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A modified version of the IREval module (version 4.12) from the lemur project with extensions to better integrate with OpenIMAJ. See http://www.lemurproject.org
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/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * 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 Southampton 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.
 */
/*
 * SetRetrievalComparator.java
 *
 * Created on November 30, 2006, 4:56 PM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package org.lemurproject.ireval;

import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.TreeSet;

import org.apache.commons.math.MathException;
import org.apache.commons.math.distribution.BinomialDistributionImpl;
import org.apache.commons.math.distribution.TDistributionImpl;

/**
 *
 * @author Trevor Strohman
 * @author Jonathon Hare ([email protected])
 */
public class SetRetrievalComparator {
    double[] baseline;
    double[] treatment;
    
    /** 
     * Creates a new instance of SetRetrievalComparator 
     * @param baseline 
     * @param treatment 
     */
    public SetRetrievalComparator( Map baseline, Map treatment ) {
        Set commonQueries = new TreeSet( baseline.keySet() );
        commonQueries.retainAll( treatment.keySet() );

        this.baseline = new double[commonQueries.size()];
        this.treatment = new double[commonQueries.size()];
        int i = 0;
        
        for( String key : commonQueries ) {
            this.baseline[i] = baseline.get(key);
            this.treatment[i] = treatment.get(key);
            i++;
        }
    }

    private double mean( double[] numbers ) {
        double sum = 0;
        for( int i=0; i treatment[i] )
                better++;
        }

        return better;
    }

    /**
     * @return number of times baseline and treatment are equal
     */
    public int countEqual() {
        int same = 0;

        for( int i=0; i baseline[i] )
                treatmentIsBetter++;
            if( treatment[i] != baseline[i] )
                different++;
        }
        
        double pvalue;
		try {
			pvalue = 1 - new BinomialDistributionImpl(different, 0.5).cumulativeProbability(treatmentIsBetter - 1);
		} catch (MathException e) {
			throw new RuntimeException(e);
		}
        
        return pvalue;
    }

    /**
     * @return result of randomized test between baseline and treatment
     */
    public double randomizedTest() {
        double baseMean = mean( baseline );
        double treatmentMean = mean( treatment );
        double difference = treatmentMean - baseMean;
        int batch = 10000;
        
        final int maxIterationsWithoutMatch = 1000000;
        long iterations = 0;
        long matches = 0;
        
        double[] leftSample = new double[baseline.length];
        double[] rightSample = new double[baseline.length];
        Random random = new Random();
        double pValue = 0.0;
        
        while(true) {
            for( int i=0; i iterations )
            if( iterations > estimatedIterations )
                break;

        }
   
        return pValue;
    }
}