// TODO: Uses non-reachable states (inefficient)
TriangularPair <int>[] GetEquivalentPairs()
{
// table filling algorithm:
var undistinguishablePairs = new HashSet <TriangularPair <int> >(); // not marked!!!
// basis
foreach (int p in _delta.Keys)
{
foreach (int q in _delta.Keys)
{
if (q <= p)
{
continue; // triangular
}
if (!IsBasisDistinguishable(p, q))
{
undistinguishablePairs.Add(new TriangularPair <int>(p, q));
}
}
}
// induction
while (true)
{
// marked pairs in this induction step
var marked = new List <TriangularPair <int> >();
foreach (TAlphabet successorLabel in GetLabels())
{
foreach (var pair in undistinguishablePairs)
{
// Make function with input loop
// IsInductionDistinguishable
//int p = Trans[pair.Fst][successorLabel];
//int q = Trans[pair.Snd][successorLabel];
if (_delta[pair.Fst].TryGetValue(successorLabel, out var p) &&
_delta[pair.Snd].TryGetValue(successorLabel, out var q))
{
TriangularPair <int> successorPair = new TriangularPair <int>(p, q);
// For all pairs still undecided if for any successor label/input/suffix
// the pair goes into a pair (p, q) where the states are distinguishable
// for any suffix (that is already marked) we have to mark the pair.
// NOTE: BAD that we have to test p not equal to q (use marked table instead)
if (p != q && !undistinguishablePairs.Contains(successorPair)) // successor pair is marked
{
marked.Add(pair);
}
}
}
//Debug.WriteLine($"Step {step}, Input = {successorLabel}, Count = {markedPerInput.Count}: " +
// markedPerInput.Select(p =>
// $"({_renamer.ToDfaStateString(p.Fst)}, {_renamer.ToDfaStateString(p.Snd)})")
// .ToSetNotation());
}
foreach (var pair in marked)
{
undistinguishablePairs.Remove(pair); // no-op for duplicates
}
if (marked.Count == 0)
{
break; // no more distinguishable pairs have been removed
}
}
// the following pairs are equivalent
return(undistinguishablePairs.ToArray());
}
public bool Equals(TriangularPair <T> other)
{
return(EqualityComparer <T> .Default.Equals(Fst, other.Fst) &&
EqualityComparer <T> .Default.Equals(Snd, other.Snd));
}