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package solver.constraints.nary;
import gnu.trove.map.hash.THashMap;
import memory.IEnvironment;
import memory.IStateInt;
import solver.Solver;
import solver.constraints.Propagator;
import solver.constraints.PropagatorPriority;
import solver.exception.ContradictionException;
import solver.variables.IntVar;
import util.ESat;
import util.objects.setDataStructures.ISet;
import util.objects.setDataStructures.SetFactory;
import util.objects.setDataStructures.SetType;
import util.tools.ArrayUtils;
/**
* Incremental propagator which restricts the number of loops:
* |{succs[i]=i+offSet}| = nbLoops
*
* @author Jean-Guillaume Fages
*/
public class PropKLoops extends Propagator<IntVar> {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
// number of nodes
private int n;
// offset (usually 0 but 1 with MiniZinc)
private int offSet;
// uninstantiated variables that can be loops
private ISet possibleLoops;
private IStateInt nbMinLoops;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Incremental propagator which restricts the number of loops:
* |{succs[i]=i+offSet}| = nbLoops
*
* @param succs
* @param offSet
* @param nbLoops
*/
public PropKLoops(IntVar[] succs, int offSet, IntVar nbLoops) {
super(ArrayUtils.append(succs, new IntVar[]{nbLoops}), PropagatorPriority.UNARY, true);
this.n = succs.length;
this.offSet = offSet;
IEnvironment environment = solver.getEnvironment();
this.possibleLoops = SetFactory.makeStoredSet(SetType.BIPARTITESET, n, solver);
this.nbMinLoops = environment.makeInt();
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public void propagate(int evtmask) throws ContradictionException {
possibleLoops.clear();
nbMinLoops.set(0);
for (int i = 0; i < n; i++) {
if (vars[i].contains(i + offSet)) {
if (vars[i].isInstantiated()) {
nbMinLoops.add(1);
} else {
possibleLoops.add(i);
}
}
}
filter();
}
private void filter() throws ContradictionException {
int nbMin = nbMinLoops.get();
int nbMax = nbMin + possibleLoops.getSize();
vars[n].updateLowerBound(nbMin, aCause);
vars[n].updateUpperBound(nbMax, aCause);
if (vars[n].isInstantiated() && nbMin != nbMax) {
if (vars[n].getValue() == nbMax) {
for (int i = possibleLoops.getFirstElement(); i >= 0; i = possibleLoops.getNextElement()) {
vars[i].instantiateTo(i + offSet, aCause);
assert vars[i].isInstantiatedTo(i + offSet);
nbMinLoops.add(1);
}
possibleLoops.clear();
setPassive();
} else if (vars[n].getValue() == nbMin) {
for (int i = possibleLoops.getFirstElement(); i >= 0; i = possibleLoops.getNextElement()) {
if (vars[i].removeValue(i + offSet, aCause)) {
possibleLoops.remove(i);
}
}
if (possibleLoops.isEmpty()) {
setPassive();
}
}
}
}
@Override
public void propagate(int idV, int mask) throws ContradictionException {
if (idV < n) {
if (possibleLoops.contain(idV)) {
if (vars[idV].contains(idV + offSet)) {
if (vars[idV].isInstantiated()) {
nbMinLoops.add(1);
possibleLoops.remove(idV);
}
} else {
possibleLoops.remove(idV);
}
}
}
filter();
}
@Override
public ESat isEntailed() {
int nbMax = 0;
int nbMin = 0;
for (int i = 0; i < n; i++) {
if (vars[i].contains(i + offSet)) {
nbMax++;
if (vars[i].isInstantiated()) {
nbMin++;
}
}
}
if (vars[n].getLB() > nbMax || vars[n].getUB() < nbMin) {
return ESat.FALSE;
}
if (nbMin == nbMax && vars[n].isInstantiated()) {
return ESat.TRUE;
}
return ESat.UNDEFINED;
}
@Override
public void duplicate(Solver solver, THashMap<Object, Object> identitymap) {
if (!identitymap.containsKey(this)) {
int size = this.vars.length - 1;
IntVar[] aVars = new IntVar[size];
for (int i = 0; i < size; i++) {
this.vars[i].duplicate(solver, identitymap);
aVars[i] = (IntVar) identitymap.get(this.vars[i]);
}
this.vars[size].duplicate(solver, identitymap);
IntVar aVar = (IntVar) identitymap.get(this.vars[size]);
identitymap.put(this, new PropKLoops(aVars, this.offSet, aVar));
}
}
}