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A library of composable components enabling simpler Computational Intelligence

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/**           __  __
 *    _____ _/ /_/ /_    Computational Intelligence Library (CIlib)
 *   / ___/ / / / __ \   (c) CIRG @ UP
 *  / /__/ / / / /_/ /   http://cilib.net
 *  \___/_/_/_/_.___/
 */
package net.sourceforge.cilib.problem.mappingproblem;

/**
 * Represents a method for calculating the structure distance between two
 * vectors in a MappingProblem.  This specific one simply assumes that we
 * are looking at some "linear" structure and that all input vectors logically
 * follows on one another.  This can sometimes be the case, but I don't see
 * many situations where this will make a hell of a lot of sense...
 *
 */
public class LinearDistanceMetric implements DistanceMetric {
    /**
     * Gets called by CurvilinearDistEvaluator to indicate the precise problem
     * to make use of.  It is recommended that the results of the distances
     * be calculated and placed into some kind of matrix at this point to allow
     * for faster execution.
     *
     * @param prob The underlying MappingProblem.
     */
    public void setMappingProblem(MappingProblem prob) {
        int nvect = prob.getNumInputVectors();
        distanceOffsets = new double[nvect];
        double currentOffset = 0.0;
        distanceOffsets[0] = 0.0;

        for(int i = 1; i < nvect; i++) {
            currentOffset += prob.getDistanceInputVect(i - 1, i);
            distanceOffsets[i] = currentOffset;
        }

        totalDistance = currentOffset + prob.getDistanceInputVect(nvect - 1, 0);
    }

    /**
     * Gets called by CurvilinearDistEvaluator to request the distance between
     * two vectors to be returned.
     *
     * @param i The index of the "from" vector.
     * @param j The index of the "to" vector.
     *
     * @return The distance between to two vectors.
     */
    public double getDistance(int i, int j) {
        double distance = distanceOffsets[j] - distanceOffsets[i];

        // if(j < i)
        if(distance < 0.0) {
            distance = -distance;
        }

        if(doloop && totalDistance - distance < distance) {
            distance = totalDistance - distance;
        }

        return distance;
    }

    /**
     * Sets the looping status.  If the looping status is active it is assumed
     * that we are working with some looping structure, ie, the last point goes
     * back to the first.  In this case there are two possible directions from
     * one vector to another, the shortest one is returned.
     *
     * @param loopstatus What the loopstatus should be (true/false).
     */
    public void setLoopStatus(boolean loopstatus) {
        doloop = loopstatus;
    }

    /**
     * Retrieves the looping status.  {@link setLoopStatus}
     *
     * @return The current loop status.
     */
    public boolean getLoopStatus() {
        return doloop;
    }

    private double []distanceOffsets;
    private double totalDistance;
    private boolean doloop;
}