xf.xfvrp.opt.construct.XFVRPSavingsLamda Maven / Gradle / Ivy

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Solver for realistic vehicle routing problems

There is a newer version: 11.4.6-RELEASE

package xf.xfvrp.opt.construct;

import xf.xfvrp.base.Quality;
import xf.xfvrp.opt.Solution;


/** 
 * Copyright (c) 2012-present Holger Schneider
 * All rights reserved.
 *
 * This source code is licensed under the MIT License (MIT) found in the
 * LICENSE file in the root directory of this source tree.
 *
 *
 * Contains the Savings optimization procedure, where
 * the acceptance criteria is parameterized by the lamda 
 * value. Six variants with different lamda values (0.6, 1, 1.4, 1.6, 2, 3) 
 * are calculated and best result is taken.
 * 
 * @author hschneid
 *
 */
public class XFVRPSavingsLamda extends XFVRPSavings {

	private final float[] lamdaParameters = new float[]{0.6f, 1, 1.4f, 1.6f, 2, 3};
	
	/*
	 * (non-Javadoc)
	 * @see de.fhg.iml.vlog.xftour.xfvrp.opt.construct.XFVRPSavings#execute(de.fhg.iml.vlog.xftour.model.XFNode[])
	 */
	@Override
	public Solution execute(Solution solution) {
		Solution best = super.execute(solution.copy());
		Solution sol;
		Quality quality, bestQuality;

		bestQuality = check(best);
		
		for (float l : lamdaParameters) {
			this.lamda = l;
			sol = super.execute(solution.copy());
			quality = check(sol);
			if(quality.getFitness() < bestQuality.getFitness()) {
				best = sol;
				bestQuality = quality;
			}			
		}
		
		return best;
	}

}