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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.functions.continuous.unconstrained;

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

import com.google.common.base.Preconditions;

/**
 * Zettle.
 *
 * Reference: S.K. Mishra, , Technical report, North-Eastern Hill University, India, 2006
 *
 * Minimum:
 * 

 *  ƒ(x*) = -0.003791
 *  x* = (-0.0299, 0)
 *  for x_i in [-5,5]
 * 
 * 
 *
 * Characteristics:
 * 

 * Only defined for 2 dimensions
 * Unimodal
 * Non-Seperable
 * Regular
 * 
 * 
 * R(-5, 5)^2
 */
public class Zettle extends ContinuousFunction {

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

		double x1 = input.get(0).doubleValue();
        double x2 = input.get(1).doubleValue();
        return (Math.pow(((x1 * x1) + (x2 * x2) - 2*x1), 2) + 0.25*x1);
	}
}