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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;
/**
* V0 * V1 = V2
* <br/>
*
* @author Charles Prud'homme
* @since 26/01/11
*/
public class PropTimesNaive extends Propagator<IntVar> {
protected static final int MAX = Integer.MAX_VALUE - 1, MIN = Integer.MIN_VALUE + 1;
IntVar v0, v1, v2;
public PropTimesNaive(IntVar v1, IntVar v2, IntVar result) {
super(new IntVar[]{v1, v2, result}, PropagatorPriority.TERNARY, false);
this.v0 = vars[0];
this.v1 = vars[1];
this.v2 = vars[2];
}
@Override
public final int getPropagationConditions(int vIdx) {
return IntEventType.boundAndInst();
}
@Override
public final void propagate(int evtmask) throws ContradictionException {
boolean hasChanged = true;
while (hasChanged) {
hasChanged = div(v0, v2.getLB(), v2.getUB(), v1.getLB(), v1.getUB());
hasChanged |= div(v1, v2.getLB(), v2.getUB(), v0.getLB(), v0.getUB());
hasChanged |= mul(v2, v0.getLB(), v0.getUB(), v1.getLB(), v1.getUB());
}
if (v2.isInstantiatedTo(0) && (v0.isInstantiatedTo(0) || v1.isInstantiatedTo(1))) {
setPassive();
}
}
@Override
public final ESat isEntailed() {
if (isCompletelyInstantiated()) {
return ESat.eval(v0.getValue() * v1.getValue() == v2.getValue());
}
return ESat.UNDEFINED;
}
@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 PropTimesNaive(X, Y, Z));
}
}
private boolean div(IntVar var, int a, int b, int c, int d) throws ContradictionException {
int min = 0, max = 0;
if (a <= 0 && b >= 0 && c <= 0 && d >= 0) { // case 1
min = MIN;
max = MAX;
return var.updateLowerBound(min, this) | var.updateUpperBound(max, this);
} else if (c == 0 && d == 0 && (a > 0 || b < 0)) // case 2
this.contradiction(var, "");
else if (c < 0 && d > 0 && (a > 0 || b < 0)) { // case 3
max = Math.max(Math.abs(a), Math.abs(b));
min = -max;
return var.updateLowerBound(min, this) | var.updateUpperBound(max, this);
} else if (c == 0 && d != 0 && (a > 0 || b < 0)) // case 4 a
return div(var, a, b, 1, d);
else if (c != 0 && d == 0 && (a > 0 || b < 0)) // case 4 b
return div(var, a, b, c, -1);
else { // if (c > 0 || d < 0) { // case 5
float ac = (float) a / c, ad = (float) a / d,
bc = (float) b / c, bd = (float) b / d;
float low = Math.min(Math.min(ac, ad), Math.min(bc, bd));
float high = Math.max(Math.max(ac, ad), Math.max(bc, bd));
min = (int) Math.round(Math.ceil(low));
max = (int) Math.round(Math.floor(high));
if (min > max) this.contradiction(var, "");
return var.updateLowerBound(min, this) | var.updateUpperBound(max, this);
}
return false;
}
private boolean mul(IntVar var, int a, int b, int c, int d) throws ContradictionException {
int min = Math.min(Math.min(multiply(a, c), multiply(a, d)), Math.min(multiply(b, c), multiply(b, d)));
int max = Math.max(Math.max(multiply(a, c), multiply(a, d)), Math.max(multiply(b, c), multiply(b, d)));
return var.updateLowerBound(min, this) | var.updateUpperBound(max, this);
}
public final static int multiply(int a, int b) {
if (a == 0 || b == 0)
return 0;
int product = (int) (a * b);
int a2 = (int) (product / b);
if (a != a2)
throw new ArithmeticException("Overflow occurred from int " + a + " * " + b);
return product;
}
}