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

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Here is the source code for de.termininistic.serein.examples.benchmarks.functions.multimodal.SchwefelFunction.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 SchwefelFunction implements BenchmarkFunction {
    public final static Domain DEFAULT_DOMAIN = new Domain(-500, 500);
    private final Domain domain;

    public SchwefelFunction() {
        this(DEFAULT_DOMAIN);
    }

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

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

    @Override
    public RealVector getOptimum(int dimension) {
        return new ArrayRealVector(dimension, 420.9687);
    }

    @Override
    public double map(RealVector v) {
        double[] x = v.toArray();
        int n = x.length;
        double fx = 418.9829 * n;
        for (int i = 0; i < n; i++) {
            fx += -x[i] * Math.sin((Math.sqrt(Math.abs(x[i]))));
        }
        return fx;
    }

}