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 bool ttEntails(KnowledgeBase kb, String alpha)
{
Sentence kbSentence = kb.asSentence();
Sentence querySentence = (Sentence)new PEParser().parse(alpha);
SymbolCollector collector = new SymbolCollector();
List<Symbol> kbSymbols = collector.getSymbolsIn(kbSentence);
List<Symbol> querySymbols = collector.getSymbolsIn(querySentence);
List<Symbol> symbols = SetOps.union(kbSymbols, querySymbols);
List<Symbol> symbolList = symbols;
return ttCheckAll(kbSentence, querySentence, symbolList, new Model());
}
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 void setUp()
{
parser = new PEParser();
collector = new SymbolCollector();
}
public HornClause(Sentence sentence, PLFCEntails plfcEntails)
{
this.plfcEntails = plfcEntails;
if (sentence is Symbol)
{
_head = (Symbol)sentence;
plfcEntails.agenda.Push(_head);
premiseSymbols = new List<Symbol>();
plfcEntails.count.Add(this, 0);
plfcEntails._inferred.Add(_head, false);
}
else if (!isImpliedSentence(sentence))
{
throw new ApplicationException("Sentence " + sentence
+ " is not a horn clause");
}
else
{
BinarySentence bs = (BinarySentence)sentence;
_head = (Symbol)bs.getSecond();
if (plfcEntails._inferred.ContainsKey(_head))
{
plfcEntails._inferred[_head] = false;
}
else
{
plfcEntails._inferred.Add(_head, false);
}
List<Symbol> symbolsInPremise = new SymbolCollector()
.getSymbolsIn(bs.getFirst());
foreach(Symbol s in symbolsInPremise)
{
plfcEntails._inferred.Add(s, false);
}
premiseSymbols = symbolsInPremise;
plfcEntails.count.Add(this, premiseSymbols.Count);
}
}
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);
}
