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package solver.constraints.binary;
import gnu.trove.map.hash.THashMap;
import solver.Solver;
import solver.constraints.Propagator;
import solver.constraints.PropagatorPriority;
import solver.exception.ContradictionException;
import solver.explanations.Deduction;
import solver.explanations.Explanation;
import solver.explanations.VariableState;
import solver.variables.IntVar;
import solver.variables.Variable;
import solver.variables.events.IntEventType;
import util.ESat;
/**
* A specific <code>Propagator</code> extension defining filtering algorithm for:
* <br/>
* <b>X + Y =/= C</b>
* <br>where <i>X</i> and <i>Y</i> are <code>Variable</code> objects and <i>C</i> a constant.
* <br>
* This <code>Propagator</code> defines the <code>propagate</code> and <code>awakeOnInst</code> methods. The other ones
* throw <code>UnsupportedOperationException</code>.
* <br/>
* <br/>
* <i>Based on Choco-2.1.1</i>
*
* @author Xavier Lorca
* @author Charles Prud'homme
* @author Arnaud Malapert
* @version 0.01, june 2010
* @since 0.01
*/
public class PropNotEqualXY_C extends Propagator<IntVar> {
IntVar x;
IntVar y;
int cste;
@SuppressWarnings({"unchecked"})
public PropNotEqualXY_C(IntVar[] vars, int c) {
super(vars, PropagatorPriority.BINARY, true);
this.x = vars[0];
this.y = vars[1];
this.cste = c;
}
@Override
public int getPropagationConditions(int vIdx) {
if (vars[vIdx].hasEnumeratedDomain()) {
return IntEventType.instantiation();
}
return IntEventType.boundAndInst();
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (x.isInstantiated()) {
removeValV1();
} else if (y.isInstantiated()) {
removeValV0();
} else if (x.getLB() + y.getLB() > cste || x.getUB() + y.getUB() < cste) {
setPassive();
}
}
@Override
public void propagate(int varIdx, int mask) throws ContradictionException {
propagate(0);
}
private void removeValV0() throws ContradictionException {
if (x.removeValue(cste - y.getValue(), aCause)
|| !x.contains(cste - y.getValue())) {
this.setPassive();
}
}
private void removeValV1() throws ContradictionException {
if (y.removeValue(cste - x.getValue(), aCause)
|| !y.contains(cste - x.getValue())) {
this.setPassive();
}
}
@Override
public ESat isEntailed() {
if ((x.getUB() + y.getUB() < cste) ||
(y.getLB() + x.getLB() > cste))
return ESat.TRUE;
else if (x.isInstantiated()
&& y.isInstantiated()
&& x.getValue() + y.getValue() == this.cste)
return ESat.FALSE;
else
return ESat.UNDEFINED;
}
@Override
public void explain(Deduction d, Explanation e) {
e.add(solver.getExplainer().getPropagatorActivation(this));
Variable var = d.getVar();
if (var.equals(x)) {
// a deduction has been made on x ; this is related to y only
y.explain(VariableState.DOM, e);
} else if (var != null) {
x.explain(VariableState.DOM, e);
}
// and the application of the current propagator
e.add(aCause);
}
@Override
public void duplicate(Solver solver, THashMap<Object, Object> identitymap) {
if (!identitymap.containsKey(this)) {
this.vars[0].duplicate(solver, identitymap);
IntVar X = (IntVar) identitymap.get(this.vars[0]);
this.vars[1].duplicate(solver, identitymap);
IntVar Y = (IntVar) identitymap.get(this.vars[1]);
identitymap.put(this, new PropNotEqualXY_C(new IntVar[]{X, Y}, this.cste));
}
}
}