// Returns first collapse edit found that shrinks nfa2
// Returns null if none found
// Returns null if nfa2 is not equivalent with nfa1
public NFAEdit NFACollapseSearch(Automaton <BDD> nfa2)
{
//Makes sure the two nfas are equivalent
if (!nfa1.IsEquivalentWith(nfa2, solver))
{
return(null);
}
nfa2 = NFAUtilities.normalizeMoves(nfa2, solver);
// checks if any state can be removed
foreach (var state in nfa2.States)
{
if (state != nfa2.InitialState)
{
if (NFAUtilities.canRemoveState(nfa2, state, solver, tests, al))
{
return(new NFARemoveState(state));
}
}
}
// checks if any move can be removed
foreach (var state1 in nfa2.States)
{
foreach (var state2 in nfa2.States)
{
if (state1 < state2)
{
if (NFAUtilities.canCollapseStates(nfa2, state1, state2, solver, tests, al))
{
return(new NFACollapseStates(state1, state2));
}
}
}
}
// checks if any move can be removed
foreach (var state1 in nfa2.States)
{
foreach (var state2 in nfa2.States)
{
if (NFAUtilities.canRemoveEdge(nfa2, state1, state2, solver, tests, al))
{
return(new NFARemoveEdge(state1, state2));
}
}
}
//returns null if search fails
return(null);
}
/// <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);
}
// looks for an edit at depth "depth"
// returns false and null in bestScript if no edit is found at depth "depth"
// returns false and not null in bestScript if found
// returns true if timeout
internal bool GetNFAEditScriptTimeout(
int depth, long lastEditHash,
Automaton <BDD> currentNfa2,
List <NFAEdit> editList, int scriptCost,
NFAEditScript bestScript)
{
// if timeout return true
if (sw.ElapsedMilliseconds > timeout)
{
return(true);
}
//Stop if no more moves left
if (depth == 0)
{
if (DFAUtilities.ApproximateMNEquivalent(tests, nfa1density, currentNfa2, al, solver) && currentNfa2.IsEquivalentWith(nfa1, solver))
{
//check if totalCost < finalScript cost and replace if needed
if (bestScript.script == null || scriptCost < bestScript.GetCost())
{
bestScript.script = ObjectCopier.Clone <List <NFAEdit> >(editList);
}
}
return(false);
}
NFAEdit edit = null;
long thisEditHash = 0;
#region Flip one state from fin to non fin
foreach (var state in currentNfa2.States)
{
thisEditHash = state;
if (CanAdd(thisEditHash, lastEditHash))
{
//flip its final non final status
var newFinalStates = new HashSet <int>(currentNfa2.GetFinalStates());
Automaton <BDD> nfa2new = null;
if (currentNfa2.GetFinalStates().Contains(state))
{
edit = new NFAEditState(state, false);
editList.Insert(0, edit);
newFinalStates.Remove(state);
nfa2new = Automaton <BDD> .Create(currentNfa2.InitialState, newFinalStates, currentNfa2.GetMoves());
}
else
{
edit = new NFAEditState(state, true);
editList.Insert(0, edit);
newFinalStates.Add(state);
nfa2new = Automaton <BDD> .Create(currentNfa2.InitialState, newFinalStates, currentNfa2.GetMoves());
}
if (GetNFAEditScriptTimeout(depth - 1, thisEditHash, nfa2new, editList, scriptCost + edit.GetCost(), bestScript))
{
return(true);
}
editList.RemoveAt(0);
}
}
#endregion
#region Change transition from source state
currentNfa2 = NFAUtilities.normalizeMoves(currentNfa2, solver);
foreach (var sourceState in currentNfa2.States)
{
HashSet <int> unreachedStates = new HashSet <int>(currentNfa2.States);
foreach (var moveFromSource in currentNfa2.GetMovesFrom(sourceState))
{
// take all chars in alphabet
foreach (var c in al)
{
long moveHash = currentNfa2.StateCount + IntegerUtil.TripleToInt(sourceState, moveFromSource.TargetState, alphabetMap[c]);
thisEditHash = currentNfa2.StateCount + moveHash;
if (CanAdd(thisEditHash, lastEditHash))
{
BDD cCond = solver.False;
BDD newCond = solver.False;
//skip epsilon moves
if (moveFromSource.Label != null)
{
// if c in move, remove it and recursion
if (solver.Contains(moveFromSource.Label, c))
{
cCond = solver.MkNot(solver.MkCharConstraint(false, c));
newCond = solver.MkAnd(moveFromSource.Label, cCond);
}
else // if c not in move, add it and recursion
{
cCond = solver.MkCharConstraint(false, c);
newCond = solver.MkOr(moveFromSource.Label, cCond);
}
var newMoves = new List <Move <BDD> >(currentNfa2.GetMoves());
newMoves.Remove(moveFromSource);
newMoves.Add(new Move <BDD>(sourceState, moveFromSource.TargetState, newCond));
var nfa2new = Automaton <BDD> .Create(currentNfa2.InitialState, currentNfa2.GetFinalStates(), newMoves);
edit = new NFAEditMove(sourceState, moveFromSource.TargetState, c);
editList.Insert(0, edit);
if (GetNFAEditScriptTimeout(depth - 1, thisEditHash, nfa2new, editList, scriptCost + edit.GetCost(), bestScript))
{
return(true);
}
editList.RemoveAt(0);
}
}
}
unreachedStates.Remove(moveFromSource.TargetState);
}
foreach (var targetState in unreachedStates)
{
//try adding a symbol not in transition
foreach (var c in al)
{
long moveHash = IntegerUtil.TripleToInt(sourceState, targetState, alphabetMap[c]);
thisEditHash = currentNfa2.StateCount + moveHash;
var moveCond = solver.MkCharConstraint(false, c);
var newMoves = new List <Move <BDD> >(currentNfa2.GetMoves());
newMoves.Add(new Move <BDD>(sourceState, targetState, moveCond));
var nfa2new = Automaton <BDD> .Create(currentNfa2.InitialState, currentNfa2.GetFinalStates(), newMoves);
edit = new NFAEditMove(sourceState, targetState, c);
editList.Insert(0, edit);
//TODO put correct hash
if (GetNFAEditScriptTimeout(depth - 1, thisEditHash, nfa2new, editList, scriptCost + edit.GetCost(), bestScript))
{
return(true);
}
editList.RemoveAt(0);
}
}
}
#endregion
return(false);
}