/**
* {@inheritDoc}
*
* @see kodkod.engine.satlab.ReductionStrategy#next(kodkod.engine.satlab.ResolutionTrace)
*/
public IntSet next(ResolutionTrace trace) {
if (hits.isEmpty()) return Ints.EMPTY_SET; // tried everything
final IntSet relevantVars = StrategyUtils.coreTailUnits(trace);
final long[] byRelevance = sortByRelevance(trace, relevantVars);
if (DBG) printRelevant(byRelevance);
for (int i = byRelevance.length - 1; i >= 0; i--) {
final int var = (int) byRelevance[i];
if (hits.remove(var) != null) {
// remove maxVar from the set of relevant variables
relevantVars.remove(var);
if (relevantVars.isEmpty()) break; // there was only one root formula left
// get all axioms and resolvents corresponding to the clauses that
// form the translations of formulas identified by relevant vars
final IntSet relevantClauses = clausesFor(trace, relevantVars);
assert !relevantClauses.isEmpty() && !relevantClauses.contains(trace.size() - 1);
if (DBG)
System.out.println("relevant clauses: " + relevantClauses.size() + ", removed " + var);
return relevantClauses;
}
}
hits.clear();
return Ints.EMPTY_SET;
}
/**
* Minimizes the current core using the trivial strategy that does one of the following: (1) if
* there is a root that simplified to FALSE, sets the minimal core to that root; or (2) if not,
* there must be two roots that translated to x and -x, where x is a boolean literal, so we pick
* those two as the minimal core. The strategy argument is ignored (it can be null).
*
* @see Proof#minimize(ReductionStrategy)
*/
@Override
public void minimize(ReductionStrategy strategy) {
final Map<Formula, int[]> rootLits = new LinkedHashMap<Formula, int[]>();
final Map<Formula, Node> rootNodes = new LinkedHashMap<Formula, Node>();
final Set<Formula> roots = log().roots();
for (Iterator<TranslationRecord> itr = core(); itr.hasNext(); ) {
final TranslationRecord rec = itr.next();
if (roots.contains(rec.translated())) {
// simply record the most recent output value for each formula:
// this is guaranteed to be the final output value for that
// formula because of the translation log guarantee that the
// log is replayed in the order of translation: i.e. a child's
// output value is always recorded before the parent's
int[] val = rootLits.get(rec.translated());
if (val == null) {
val = new int[1];
rootLits.put(rec.translated(), val);
}
val[0] = rec.literal();
rootNodes.put(rec.translated(), rec.node());
}
}
final SparseSequence<Formula> lits = new TreeSequence<Formula>();
for (Map.Entry<Formula, int[]> entry : rootLits.entrySet()) {
final int lit = entry.getValue()[0];
if (lit == -Integer.MAX_VALUE) {
coreRoots = Collections.singletonMap(entry.getKey(), rootNodes.get(entry.getKey()));
break;
} else if (lits.containsIndex(-lit)) {
final Formula f0 = lits.get(-lit);
final Formula f1 = entry.getKey();
coreRoots = new LinkedHashMap<Formula, Node>(3);
coreRoots.put(f0, rootNodes.get(f0));
coreRoots.put(f1, rootNodes.get(f1));
coreRoots = Collections.unmodifiableMap(coreRoots);
break;
} else {
lits.put(lit, entry.getKey());
}
}
coreFilter = null;
assert coreRoots.size() == 1
&& rootLits.get(coreRoots.keySet().iterator().next())[0] == -Integer.MAX_VALUE
|| coreRoots.size() == 2;
}
/**
* Returns a deep (modifiable) copy of this Bounds object.
*
* @return a deep (modifiable) copy of this Bounds object.
*/
public Bounds clone() {
try {
return new Bounds(
factory,
new LinkedHashMap<Relation, TupleSet>(lowers),
new LinkedHashMap<Relation, TupleSet>(uppers),
intbounds.clone());
} catch (CloneNotSupportedException cnse) {
throw new InternalError(); // should not be reached
}
}
/**
* Returns an array R of longs such that for each i, j in [0..R.length) i < j implies that the
* formula identified by (int)R[i] in this.hits contributes fewer clauses to the core of the given
* trace than the formula identified by (int)R[j].
*
* @return an array as described above
*/
private long[] sortByRelevance(ResolutionTrace trace, IntSet relevantVars) {
hits.indices().retainAll(relevantVars);
if (hits.get(hits.indices().min()) == null) { // first call, initialize the hits
for (IntIterator varItr = relevantVars.iterator(); varItr.hasNext(); ) {
final int var = varItr.next();
final IntSet varReachable = new IntBitSet(var + 1);
varReachable.add(var);
hits.put(var, varReachable);
}
for (Iterator<Clause> clauseItr = trace.reverseIterator(trace.axioms());
clauseItr.hasNext(); ) {
final Clause clause = clauseItr.next();
final int maxVar = clause.maxVariable();
for (IntSet reachableVars : hits.values()) {
if (reachableVars.contains(maxVar)) {
for (IntIterator lits = clause.literals(); lits.hasNext(); ) {
reachableVars.add(StrictMath.abs(lits.next()));
}
}
}
}
}
final long[] counts = new long[hits.size()];
for (Iterator<Clause> clauseItr = trace.iterator(trace.core()); clauseItr.hasNext(); ) {
final Clause clause = clauseItr.next();
final int maxVar = clause.maxVariable();
int i = 0;
for (IntSet reachableVars : hits.values()) {
if (reachableVars.contains(maxVar)) {
counts[i]++;
}
i++;
}
}
int i = 0;
for (IntIterator varItr = hits.indices().iterator(); varItr.hasNext(); ) {
final int var = varItr.next();
counts[i] = (counts[i] << 32) | var;
i++;
}
Arrays.sort(counts);
return counts;
}
/**
* Constructs an ARCE strategy that will use the given translation log to relate the cnf clauses
* back to the logic constraints from which they were generated.
*
* @ensures this.hardnessCutOff' = hardnessCutOff and this.recycleLimit' = recycleLimit and
* this.noRecycleRatio' = noRecycleRatio
*/
public DynamicRCEStrategy(
final TranslationLog log, double noRecycleRatio, double hardnessCutOff, double recycleLimit) {
if (noRecycleRatio < 0 || noRecycleRatio > 1)
throw new IllegalArgumentException("noRecycleRatio must be in [0..1]: " + noRecycleRatio);
if (hardnessCutOff < 1)
throw new IllegalArgumentException("hardnessCutOff must be >=1: " + hardnessCutOff);
if (recycleLimit < 1)
throw new IllegalArgumentException("recycleLimit must be >=1: " + recycleLimit);
this.noRecycleRatio = noRecycleRatio;
this.hardnessCutOff = hardnessCutOff;
this.recycleLimit = recycleLimit;
this.hits = new TreeSequence<IntSet>();
for (IntIterator itr = StrategyUtils.rootVars(log).iterator(); itr.hasNext(); ) {
hits.put(itr.next(), null);
}
}
/**
* Makes the specified tupleset an exact bound on the relational value that corresponds to the
* given integer.
*
* @requires ibound.arity = 1 && i.bound.size() = 1
* @ensures this.intBound' = this.intBound' ++ i -> ibound
* @throws NullPointerException ibound = null
* @throws IllegalArgumentException ibound.arity != 1 || ibound.size() != 1
* @throws IllegalArgumentException ibound.universe != this.universe
*/
public void boundExactly(int i, TupleSet ibound) {
checkBound(1, ibound);
if (ibound.size() != 1) throw new IllegalArgumentException("ibound.size != 1: " + ibound);
intbounds.put(i, ibound.clone().unmodifiableView());
}
/**
* Returns the set of tuples representing the given integer. If i is not mapped by this, null is
* returned.
*
* @return this.intBound[i]
*/
public TupleSet exactBound(int i) {
return intbounds.get(i);
}
/**
* Returns the set of all integers bound by this Bounds. The returned set does not support the add
* operation. It supports removal iff this is not an unmodifiable Bounds.
*
* @return this.intBounds.TupleSet
*/
public IntSet ints() {
return intbounds.indices();
}