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

import net.sourceforge.cilib.functions.ContinuousFunction;
import net.sourceforge.cilib.type.types.container.Vector;

/**
 * Michalewicz funtion 12.
 *
 ** Reference:
 *  http://www.geatbx.com/docu/fcnindex-01.html#TopOfPage
 *
 * Minimum:
 * 

 *  if n=5 then f(x*) = -4.687 
 *  if n=10 then f(x*) = -9.66 
 *  for x_i in [0, pi]
 * 
 * 
 *
 * Characteristics:
 * 
 * Multi-modal
 * Has n! local minima
 * Non-separable
 * 
 *
 * R(0, 3.141592653589793)^10
 *
 */
public class Michalewicz extends ContinuousFunction {

    private static final long serialVersionUID = -4391269929189674709L;
    /**
     * m controls the steepness of the valleys; the larger m, the
     * more difficult the search
     */
    private int m = 10;

    /**
     * {@inheritDoc}
     */
    @Override
    public Double f(Vector input) {
        double sumsq = 0.0;

        for (int i = 0; i < input.size(); i++) {
            double x = input.doubleValueOf(i);
            sumsq += Math.sin(x) * Math.pow(Math.sin(((i+1) * x * x)/Math.PI), 2*m);
        }

        return -sumsq;
    }

    /**
     * Get the current value of M.
     * @return The value of M.
     */
    public int getM() {
        return m;
    }

    /**
     * Set the value of M.
     * @param m The value to set.
     */
    public void setM(int m) {
        this.m = m;
    }
}