public bool dpllSatisfiable(Sentence s, Model m)
{
List<Sentence> clauses = new CNFClauseGatherer()
.getClausesFrom(new CNFTransformer().transform(s));
List<Symbol> symbols = new SymbolCollector()
.getSymbolsIn(s);
// System.Console.WriteLine(" numberOfSymbols = " + symbols.Count);
return dpll(clauses, symbols, m);
}
public void testDPLLFilteringNonTrueClausesGivesNullWhenAllClausesAreKnown()
{
Model model = new Model();
model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
true).extend(new Symbol("C"), true);
Sentence sentence = (Sentence)parser
.parse("((A AND B) AND (B AND C))");
List<Sentence> clauseList = new CNFClauseGatherer()
.getClausesFrom(new CNFTransformer()
.transform(sentence));
List<Sentence> clausesWithNonTrueValues = dpll
.clausesWithNonTrueValues(clauseList, model);
Assert.AreEqual(0, clausesWithNonTrueValues.Count);
}
public void testDPLLFiltersClausesTheStatusOfWhichAreKnown()
{
Model model = new Model();
model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
true);
Sentence sentence = (Sentence)parser
.parse("((A AND B) AND (B AND C))");
List<Sentence> clauseList = new CNFClauseGatherer()
.getClausesFrom(new CNFTransformer()
.transform(sentence));
List<Sentence> clausesWithNonTrueValues = dpll
.clausesWithNonTrueValues(clauseList, model);
Assert.AreEqual(1, clausesWithNonTrueValues.Count);
Sentence nonTrueClause = (Sentence)parser.parse("(B AND C)");
clausesWithNonTrueValues.Contains(nonTrueClause);
}
public Model findModelFor(String logicalSentence, int numberOfFlips,
double probabilityOfRandomWalk)
{
myModel = new Model();
Sentence s = (Sentence)new PEParser().parse(logicalSentence);
CNFTransformer transformer = new CNFTransformer();
CNFClauseGatherer clauseGatherer = new CNFClauseGatherer();
SymbolCollector sc = new SymbolCollector();
List<Symbol> symbols = sc.getSymbolsIn(s);
Random r = new Random();
for (int i = 0; i < symbols.Count; i++)
{
Symbol sym = (Symbol)symbols[i];
myModel = myModel.extend(sym, Util.randombool());
}
List<Sentence> clauses = clauseGatherer.getClausesFrom(transformer
.transform(s));
for (int i = 0; i < numberOfFlips; i++)
{
if (getNumberOfClausesSatisfiedIn(clauses, myModel) == clauses.Count)
{
return myModel;
}
Sentence clause = clauses[random.Next(clauses.Count)];
List<Symbol> symbolsInClause = sc
.getSymbolsIn(clause);
if (random.NextDouble() >= probabilityOfRandomWalk)
{
Symbol randomSymbol = symbolsInClause[random
.Next(symbolsInClause.Count)];
myModel = myModel.flip(randomSymbol);
}
else
{
Symbol symbolToFlip = getSymbolWhoseFlipMaximisesSatisfiedClauses(
clauses,
symbolsInClause, myModel);
myModel = myModel.flip(symbolToFlip);
}
}
return null;
}
public bool plResolution(KnowledgeBase kb, Sentence alpha)
{
Sentence kBAndNotAlpha = new BinarySentence("AND", kb.asSentence(),
new UnarySentence(alpha));
List<Sentence> clauses = new CNFClauseGatherer()
.getClausesFrom(new CNFTransformer().transform(kBAndNotAlpha));
clauses = filterOutClausesWithTwoComplementaryLiterals(clauses);
List<Sentence> newClauses = new List<Sentence>();
while (true)
{
List<List<Sentence>> pairs = getCombinationPairs(clauses);
for (int i = 0; i < pairs.Count; i++)
{
List<Sentence> pair = pairs[i];
// System.Console.WriteLine("pair number" + i+" of "+pairs.Count);
List<Sentence> resolvents = plResolve(pair[0], pair[1]);
resolvents = filterOutClausesWithTwoComplementaryLiterals(resolvents);
if (resolvents.Contains(new Symbol("EMPTY_CLAUSE")))
{
return true;
}
newClauses = SetOps.union(newClauses, resolvents);
// System.Console.WriteLine("clauseslist size = " +clauses.Count);
}
if (SetOps.intersection(newClauses, clauses).Count == newClauses
.Count)
{// subset test
return false;
}
clauses = SetOps.union(newClauses, clauses);
clauses = filterOutClausesWithTwoComplementaryLiterals(clauses);
}
}
public void setUp()
{
parser = new PEParser();
gatherer = new CNFClauseGatherer();
}
public void testDPLLFindsPurePositiveSymbolsWhenTheyExist()
{
Model model = new Model();
model = model.extend(new Symbol("A"), true).extend(new Symbol("B"),
true);
Sentence sentence = (Sentence)parser
.parse("((A AND B) AND (B AND C))");
List<Sentence> clauseList = new CNFClauseGatherer()
.getClausesFrom(new CNFTransformer()
.transform(sentence));
List<Symbol> symbolList = new SymbolCollector().getSymbolsIn(sentence);
DPLL.SymbolValuePair sv = dpll.findPureSymbolValuePair(clauseList,
model, symbolList);
Assert.IsNotNull(sv);
Assert.AreEqual(new Symbol("C"), sv.symbol);
Assert.AreEqual(true, sv.value);
}
