org.chocosolver.samples.integer.BinPacking Maven / Gradle / Ivy

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/**
 * Copyright (c) 2015, Ecole des Mines de Nantes
 * All rights reserved.
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 *    This product includes software developed by the .
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 *    derived from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY  ''AS IS'' AND ANY
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package org.chocosolver.samples.integer;

import org.chocosolver.samples.AbstractProblem;
import org.chocosolver.solver.ResolutionPolicy;
import org.chocosolver.solver.Solver;
import org.chocosolver.solver.constraints.ICF;
import org.chocosolver.solver.search.loop.monitors.IMonitorSolution;
import org.chocosolver.solver.search.solution.AllSolutionsRecorder;
import org.chocosolver.solver.search.strategy.ISF;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.VF;

/**
 * Bin packing example
 * put items into bins so that bin load is balanced
 *
 * Illustrates the enumeration of optimal solutions
 *
 * @author Jean-Guillaume Fages
 */
public class BinPacking extends AbstractProblem{

	//***********************************************************************************
	// VARIABLES
	//***********************************************************************************

	int nbItems;
	IntVar[] bins;
	int[] weights;
	int nbBins;
	IntVar[] loads;
	IntVar minLoad;

	//***********************************************************************************
	// METHODS
	//***********************************************************************************

	@Override
	public void createSolver() {
		solver = new Solver("bin packing sample");
	}

	@Override
	public void buildModel() {
		// input
		nbItems = d1_w.length;
		weights = d1_w;
		nbBins  = d1_nb;
		// variables
		bins = VF.enumeratedArray("bin",nbItems,0,nbBins-1,solver);
		loads= VF.boundedArray("load",nbBins,0,1000,solver);
		minLoad = VF.bounded("minLoad",0,1000,solver);
		solver.post(ICF.bin_packing(bins,weights,loads,0));
		solver.post(ICF.minimum(minLoad,loads));
	}

	@Override
	public void configureSearch() {
		solver.set(ISF.random_value(bins, 0));
		solver.plugMonitor((IMonitorSolution) () -> {
            String s = minLoad+" : ";
            for(IntVar l:loads){
                s+=" "+l.getValue();
            }
            System.out.println(s);
        });
	}

	@SuppressWarnings("ConstantConditions")
	@Override
	public void solve() {
		int mode = 2;
		switch (mode){
			case 0:// to check
				solver.post(ICF.arithm(minLoad,"=",17));
				solver.set(new AllSolutionsRecorder(solver));
				solver.findAllSolutions();
				break;
			case 1:// one step approach (could be slow)
				solver.findAllOptimalSolutions(ResolutionPolicy.MAXIMIZE, minLoad, false);
				break;
			case 2:// two step approach (find and prove optimum, then enumerate)
				solver.findAllOptimalSolutions(ResolutionPolicy.MAXIMIZE, minLoad, true);
				break;
			default:
				throw new UnsupportedOperationException();
		}
	}

	@Override
	public void prettyOut() {
		System.out.println("There are "+solver.getSolutionRecorder().getSolutions().size()+" optimal solutions");
	}

	//***********************************************************************************
	// DATA
	//***********************************************************************************

	public static void main(String[] args){
	    new BinPacking().execute(args);
	}
	private final static int[] d1_w = new int[]{
			2,5,3,4,12,9,1,0,5,6,2,4
	};
	private final static int d1_nb = 3;
}