de.termininistic.serein.examples.benchmarks.functions.multimodal.AckleyFunction.java Source code

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Here is the source code for de.termininistic.serein.examples.benchmarks.functions.multimodal.AckleyFunction.java

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/**
 * Copyright (C) 2015 Tobias Uhlig (tobias.uhlig@unibw.de)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.termininistic.serein.examples.benchmarks.functions.multimodal;

import org.apache.commons.math3.linear.ArrayRealVector;
import org.apache.commons.math3.linear.RealVector;

import de.termininistic.serein.examples.benchmarks.functions.BenchmarkFunction;
import de.termininistic.serein.examples.benchmarks.functions.Domain;

public class AckleyFunction implements BenchmarkFunction {

    public final static Domain DEFAULT_DOMAIN = new Domain(-32.768, 32.768);
    private final Domain domain;

    public AckleyFunction() {
        this(DEFAULT_DOMAIN);
    }

    public AckleyFunction(Domain domain) {
        this.domain = domain;
    }

    @Override
    public double map(RealVector v) {
        double[] x = v.toArray();
        int n = x.length;
        double sum1 = 0.0, sum2 = 0.0;

        for (int i = 0; i < n; i++) {
            sum1 += x[i] * x[i];
            sum2 += Math.cos(2 * Math.PI * x[i]);
        }
        double fx = -20 * Math.exp(-0.2 * Math.sqrt(sum1 / n)) - Math.exp(sum2 / n) + 20 + Math.E;
        return fx;
    }

    @Override
    public Domain getDomain() {
        return domain;
    }

    @Override
    public RealVector getOptimum(int dimension) {
        return new ArrayRealVector(dimension, 0.0);
    }

}