net.sourceforge.cilib.functions.continuous.unconstrained.Matyas 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;

/**
 * Matyas.
 *
 * Minimum:
 * 

 *  ƒ(x*) = 0.0
 *  x* = (0.0, 0.0)
 *  for x_i in [-10, 10]
 * 
 * 
 *
 * Characteristics:
 * 

 * Only defined for 2 dimensions
 * 
 * 
 *
 * R(-10, 10)^2
 *
 */
public class Matyas extends ContinuousFunction {

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

        double x0 = input.doubleValueOf(0);
        double x1 = input.doubleValueOf(1);

        return 0.26 * (x0 * x0 + x1 * x1) - 0.48 * x0 * x1;
    }
}