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*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
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package solver.constraints.nary.nValue.amnv.rules;
import solver.Solver;
import solver.constraints.Propagator;
import solver.constraints.nary.nValue.amnv.mis.F;
import solver.exception.ContradictionException;
import solver.variables.IntVar;
import util.objects.graphs.UndirectedGraph;
import util.objects.setDataStructures.ISet;
import util.objects.setDataStructures.SetFactory;
import util.objects.setDataStructures.SetType;
import java.util.BitSet;
/**
* R3 filtering rule (back-propagation)
*
* @since 01/01/2014
* @author Jean-Guillaume Fages
*/
public class R3 implements R {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private int n;
private int[] valToRem;
private ISet[] learntEqualities;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
public R3(int nbDecVars, Solver solver){
n = nbDecVars;
valToRem = new int[31];
learntEqualities = new ISet[n];
for(int i=0;i<n;i++){
learntEqualities[i] = SetFactory.makeStoredSet(SetType.BITSET,n,solver);
}
}
//***********************************************************************************
// METHODS
//***********************************************************************************
public void filter(IntVar[] vars, UndirectedGraph graph, F heur, Propagator aCause) throws ContradictionException{
assert n == vars.length-1;
BitSet mis = heur.getMIS();
if(mis.cardinality()==vars[n].getUB()){
ISet nei;
for (int i = mis.nextClearBit(0); i>=0 && i < n; i = mis.nextClearBit(i + 1)) {
int mate = -1;
int last = 0;
if(valToRem.length<vars[i].getDomainSize()){
valToRem = new int[vars[i].getDomainSize()*2];
}
int ub = vars[i].getUB();
int lb = vars[i].getLB();
for (int k = lb; k <= ub; k = vars[i].nextValue(k)) {
valToRem[last++] = k;
}
nei = graph.getNeighOf(i);
for (int j = nei.getFirstElement(); j >= 0; j = nei.getNextElement()) {
if (mis.get(j)) {
if (mate == -1) {
mate = j;
} else if (mate >= 0) {
mate = -2;
}
for (int ik = 0; ik < last; ik++) {
if (vars[j].contains(valToRem[ik])) {
last--;
if (ik < last) {
valToRem[ik] = valToRem[last];
ik--;
}
}
}
if(mate==-2 && last==0)break;
}
}
if (mate >= 0) {
enforceEq(i, mate, vars, aCause);
} else {
for (int ik = 0; ik < last; ik++) {
vars[i].removeValue(valToRem[ik], aCause);
}
}
}
}
for(int i=0;i<n;i++){
for (int j = learntEqualities[i].getFirstElement(); j >= 0; j = learntEqualities[i].getNextElement()) {
enforceEq(i, j, vars, aCause);
}
}
}
protected void enforceEq(int i, int j, IntVar[] vars, Propagator aCause) throws ContradictionException {
if (i > j) {
enforceEq(j, i, vars, aCause);
} else {
learntEqualities[i].add(j);
learntEqualities[j].add(i);
IntVar x = vars[i];
IntVar y = vars[j];
while (x.getLB() != y.getLB() || x.getUB() != y.getUB()) {
x.updateLowerBound(y.getLB(), aCause);
x.updateUpperBound(y.getUB(), aCause);
y.updateLowerBound(x.getLB(), aCause);
y.updateUpperBound(x.getUB(), aCause);
}
if (x.hasEnumeratedDomain() && y.hasEnumeratedDomain()) {
int ub = x.getUB();
for (int val = x.getLB(); val <= ub; val = x.nextValue(val)) {
if (!y.contains(val)) {
x.removeValue(val, aCause);
}
}
ub = y.getUB();
for (int val = y.getLB(); val <= ub; val = y.nextValue(val)) {
if (!x.contains(val)) {
y.removeValue(val, aCause);
}
}
}
}
}
}