/// <summary>
/// Computes the ratio of the symmetric difference to the size of dfa1 enumerating paths up to length n (uses the complement if density is high)
/// </summary>
/// <returns>size of ((dfa2-dfa1)+(dfa1-dfa2))/dfa1</returns>
public static double GetDFADifferenceRatio(Automaton <BDD> dfa1, Automaton <BDD> dfa2, HashSet <char> al, CharSetSolver solver)
{
var solutionDensity = DFADensity.GetDFADensity(dfa1, al, solver);
//Symmetric difference
var dfadiff1 = dfa1.Minus(dfa2, solver);
var dfadiff2 = dfa2.Minus(dfa1, solver);
var dfatrue = Automaton <BDD> .Create(0, new int[] { 0 }, new Move <BDD>[] { new Move <BDD>(0, 0, solver.True) });
var dfadiff = dfatrue.Minus(dfatrue.Minus(dfadiff1, solver).Intersect(dfatrue.Minus(dfadiff2, solver), solver), solver).Determinize(solver).Minimize(solver);
//Use smallest of |dfa1| and complement of |dfa1| for cardinality base
return(GetDFARatio(dfa1.Determinize(solver).Minimize(solver), dfadiff, al, solver, solutionDensity > 0.5));
}
public static bool canCollapseStates(Automaton <BDD> nfa, int state1, int state2, CharSetSolver solver, Pair <IEnumerable <string>, IEnumerable <string> > tests, HashSet <char> al)
{
var density = DFADensity.GetDFADensity(nfa, al, solver);
// collapses state2 to state1
List <Move <BDD> > newMoves = new List <Move <BDD> >();
foreach (var move in nfa.GetMoves())
{
var newSource = move.SourceState;
var newTarget = move.TargetState;
if (newSource == state2)
{
newSource = state1;
}
if (newTarget == state2)
{
newTarget = state1;
}
newMoves.Add(new Move <BDD>(newSource, newTarget, move.Label));
}
// replace state2 with state1 if initial state
// no need to remove state2 from final state list, as it is unreachable
int newInitialState = nfa.InitialState;
if (nfa.InitialState == state2)
{
newInitialState = state1;
}
//makes new Nfa and returns collapse state edit if are equiv
var newNfa = Automaton <BDD> .Create(newInitialState, nfa.GetFinalStates(), newMoves);
if (DFAUtilities.ApproximateMNEquivalent(tests, density, newNfa, al, solver))
{
return(nfa.IsEquivalentWith(newNfa, solver));
}
return(false);
}
/// <summary>
/// create new instance of NFAEdit distance and assigns a number to each character
/// </summary>
/// <param name="nfa1"></param>
/// <param name="nfa2"></param>
/// <param name="al"></param>
/// <param name="solver"></param>
/// <param name="timeout"></param>
public NFAEditDistanceProvider(Automaton <BDD> nfa1,
HashSet <char> al, CharSetSolver solver, long timeout)
{
this.nfa1 = nfa1;
this.al = al;
this.solver = solver;
this.timeout = timeout;
this.alphabetMap = new Dictionary <char, int>();
int index = 0;
foreach (var c in al)
{
this.alphabetMap[c] = index;
index++;
}
this.sw = new Stopwatch();
this.tests = NFAUtilities.MyHillTestGeneration(al, nfa1.Determinize(solver), solver);
var dfa1 = nfa1.RemoveEpsilons(solver.MkOr).Determinize(solver).Minimize(solver);
this.nfa1density = DFADensity.GetDFADensity(dfa1, al, solver);
}
/// <summary>
/// Finds min edit distance script between DFAs if operation
/// takes less than timeout ms
/// </summary>
/// <param name="dfa1"></param>
/// <param name="dfa2"></param>
/// <param name="al"></param>
/// <param name="solver"></param>
/// <param name="timeout"></param>
/// <param name="sb"></param>
/// <returns></returns>
public static DFAEditScript GetDFAOptimalEdit( // copy
Automaton <BDD> dfa1, Automaton <BDD> dfa2,
HashSet <char> al, CharSetSolver solver, long timeout,
StringBuilder sb)
{
//Contract.Assert(dfa1.IsDeterministic);
//Contract.Assert(dfa2.IsDeterministic);
DFAEditScript editScript = new DFAEditScript();
#region Add states to dfa2 to make it at least as dfa1
BDD fullAlphabetCondition = BDDOf(al, solver);
//Normalize the DFA giving only names from 0 to |States|-1
var normDfaPair = DFAUtilities.normalizeDFA(dfa2);
var dfa2augmented = normDfaPair.First;
//solver.SaveAsDot(dfa2augmented, "aaaa");
var stateNamesMapping = normDfaPair.Second;
//Add states to make dfa2 have the |dfa2.States|>= |dfa1.States|
var newMoves = new List <Move <BDD> >(dfa2augmented.GetMoves());
for (int i = 1; i <= dfa1.StateCount - dfa2augmented.StateCount; i++)
{
int newStateName = dfa2augmented.MaxState + i;
//Pick the next available name to be added
stateNamesMapping[newStateName] = dfa2.MaxState + i;
//save the operation in the script
editScript.script.Insert(0, new DFAAddState(dfa2.MaxState + i));
newMoves.Add(new Move <BDD>(newStateName, newStateName, fullAlphabetCondition));
newStateName++;
}
//Create the new DFA with the added states
dfa2augmented = Automaton <BDD> .Create(dfa2augmented.InitialState, dfa2augmented.GetFinalStates().ToList(), newMoves);
#endregion
int maxScore = (dfa1.StateCount + dfa2augmented.StateCount) * (al.Count + 1);
int oldScirptSize = editScript.script.Count;
//Start with the internal script equals to null, at the end bestScript.Script will contain the best script
DFAEditScript bestScript = new DFAEditScript();
bestScript.script = null;
Stopwatch sw = new Stopwatch();
sw.Start();
// Iteratively check if there exists an edit of a given depth
for (int depth = 1; true; depth++)
{
var editList = new List <DFAEdit>();
if (GetDFAEditScriptTimeout(
dfa1, dfa2augmented, al, solver,
new List <long>(), editScript.script,
depth, timeout, sw, DFAUtilities.MyHillTestGeneration(al, dfa1, solver),
DFADensity.GetDFADensity(dfa1, al, solver),
editScript.GetCost(), bestScript, stateNamesMapping))
{
// if hits timeout break and return null
break;
}
if (bestScript.script != null)
{
bestScript.script.Reverse();
sw.Stop();
return(bestScript);
}
}
sw.Stop();
return(null);
}
