net.sourceforge.cilib.functions.continuous.unconstrained.SixHumpCamelBack Maven / Gradle / Ivy

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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;

import com.google.common.base.Preconditions;

/**
 * SixHumpCamelBack function.
 *
 * Title: CILib
 * Description: CILib (Computational Intelligence Library)
 * Copyright: Copyright (c) 2004
 * Company: 
 *
 * 
 * Characteristics:
 * 

 * Only defined for 2 dimensions
 * Multimodal
 * Continuous
 * Non Separable
 * 
 * 
 *
 * f(x) = -1.0316; x = (-0.0898, 0.1726); x = (0.0898, -0.1726)
 * x_1 e [-3, 3]; x_2 e [-2, 2]
 *
 * R(-3,3),R(-2,2)
 *
 * @version 1.0
 */
public class SixHumpCamelBack extends ContinuousFunction {

    private static final long serialVersionUID = -3834640752316926216L;

    /**
     * {@inheritDoc}
     */
    @Override
    public Double f(Vector input) {
        Preconditions.checkArgument(input.size() == 2, "SixHumpCamelBack function is only defined for 2 dimensions");

        double x1 = input.doubleValueOf(0);
        double x2 = input.doubleValueOf(1);

        return (4 - 2.1 * x1 * x1 + Math.pow(x1, 4.0) / 3.0) * x1 * x1 + x1 * x2 + 4 * (x2 * x2 - 1) * x2 * x2;
    }
}