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* Copyright (c) 1999-2014, Ecole des Mines de Nantes
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* modification, are permitted provided that the following conditions are met:
*
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* documentation and/or other materials provided with the distribution.
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* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
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/**
* Created by IntelliJ IDEA.
* User: Jean-Guillaume Fages
* Date: 16/11/11
* Time: 10:42
*/
package solver.constraints.nary.circuit;
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.PropagatorEventType;
import util.ESat;
import util.graphOperations.connectivity.StrongConnectivityFinder;
import util.objects.graphs.DirectedGraph;
import util.objects.setDataStructures.ISet;
import util.objects.setDataStructures.SetFactory;
import util.objects.setDataStructures.SetType;
import java.util.BitSet;
import java.util.Random;
/**
* Filters subcircuit based on strongly connected components
*
* @author Jean-Guillaume Fages
*/
public class PropSubCircuitSCC extends Propagator<IntVar> {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
private int n, n2;
private DirectedGraph support;
private StrongConnectivityFinder SCCfinder;
private DirectedGraph G_R;
private int[] sccOf;
private ISet[] mates;
// proba
private Random rd;
private int offSet;
private BitSet mandSCC;
private int[] possibleSources;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
public PropSubCircuitSCC(IntVar[] succs, int offSet) {
super(succs, PropagatorPriority.LINEAR, false);
this.offSet = offSet;
n = vars.length;
n2 = n + 1;
support = new DirectedGraph(n2, SetType.LINKED_LIST, true);
G_R = new DirectedGraph(n2, SetType.LINKED_LIST, false);
SCCfinder = new StrongConnectivityFinder(support);
mates = new ISet[n2];
for (int i = 0; i < n2; i++) {
mates[i] = SetFactory.makeLinkedList(false);
}
rd = new Random(0);
mandSCC = new BitSet(n2);
possibleSources = new int[n];
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public ESat isEntailed() {
return ESat.TRUE;// redundant propagator
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (PropagatorEventType.isFullPropagation(evtmask)) {
for (int i = 0; i < n; i++) {
vars[i].updateLowerBound(offSet, aCause);
vars[i].updateUpperBound(n - 1 + offSet, aCause);
}
}
int size = 0;
for (int i = 0; i < n; i++) {
if (!vars[i].contains(i + offSet)) {
possibleSources[size++] = i;
}
}
if (size > 0) {
filterFromSource(possibleSources[rd.nextInt(size)]);
}
}
public void filterFromSource(int source) throws ContradictionException {
assert (!vars[source].contains(source+offSet));
// reset data structures
rebuild(source);
int first = sccOf[source];
int last = sccOf[n];
int n_R = SCCfinder.getNbSCC();
// forces variables that cannot connect source to n, to be loops
for(int i=0;i<n_R;i++){
if(i!=first && G_R.getPredOf(i).isEmpty()){
makeLoops(source,i,false);
}
else if(i!=last && G_R.getSuccOf(i).isEmpty()){
makeLoops(source,i,true);
}
}
// additional filter (based on instantiated arcs)
filterFromInst(source);
// ad hoc filtering rules
checkSCCLink();
}
public void rebuild(int source) {
mandSCC.clear();
for(int i=0;i<n2;i++){
mates[i].clear();
support.getSuccOf(i).clear();
support.getPredOf(i).clear();
G_R.getPredOf(i).clear();
G_R.getSuccOf(i).clear();
}
G_R.getNodes().clear();
for(int i=0;i<n;i++){
IntVar v = vars[i];
int lb = v.getLB();
int ub = v.getUB();
for(int j=lb;j<=ub;j=v.nextValue(j)){
if(j-offSet==source){
support.addArc(i,n);
}else{
support.addArc(i,j-offSet);
}
}
}
SCCfinder.findAllSCC();
int n_R = SCCfinder.getNbSCC();
for (int i = 0; i < n_R; i++) {
G_R.getNodes().add(i);
}
sccOf = SCCfinder.getNodesSCC();
ISet succs;
int x;
for (int i = 0; i < n; i++) {
x = sccOf[i];
if(!vars[i].contains(i+offSet)){
mandSCC.set(x);
}
succs = support.getSuccOf(i);
for (int j = succs.getFirstElement(); j >= 0; j = succs.getNextElement()) {
if (x != sccOf[j]) {
G_R.addArc(x, sccOf[j]);
mates[x].add((i + 1) * n2 + j);
}
}
}
}
private void makeLoops(int source, int cc, boolean sink) throws ContradictionException {
if (cc == sccOf[source]) {
if (sink) {
contradiction(vars[0], "");
} else {
return;
}
}
if (cc == sccOf[n]) {
if (sink) {
return;
} else {
contradiction(vars[0], "");
}
}
// if((sink && cc==sccOf[source]) || (cc==sccOf[n] && !sink)){
// contradiction(vars[0],"");
// }
for(int i=SCCfinder.getSCCFirstNode(cc); i>=0; i=SCCfinder.getNextNode(i)){
vars[i].instantiateTo(i+offSet,aCause);
}
mates[cc].clear();
if(sink){
ISet ps = G_R.getPredOf(cc);
for(int p=ps.getFirstElement();p>=0;p=ps.getNextElement()){
G_R.removeArc(p,cc);
if(G_R.getSuccOf(p).isEmpty()){
makeLoops(source,p,sink);
}
}
}else{
ISet ss = G_R.getSuccOf(cc);
for(int s=ss.getFirstElement();s>=0;s=ss.getNextElement()){
G_R.removeArc(cc,s);
if(G_R.getPredOf(s).isEmpty()){
makeLoops(source,s,sink);
}
}
}
}
private void filterFromInst(int source) throws ContradictionException {
int to, arc, x;
for (int i = 0; i < n; i++) {
if (vars[i].isInstantiated()) {
to = vars[i].getValue() - offSet;
x = sccOf[i];
if (to == source) {
to = n;
}
if (to != -1 && sccOf[to] != x && mates[x].getSize() > 1) {
arc = (i + 1) * n2 + to;
for (int a = mates[x].getFirstElement(); a >= 0; a = mates[x].getNextElement()) {
if (a != arc) {
int val = a % n2;
if (val == n) {
val = source;
}
vars[a / n2 - 1].removeValue(val + offSet, aCause);
}
}
mates[x].clear();
mates[x].add(arc);
}
}
}
}
private void checkSCCLink() throws ContradictionException {
for (int sccFrom=G_R.getNodes().getFirstElement(); sccFrom>=0; sccFrom=G_R.getNodes().getNextElement()) {
int door = -1;
for (int i = mates[sccFrom].getFirstElement(); i >= 0; i = mates[sccFrom].getNextElement()) {
if(door == -1){
door = i/n2-1;
}else if(door!=i/n2-1){
return;
}
}
if(door>=0){
int lb = vars[door].getLB();
int ub = vars[door].getUB();
for(int v=lb;v<=ub;v=vars[door].nextValue(v)){
if(sccOf[v-offSet]==sccFrom){
if(v-offSet!=door || mandSCC.get(sccFrom)){
vars[door].removeValue(v,aCause);
}
}
}
}
}
}
@Override
public void duplicate(Solver solver, THashMap<Object, Object> identitymap) {
if (!identitymap.containsKey(this)) {
int size = this.vars.length;
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]);
}
identitymap.put(this, new PropSubCircuitSCC(aVars, this.offSet));
}
}
}