.getType()));

		    varInstantiated = true;
		    break; // start again from first uninstantiated var
		}
	    }

	    if (!varInstantiated) {
		String msg = ("World is not complete, but no basic random "
			      + "variable is supported.  Please check for "
			      + "a possible cycle in your model.");
		if ((intBound >= 0) || (depthBound >= 0)) {
		    msg = (msg + "  This problem could also be caused by "
			   + "the intBound and depthBound flags.");
		}
		Util.fatalError(msg, false);
	    }
	}

	// See if world happens to satisfy the evidence
	curWorldAccepted = evidence.isTrue(curWorld);

	++numSamplesThisTrial;
	if (curWorldAccepted) {
	    ++numAcceptedThisTrial;
	}
    }

    public PartialWorld getLatestWorld() {
	if (curWorld == null) {
	    throw new IllegalStateException("Sampler has no latest sample.");
	}
	return curWorld;
    }

    public double getLatestWeight() {
	if (curWorld == null) {
	    throw new IllegalStateException("Sampler has no latest sample.");
	}
	return (curWorldAccepted ? 1.0 : 0.0);
    }

    public void printStats() {
	System.out.println("=== Rejection Sampler Trial Stats ===");
	if (numSamplesThisTrial > 0) {
	    System.out.println
		("Fraction of worlds accepted (this trial): " 
		 + (numAcceptedThisTrial / (double) numSamplesThisTrial));
	} else {
	    System.out.println("No samples this trial.");
	}
    }

    private boolean isCurWorldSufficient() {
	if (requireComplete) {
	    return curWorld.isComplete();
	}

	if (!evidence.isDetermined(curWorld)) {
	    return false;
	}

	for (Iterator iter = queries.iterator(); iter.hasNext(); ) {
	    Query q = (Query) iter.next();
	    for (BayesNetVar var : q.getVariables()) {
		if (!var.isDetermined(curWorld)) {
		    return false;
		}
	    }
	}

	return true;
    }

    private int intBound = -1;
    private int depthBound = -1;
    private boolean requireComplete = false;

    private WorldInProgress curWorld;
    private boolean curWorldAccepted;

    private int numSamplesThisTrial;
    private int numAcceptedThisTrial;
}

This file was generated on Tue Jun 08 17:53:36 PDT 2010 from file RejectionSampler.java
by the ilog.language.tools.Hilite Java tool written by Hassan Aït-Kaci