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package solver.constraints.ternary;
import gnu.trove.map.hash.THashMap;
import solver.Solver;
import solver.constraints.Propagator;
import solver.constraints.PropagatorPriority;
import solver.exception.ContradictionException;
import solver.variables.IntVar;
import solver.variables.events.IntEventType;
import util.ESat;
/**
* X = MAX(Y,Z)
* <br/>
* ensures bound consistency
*
* @author Charles Prud'homme
* @since 19/04/11
*/
public class PropMaxBC extends Propagator<IntVar> {
IntVar MAX, v1, v2;
public PropMaxBC(IntVar X, IntVar Y, IntVar Z) {
super(new IntVar[]{X, Y, Z}, PropagatorPriority.TERNARY, true);
this.MAX = vars[0];
this.v1 = vars[1];
this.v2 = vars[2];
}
@Override
public int getPropagationConditions(int vIdx) {
return IntEventType.boundAndInst();
}
@Override
public void propagate(int evtmask) throws ContradictionException {
filter();
}
@Override
public void propagate(int varIdx, int mask) throws ContradictionException {
propagate(0);
}
private void filter() throws ContradictionException {
int c = 0;
c += (vars[0].isInstantiated() ? 1 : 0);
c += (vars[1].isInstantiated() ? 2 : 0);
c += (vars[2].isInstantiated() ? 4 : 0);
switch (c) {
case 7: // everything is instantiated
case 6:// Z and Y are instantiated
vars[0].instantiateTo(Math.max(vars[1].getValue(), vars[2].getValue()), aCause);
setPassive();
break;
case 5: // X and Z are instantiated
{
int max = vars[0].getValue();
int val2 = vars[2].getValue();
if (max > val2) {
vars[1].instantiateTo(max, aCause);
setPassive();
} else if (max < val2) {
contradiction(vars[2], "wrong max selected");
} else { // X = Z
vars[1].updateUpperBound(max, aCause);
}
}
break;
case 4: // Z is instantiated
{
int val = vars[2].getValue();
if (val > vars[1].getUB()) { // => X = Z
vars[0].instantiateTo(val, aCause);
setPassive();
} else {
_filter();
}
}
break;
case 3:// X and Y are instantiated
{
int max = vars[0].getValue();
int val1 = vars[1].getValue();
if (max > val1) {
vars[2].instantiateTo(max, aCause);
setPassive();
} else if (max < val1) {
contradiction(vars[1], "");
} else { // X = Y
vars[2].updateUpperBound(max, aCause);
}
}
break;
case 2: // Y is instantiated
{
int val = vars[1].getValue();
if (val > vars[2].getUB()) { // => X = Y
vars[0].instantiateTo(val, aCause);
setPassive();
} else { // val in Z
_filter();
}
}
break;
case 1: // X is instantiated
{
int max = vars[0].getValue();
if (!vars[1].contains(max) && !vars[2].contains(max)) {
contradiction(vars[0], null);
}
if (vars[1].getUB() < max) {
vars[2].instantiateTo(max, aCause);
setPassive();
} else if (vars[2].getUB() < max) {
vars[1].instantiateTo(max, aCause);
setPassive();
} else {
if (vars[1].updateUpperBound(max, aCause) | vars[2].updateUpperBound(max, aCause)) {
filter(); // to ensure idempotency for "free"
}
}
}
break;
case 0: // otherwise
_filter();
break;
}
}
private void _filter() throws ContradictionException {
boolean change;
do {
change = vars[0].updateLowerBound(Math.max(vars[1].getLB(), vars[2].getLB()), aCause);
change |= vars[0].updateUpperBound(Math.max(vars[1].getUB(), vars[2].getUB()), aCause);
change |= vars[1].updateUpperBound(vars[0].getUB(), aCause);
change |= vars[2].updateUpperBound(vars[0].getUB(), aCause);
if (vars[2].getUB() < vars[0].getLB()) {
change |= vars[1].updateLowerBound(vars[0].getLB(), aCause);
}
if (vars[1].getUB() < vars[0].getLB()) {
change |= vars[2].updateLowerBound(vars[0].getLB(), aCause);
}
} while (change);
}
@Override
public ESat isEntailed() {
if (isCompletelyInstantiated()) {
if (MAX.getValue() != Math.max(v1.getValue(), v2.getValue())) {
return ESat.FALSE;
} else {
return ESat.TRUE;
}
}
return ESat.UNDEFINED;
}
@Override
public String toString() {
return MAX.toString() + ".MAX(" + v1.toString() + "," + v2.toString() + ")";
}
@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]);
this.vars[2].duplicate(solver, identitymap);
IntVar Z = (IntVar) identitymap.get(this.vars[2]);
identitymap.put(this, new PropMaxBC(X, Y, Z));
}
}
}