/// <summary>
/// Counts the number of nodes (both terminals and nonterminals) in the BDD.
/// </summary>
public int CountNodes()
{
if (IsLeaf)
{
return(1);
}
HashSet <BDD> visited = new HashSet <BDD>();
SimpleStack <BDD> stack = new SimpleStack <BDD>();
stack.Push(this);
visited.Add(this);
while (stack.IsNonempty)
{
BDD a = stack.Pop();
if (!a.IsLeaf)
{
if (visited.Add(a.One))
{
stack.Push(a.One);
}
if (visited.Add(a.Zero))
{
stack.Push(a.Zero);
}
}
}
return(visited.Count);
}
/// <summary>
/// Computes (number of nonterminals, number of terminals) in the underlying directed acyclic graph.
/// </summary>
public Tuple <int, int> GetSize()
{
int nrNodes = 0;
int nrLeaves = 0;
HashSet <BDG <T, S> > done = new HashSet <BDG <T, S> >();
SimpleStack <BDG <T, S> > stack = new SimpleStack <BDG <T, S> >();
stack.Push(this);
done.Add(this);
while (stack.IsNonempty)
{
var bdg = stack.Pop();
if (bdg.IsLeaf)
{
nrLeaves += 1;
}
else
{
if (done.Add(bdg.TrueCase))
{
stack.Push(bdg.TrueCase);
}
if (done.Add(bdg.FalseCase))
{
stack.Push(bdg.FalseCase);
}
nrNodes += 1;
}
}
return(new Tuple <int, int>(nrNodes, nrLeaves));
}
/// <summary>
/// Based on MinimizeMoore method/technique.
/// </summary>
void Initialize()
{
var fa = aut;
var currLayer = new SimpleStack <Tuple <int, int> >();
var nextLayer = new SimpleStack <Tuple <int, int> >();
//any pair of states (p,q) where one state is final and the other is not are distinguished by
//the empty list represented by null, this set of distinguishing sequences is trivially suffix-closed
foreach (var p in fa.GetStates())
{
if (!fa.IsFinalState(p))
{
foreach (var q in fa.GetFinalStates())
{
var pair = MkPair(p, q);
if (!distinguisher.ContainsKey(pair))
{
//the empty sequence distinguishes the states
distinguisherConcrete[pair] = "";
//List<Pair> pairs;
//if (!distinguishingStringsMap.TryGetValue("", out pairs))
//{
// pairs = new List<Tuple<int, int>>();
// distinguishingStringsMap[""] = pairs;
// distinguishingStringsSeq.Add("");
//}
//pairs.Add(pair);
distinguisher[pair] = null;
nextLayer.Push(pair);
}
}
}
}
//if a target pair of states is distinguished by some sequence
//then any pair entering those states is also distinguished by extending that sequence
//work breadth-first to maintain shortest witnesses
while (nextLayer.IsNonempty)
{
var tmp = currLayer;
currLayer = nextLayer;
nextLayer = new SimpleStack <Tuple <int, int> >();
while (currLayer.IsNonempty)
{
var targetpair = currLayer.Pop();
foreach (var m1 in fa.GetMovesTo(targetpair.Item1))
{
foreach (var m2 in fa.GetMovesTo(targetpair.Item2))
{
if (m1.SourceState != m2.SourceState)
{
var psi = solver.MkAnd(m1.Label, m2.Label);
if (solver.IsSatisfiable(psi))
{
var sourcepair = MkPair(m1.SourceState, m2.SourceState);
if (!distinguisher.ContainsKey(sourcepair))
{
//add a new distinguishing sequence for the source pair
//it extends a sequence of the target pair
//thus the sequences remain suffix-closed
if (concretize != null)
{
#region when concretization function is given precompute concrete distinguishers
char c;
if (!selectedCharacterMap.TryGetValue(psi, out c))
{
c = concretize(psi);
selectedCharacterMap[psi] = c;
}
var s = c + distinguisherConcrete[targetpair];
distinguisherConcrete[sourcepair] = s;
//List<Pair> pairs;
//if (!distinguishingStringsMap.TryGetValue(s, out pairs))
//{
// pairs = new List<Tuple<int, int>>();
// distinguishingStringsMap[s] = pairs;
// distinguishingStringsSeq.Add(s);
//}
//pairs.Add(sourcepair);
#endregion
}
var list = new ConsList <T>(psi, distinguisher[targetpair]);
distinguisher[sourcepair] = list;
nextLayer.Push(sourcepair);
}
}
}
}
}
}
}
}
public STb <FUNC, TERM, SORT> Compose()
{
var stack = new SimpleStack <Tuple <int, int> >();
int stateId = 1;
var stateIdMap = new Dictionary <Tuple <int, int>, int>();
var revStateIdMap = new Dictionary <int, Tuple <int, int> >();
var q0A_x_q0B = new Tuple <int, int>(A.InitialState, B.InitialState);
stack.Push(q0A_x_q0B);
stateIdMap[q0A_x_q0B] = 0;
revStateIdMap[0] = q0A_x_q0B;
Func <int, int, int> ComposeStates = (x, y) =>
{
var xy = new Tuple <int, int>(x, y);
int q;
if (stateIdMap.TryGetValue(xy, out q))
{
return(q);
}
else
{
q = stateId;
stateId += 1;
stateIdMap[xy] = q;
revStateIdMap[q] = xy;
stack.Push(xy);
return(q);
}
};
var A2B = new STb <FUNC, TERM, SORT>(solver, A.Name + "2" + B.Name, A.InputSort, B.OutputSort, regSort, JoinRegs(A.InitialRegister, B.InitialRegister), 0);
//create normal composed rules
while (stack.IsNonempty)
{
var qA_x_qB = stack.Pop();
var qA = qA_x_qB.Item1;
var qB = qA_x_qB.Item2;
var ruleA = A.GetRuleFrom(qA);
if (ruleA.IsNotUndef)
{
var qAB_rule = Comp(solver.True, ruleA, qB, ComposeStates, false);
A2B.AssignRule(stateIdMap[qA_x_qB], qAB_rule);
}
else
{
A2B.AssignRule(stateIdMap[qA_x_qB], UndefRule <TERM> .Default);
}
}
foreach (var qAB in A2B.States)
{
var qA_x_qB = revStateIdMap[qAB];
var qA = qA_x_qB.Item1;
var qB = qA_x_qB.Item2;
var ruleA = A.GetFinalRuleFrom(qA);
if (ruleA.IsNotUndef)
{
var qAB_Frule = Comp(solver.True, ruleA, qB, (p, q) => qAB, true);
A2B.AssignFinalRule(qAB, qAB_Frule);
}
}
A2B.EliminateDeadends();
//Func<Rule<TERM>, Rule<TERM>> ReplaceWithEpsilon = (r) =>
// {
// };
//var aut = A2B.ToST(true).automaton.RelpaceAllGuards(ReplaceWithEpsilon);
return(A2B);
}
//public List<Move<Rule<T>>> CoveredMoves
//{
// get { return covered_moves; }
//}
public void Explore()
{
var seen_states = new HashSet <int>();
seen_states.Add(stb.InitialState);
var stack = new SimpleStack <Tuple <int, T> >();
var stack_next = new SimpleStack <Tuple <int, T> >();
var seen_next = new HashSet <Tuple <int, T> >();
stack_next.Push(new Tuple <int, T>(stb.InitialState, stb.InitialRegister));
while (stack_next.IsNonempty)
{
foreach (var p_r in seen_next)
{
seen_states.Add(p_r.Item1);
}
var tmp = stack;
stack = stack_next;
stack_next = tmp;
seen_next.Clear();
while (stack.IsNonempty)
{
var q_r = stack.Pop();
var q = q_r.Item1;
var r_in = q_r.Item2;
foreach (var dir_move in moves[q])
{
var move = dir_move.Item3;
var guard1 = Z.ApplySubstitution(move.Label.Guard, stb.RegVar, r_in);
var witness = Z.MainSolver.FindOneMember(Z.MkAnd(guard1, Z.MkEq(stb.InputVar, stb.InputVar)));
if (witness != null)
{
var r_out = Z.Simplify(Z.ApplySubstitution(move.Label.Update, stb.InputVar, witness.Value, stb.RegVar, r_in));
var p_r = new Tuple <int, T>(move.TargetState, r_out);
if (!exploredSteps.ContainsKey(q))
{
exploredSteps[q] = new Dictionary <Tuple <T, T>, Tuple <int, T> >();
}
exploredSteps[q][new Tuple <T, T>(witness.Value, r_in)] = p_r;
if (!seen_states.Contains(move.TargetState))
{
if (seen_next.Add(p_r))
{
stack_next.Push(p_r);
}
}
}
else //the move is inaccessible from this state (and register value) since guard1 is unsatisfiable
{
uncovered_moves.Add(dir_move);
}
}
foreach (var dir_fmove in final_moves[q])
{
var fmove = dir_fmove.Item3;
var guard1 = Z.Simplify(Z.ApplySubstitution(fmove.Label.Guard, stb.RegVar, r_in));
if (guard1.Equals(stb.Solver.False))
{
uncovered_final_moves.Add(dir_fmove);
}
}
}
}
}
/// <summary>
/// Generate method code for a given BDD with given methid as method name
/// </summary>
private static void GenerateCodeForBDD(StringBuilder code, BDD pred, string methid)
{
Dictionary <BDD, int> idMap = new Dictionary <BDD, int>();
int nextLabelId = 0;
Func <BDD, int> getId = bdd =>
{
int bddid;
if (!idMap.TryGetValue(bdd, out bddid))
{
bddid = nextLabelId++;
idMap[bdd] = bddid;
}
return(bddid);
};
HashSet <BDD> done = new HashSet <BDD>();
SimpleStack <BDD> todo = new SimpleStack <BDD>();
todo.Push(pred);
done.Add(pred);
StringBuilder leaves = new StringBuilder();
while (todo.IsNonempty)
{
var bdd = todo.Pop();
if (bdd.IsLeaf)
{
leaves.Append(String.Format("\r\n P{0}_{1}: return {2};", methid, getId(bdd), bdd.IsEmpty ? "false" : "true"));
}
else
{
BDD exit = !bdd.Zero.IsLeaf && (bdd.Zero.Zero == bdd.One || bdd.Zero.One == bdd.One) ? bdd.One : bdd.Zero;
BDD continuation = bdd;
int zeros = 0;
int ones = 0;
while (true)
{
if (exit == continuation.Zero)
{
zeros |= 1 << continuation.Ordinal;
continuation = continuation.One;
}
else if (exit == continuation.One)
{
ones |= 1 << continuation.Ordinal;
continuation = continuation.Zero;
}
else
{
break;
}
}
var anyZero = string.Format("(c & 0x{0:X}) != 0x{0:X}", zeros);
var anyOne = string.Format("(c & 0x{0:X}) != 0", ones);
var exitCondition = zeros == 0 ? anyOne : ones == 0 ? anyZero : string.Format("({0}) || ({1})", anyOne, anyZero);
code.Append(string.Format(@"
"));
if (bdd != pred)
{
code.Append(string.Format("P{0}_{1}: ", methid, getId(bdd)));
}
code.Append(string.Format("if ({2}) goto P{0}_{3}; else goto P{0}_{4};", methid, getId(bdd), exitCondition, getId(exit), getId(continuation)));
if (done.Add(exit))
{
todo.Push(exit);
}
if (done.Add(continuation))
{
todo.Push(continuation);
}
}
}
code.Append(leaves.ToString());
}
/// <summary>
/// Explores the PDA and converts it into an automaton,
/// only stacks up to bounded depth are considered.
/// </summary>
/// <param name="stackDepth">upper bound on reached stack depth, nonpositive value means unbounded and may cause nontermination</param>
public Automaton <T> Explore(int stackDepth = 0)
{
var moves = new List <Move <T> >();
var stateMap = new Dictionary <Tuple <int, Sequence <S> >, int>();
var configMap = new Dictionary <int, Tuple <int, Sequence <S> > >();
var finalStates = new HashSet <int>();
int q0 = 0;
var config0 = new Tuple <int, Sequence <S> >(this.automaton.InitialState, new Sequence <S>(this.initialStackSymbol));
int nextStateId = 1;
stateMap[config0] = q0;
configMap[q0] = config0;
if (automaton.IsFinalState(this.automaton.InitialState))
{
finalStates.Add(q0);
}
var movemap = new Dictionary <Tuple <int, int>, T>();
Action <int, int, T> AddMove = (source, target, pred) =>
{
var key = new Tuple <int, int>(source, target);
T psi;
if (movemap.TryGetValue(key, out psi))
{
movemap[key] = this.terminalAlgebra.MkOr(psi, pred);
}
else
{
movemap[key] = pred;
}
};
var frontier = new SimpleStack <int>();
frontier.Push(q0);
while (frontier.IsNonempty)
{
int q = frontier.Pop();
var config = configMap[q];
foreach (var move in automaton.GetMovesFrom(config.Item1))
{
if (stackDepth < 1 || (config.Item2.Length - 1 + move.Label.PushSymbols.Length) <= stackDepth)
{
var pop = move.Label.PopSymbol;
var push = move.Label.PushSymbols;
if (config.Item2.First.Equals(pop))
{
var targetConfig = new Tuple <int, Sequence <S> >(move.TargetState, push.Append(config.Item2.Rest()));
int target;
if (!stateMap.TryGetValue(targetConfig, out target))
{
target = nextStateId++;
stateMap[targetConfig] = target;
configMap[target] = targetConfig;
frontier.Push(target);
if (automaton.IsFinalState(move.TargetState))
{
finalStates.Add(target);
}
}
Move <T> newmove;
if (move.Label.InputIsEpsilon)
{
newmove = Move <T> .Epsilon(q, target);
moves.Add(newmove);
}
else
{
//accumulate predicates for transitions
AddMove(q, target, move.Label.Input);
}
}
}
}
}
foreach (var entry in movemap)
{
moves.Add(Move <T> .Create(entry.Key.Item1, entry.Key.Item2, entry.Value));
}
var res = Automaton <T> .Create(this.terminalAlgebra, q0, finalStates, moves, false, true);
return(res);
}
PushdownAutomaton <S, T> Intersect1(IMinimalAutomaton <T> nfa)
{
//depth first product construction, PDA may have epsilon moves
var stateIdMap = new Dictionary <Pair, int>();
int nextStateId = 1;
var stack = new SimpleStack <Pair>();
var moves = new List <Move <PushdownLabel <S, T> > >();
var states = new List <int>();
var finalstates = new List <int>();
#region GetState: push the pair to stack if the state id was new and update final states as needed
Func <Pair, int> GetState = (pair) =>
{
int id;
if (!stateIdMap.TryGetValue(pair, out id))
{
id = nextStateId;
nextStateId += 1;
stateIdMap[pair] = id;
stack.Push(pair);
states.Add(id);
if (this.automaton.IsFinalState(pair.Item1) && nfa.IsFinalState(pair.Item2))
{
finalstates.Add(id);
}
}
return(id);
};
#endregion
var initPair = new Pair(this.automaton.InitialState, nfa.InitialState);
int initState = GetState(initPair);
#region compute the product transitions with depth-first search
while (stack.IsNonempty)
{
var sourcePair = stack.Pop();
var source = stateIdMap[sourcePair];
var pda_state = sourcePair.Item1;
var aut_state = sourcePair.Item2;
foreach (var pda_move in this.automaton.GetMovesFrom(pda_state))
{
if (pda_move.IsEpsilon || pda_move.Label.InputIsEpsilon)
{
var targetPair = new Pair(pda_move.TargetState, aut_state);
int target = GetState(targetPair);
moves.Add(Move <PushdownLabel <S, T> > .Create(source, target, pda_move.Label));
}
else
{
//assuming here that the automaton does not have epsilons
foreach (var aut_move in nfa.GetMovesFrom(aut_state))
{
if (aut_move.IsEpsilon)
{
throw new AutomataException(AutomataExceptionKind.AutomatonIsNotEpsilonfree);
}
var cond = nfa.Algebra.MkAnd(aut_move.Label, pda_move.Label.Input);
//if the joint condition is not satisfiable then the
//joint move does effectively not exist
if (nfa.Algebra.IsSatisfiable(cond))
{
var targetPair = new Pair(pda_move.TargetState, aut_move.TargetState);
int target = GetState(targetPair);
var label = new PushdownLabel <S, T>(cond, pda_move.Label.PushAndPop);
var jointmove = Move <PushdownLabel <S, T> > .Create(source, target, label);
moves.Add(jointmove);
}
}
}
}
}
#endregion
//note: automaton creation eliminates unreachable states and deadend states from the product
var productAutom = Automaton <PushdownLabel <S, T> > .Create(null, initState, finalstates, moves, true, true);
var product = new PushdownAutomaton <S, T>(nfa.Algebra, productAutom, this.stackSymbols, this.initialStackSymbol);
return(product);
}
/// <summary>
/// Algorithm 'saturate' in Figure 1 from Finkel-Willems-Wolper paper
/// 'A Direct Symbolic Approach to Model Checking PushDown Systems'
/// </summary>
/// <returns></returns>
internal HashSet <Trans> Saturate()
{
var hash = new HashSet <Trans>();
var stack = new SimpleStack <Trans>();
foreach (var q in this.Q)
{
stack.Push(MkTrans(q, q));
}
var direct = new Dictionary <Trans, SimpleStack <Trans> >();
var trans = new Dictionary <Trans, SimpleStack <Tuple <Trans, Trans> > >();
Func <Trans, SimpleStack <Trans> > Direct = (t) =>
{
SimpleStack <Trans> t_stack;
if (!direct.TryGetValue(t, out t_stack))
{
t_stack = new SimpleStack <Trans>();
direct[t] = t_stack;
}
return(t_stack);
};
Func <Trans, SimpleStack <Tuple <Trans, Trans> > > Transfer = (t) =>
{
SimpleStack <Tuple <Trans, Trans> > t_trans;
if (!trans.TryGetValue(t, out t_trans))
{
t_trans = new SimpleStack <Tuple <Trans, Trans> >();
trans[t] = t_trans;
}
return(t_trans);
};
foreach (var a in pda.stackSymbols)
{
foreach (var push in pushMap[a])
{
foreach (var pop in popMap[a])
{
//push_pop goes from target of push to source of pop
var push_pop = MkTrans(push.Item2, pop.SourceState);
//edge goes from source of push to target of pop
var edge = MkTrans(push.Item1, pop.TargetState);
Direct(push_pop).Push(edge);
}
}
}
foreach (var q in Q)
{
foreach (var p in Q)
{
var qp = MkTrans(q, p);
var qp_trans = Transfer(qp);
foreach (var t in Q)
{
var pt = MkTrans(p, t);
var qt = MkTrans(q, t);
var pt_qt = new Tuple <Trans, Trans>(pt, qt);
var tq = MkTrans(t, q);
var tp = MkTrans(t, p);
var tq_tp = new Tuple <Trans, Trans>(tq, tp);
qp_trans.Push(pt_qt);
qp_trans.Push(tq_tp);
}
}
}
while (stack.IsNonempty)
{
var alpha = stack.Pop();
hash.Add(alpha);
stack.PushAll(direct[alpha]);
foreach (var pair in Transfer(alpha))
{
if (hash.Contains(pair.Item1))
{
stack.Push(pair.Item2);
}
else
{
Direct(pair.Item1).Push(pair.Item2);
}
}
}
return(hash);
}
