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package samples.integer;
import samples.AbstractProblem;
import solver.ResolutionPolicy;
import solver.Solver;
import solver.constraints.ICF;
import solver.search.loop.monitors.IMonitorSolution;
import solver.search.solution.AllSolutionsRecorder;
import solver.search.strategy.ISF;
import solver.variables.IntVar;
import 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(new IMonitorSolution() {
@Override
public void onSolution() {
String s = minLoad+" : ";
for(IntVar l:loads){
s+=" "+l.getValue();
}
System.out.println(s);
}
});
}
@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;
}