/**
* Add a copy of the current decision to path
*
* @param dec a decision of the current decision path
*/
private void addToPath(Decision dec) {
Decision clone = dec.duplicate();
path.add(clone);
int pos = path.size() - 1;
if (!dec.hasNext()) {
refuted.set(pos);
}
/*boolean forceNext = !dec.hasNext();
if (forceNext) {
clone.buildNext(); // force to set up the decision in the very state it was
clone.buildNext(); // that's why we call it twice
}*/
}
/** Compute the initial fragment, ie set of decisions to keep. */
private void clonePath() {
Decision dec = mSolver.getSearchLoop().getLastDecision();
while ((dec != RootDecision.ROOT)) {
addToPath(dec);
dec = dec.getPrevious();
}
Collections.reverse(path);
int size = path.size();
for (int i = 0, mid = size >> 1, j = size - 1; i < mid; i++, j--) {
boolean bi = refuted.get(i);
refuted.set(i, refuted.get(j));
refuted.set(j, bi);
}
}
/**
* Copy the current decision path in _unkopen, for comparison with copen. Then, it compares each
* decision, from the top to the bottom, to find the first difference. This is required to avoid
* adding the same decision sub-path more than once
*
* @param searchLoop the search loop
* @return the index of the decision, in _unkopen, that stops the loop
*/
private int compareSubpath(SearchLoop searchLoop) {
_unkopen.clear();
Decision decision = searchLoop.decision;
while (decision != topDecision) {
_unkopen.add(decision);
decision = decision.getPrevious();
}
Collections.reverse(_unkopen);
//
int i = 0;
int I = Math.min(_unkopen.size(), copen.length);
while (i < I && copen[i].isEquivalentTo(_unkopen.get(i))) {
i++;
}
return i;
}
@Override
public void afterUpBranch() {
// we need to catch up that case when the sub tree is closed and this imposes a fragment
if (last != null && mSolver.getSearchLoop().getLastDecision().getId() == last.getId()) {
mSolver.getSearchLoop().restart();
}
}
/**
* Extract the open right branches from the current path until it reaches the i^th decision of
* _unkopen
*
* @param searchLoop the search loop
* @param i the index of the decision, in _unkopen, that stops the loop
*/
private void extractOB(SearchLoop searchLoop, int i) {
Decision stopAt = _unkopen.get(i).getPrevious();
// then, goes up in the search tree, and detect open nodes
searchLoop.mSolver.getEnvironment().worldPop();
Decision decision = searchLoop.decision;
int bound;
while (decision != stopAt) {
bound =
isMinimization
? objectiveManager.getObjective().getLB()
: objectiveManager.getObjective().getUB();
if (decision.hasNext() && isValid(bound)) {
opens.add(new Open(decision, bound, isMinimization));
}
searchLoop.decision = searchLoop.decision.getPrevious();
decision.free();
decision = searchLoop.decision;
searchLoop.mSolver.getEnvironment().worldPop();
}
}
@Override
public void fixSomeVariables(ICause cause) throws ContradictionException {
// this is called after restart
// if required, force the cut and explain the cut
if (forceCft) {
explainCut();
nbFixedVariables = related2cut.cardinality();
nbCall = 0;
increaseLimit();
}
// then fix variables
// this part is specific: a fake decision path has to be created
nbCall++;
restrictLess();
notFrozen.clear();
notFrozen.or(related2cut);
for (; !notFrozen.isEmpty() && notFrozen.cardinality() > nbFixedVariables; ) {
int idx = selectVariable();
notFrozen.clear(idx);
}
assert mSolver.getSearchLoop().getLastDecision() == RootDecision.ROOT;
// add the first refuted decisions
int first = notFrozen.nextSetBit(0);
for (int i = (first > -1 ? refuted.nextSetBit(first) : first);
i > -1;
i = refuted.nextSetBit(i + 1)) {
notFrozen.clear(i);
}
// add unrelated
notFrozen.or(unrelated);
// then build the fake decision path
last = null;
// LOGGER.debug("relax cut {}", notFrozen.cardinality());
for (int id = notFrozen.nextSetBit(0);
id >= 0 && id < path.size();
id = notFrozen.nextSetBit(id + 1)) {
// last = ExplanationToolbox.mimic(path.get(id)); // required because some
// unrelated decisions can be refuted
if (path.get(id).hasNext()) {
last = path.get(id).duplicate();
if (refuted.get(id)) last.buildNext();
ExplanationToolbox.imposeDecisionPath(mSolver, last);
}
}
}
/**
* Create an open right branch for HBFS
*
* @param decision an open decision
* @param currentBound current lower (resp. upper) bound of the objective value for mimimization
* (resp. maximization)
* @param minimization set to <tt>true</tt> for minimization
*/
public Open(Decision<IntVar> decision, int currentBound, boolean minimization) {
this.path = new ArrayList<>();
while (decision != topDecision) {
Decision d = decision.duplicate();
while (decision.triesLeft() != d.triesLeft() - 1) {
d.buildNext();
}
path.add(d);
decision = decision.getPrevious();
}
this.currentBound = currentBound;
this.minimization = (byte) (minimization ? 1 : -1);
}
/** Force the failure, apply decisions to the last solution + cut => failure! */
private void explainCut() {
// Goal: force the failure to get the set of decisions related to the cut
forceCft = false;
// 1. make a backup
mSolver.getEnvironment().worldPush();
Decision d;
try {
Decision previous = mSolver.getSearchLoop().getLastDecision();
assert previous == RootDecision.ROOT;
// 2. apply the decisions
mExplanationEngine.getSolver().getObjectiveManager().postDynamicCut();
for (int i = 0; i < path.size(); i++) {
d = path.get(i);
d.setPrevious(previous);
d.buildNext();
if (refuted.get(i)) d.buildNext();
d.apply();
mSolver.propagate();
previous = d;
}
// mSolver.propagate();
assert false : "SHOULD FAIL!";
} catch (ContradictionException cex) {
if ((cex.v != null) || (cex.c != null)) { // contradiction on domain wipe out
tmpDeductions.clear();
tmpValueDeductions.clear();
related2cut.clear();
unrelated.clear();
// 3. explain the failure
Explanation expl = new Explanation();
if (cex.v != null) {
cex.v.explain(mExplanationEngine, VariableState.DOM, expl);
} else {
cex.c.explain(mExplanationEngine, null, expl);
}
Explanation complete = mExplanationEngine.flatten(expl);
ExplanationToolbox.extractDecision(complete, tmpValueDeductions);
tmpDeductions.addAll(tmpValueDeductions);
if (tmpDeductions.isEmpty()) {
// if (LOGGER.isErrorEnabled()) {
// LOGGER.error("2 cases: (a) optimality proven or (b) bug in
// explanation");
// }
// throw new SolverException("2 cases: (a) optimality proven or (b) bug
// in explanation");
isTerminated = true;
}
for (int i = 0; i < tmpDeductions.size(); i++) {
int idx = path.indexOf(((BranchingDecision) tmpDeductions.get(i)).getDecision());
related2cut.set(idx);
}
// 4. need to replace the duplicated decision with the correct one
for (int i = 0; i < path.size(); i++) {
Decision dec = path.get(i);
boolean forceNext = !dec.hasNext();
dec.rewind();
if (forceNext) dec.buildNext();
dec.setPrevious(null); // useless .. but ... you know
}
} else {
throw new UnsupportedOperationException(
this.getClass().getName() + ".onContradiction incoherent state");
}
}
mSolver.getEnvironment().worldPop();
mSolver.getEngine().flush();
unrelated.andNot(related2cut);
unrelated.andNot(refuted);
}
