/* Check if we reached a fixpoint. That is, if there are no states in <largeSet>
* which are absent from <smallSet>.
*/
private bool IsFixpoint(FormulaNode largeSet, FormulaNode smallSet, SymbolicState v)
{
FormulaNode notNew = new FormulaNode(LogicOperator.NOT, smallSet, null);
FormulaNode stateRemoved = new FormulaNode(LogicOperator.AND, largeSet, notNew);
stateRemoved = v.Quantify(LogicOperator.EXISTS, stateRemoved);
return(!FormulaCNF.QBFSAT(stateRemoved));
}
public bool Check()
{
SymbolicState v = new SymbolicState(elementary, "v");
// initially, all possible states belong to the structure
FormulaNode states = new FormulaNode(FormulaNode.TRUE_LITERAL);
FormulaNode oldStates;
while (true)
{
iterations++;
#if DEBUG
Console.WriteLine("Iteration " + iterations.ToString());
#endif
oldStates = states;
FormulaNode succ = GenSucc(states, v);
FormulaNode lc1 = GenLC1(states, v);
FormulaNode e = GenE(states, v);
FormulaNode a = GenA(states, v);
states = new FormulaNode(LogicOperator.AND, states, succ);
states = new FormulaNode(LogicOperator.AND, states, lc1);
states = new FormulaNode(LogicOperator.AND, states, e);
states = new FormulaNode(LogicOperator.AND, states, a);
if (IsFixpoint(oldStates, states, v))
{
break;
}
}
#if DEBUG
Console.WriteLine("Reached fixpoint. Checking for satisfying state");
#endif
FormulaNode formulaValue = v.ValueOf(normalized);
FormulaNode formulaAndValid = new FormulaNode(LogicOperator.AND, states, formulaValue);
FormulaNode sat = v.Quantify(LogicOperator.EXISTS, formulaAndValid);
return(FormulaCNF.QBFSAT(sat));
}