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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;

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

 *  ƒ(x*) = -43.31586206998933
 *  x* = (5.90133, 0.5)
 *  for x_i in [-30,30]
 * 
 * 
 *
 * Characteristics:
 * 

 * Only defined for 2 dimensions
 * Multimodal
 * Seperable
 * Regular
 * 
 * 
 * R(-30, 30)^2
 */
public class Chichinadze extends ContinuousFunction {

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

		double x1 = input.get(0).doubleValue();
		double x2 = input.get(1).doubleValue();

		double cos = Math.cos(Math.PI * x1 / 2);
		double sin = Math.sin(5*Math.PI*x1);
		double ePow = Math.exp(-0.5 * ((x2 - 0.5) * (x2 - 0.5)));

		return (x1*x1) - 12 * (x1) + 11 + 10*cos + 8 * sin - Math.pow((1/5.0), 0.5)* ePow;
	}
}