/// <summary>
/// Minimizes (and determinizes if not already deterministic) the given automaton.
/// </summary>
/// <param name="a">The automaton.</param>
public static void Minimize(Automaton a)
{
if (!a.IsSingleton)
{
switch (Automaton.Minimization)
{
case Automaton.MinimizeHuffman:
MinimizationOperations.MinimizeHuffman(a);
break;
case Automaton.MinimizeBrzozowski:
MinimizationOperations.MinimizeBrzozowski(a);
break;
default:
MinimizationOperations.MinimizeHopcroft(a);
break;
}
}
a.RecomputeHashCode();
}
/// <summary>
/// The minimize.
/// </summary>
public void Minimize()
{
MinimizationOperations.Minimize(this);
}
/// <summary>
/// Minimizes the given automaton using Huffman's algorithm.
/// </summary>
/// <param name="a">The automaton.</param>
internal static void MinimizeHuffman(Automaton a)
{
a.Determinize();
a.Totalize();
HashSet <State> ss = a.GetStates();
var transitions = new Transition[ss.Count][];
State[] states = ss.ToArray();
var mark = new List <List <bool> >();
var triggers = new List <List <HashSet <IntPair> > >();
foreach (State t in states)
{
var v = new List <HashSet <IntPair> >();
Initialize(ref v, states.Length);
triggers.Add(v);
}
// Initialize marks based on acceptance status and find transition arrays.
for (int n1 = 0; n1 < states.Length; n1++)
{
states[n1].Number = n1;
transitions[n1] = states[n1].GetSortedTransitions(false).ToArray();
for (int n2 = n1 + 1; n2 < states.Length; n2++)
{
if (states[n1].Accept != states[n2].Accept)
{
mark[n1][n2] = true;
}
}
}
// For all pairs, see if states agree.
for (int n1 = 0; n1 < states.Length; n1++)
{
for (int n2 = n1 + 1; n2 < states.Length; n2++)
{
if (!mark[n1][n2])
{
if (MinimizationOperations.StatesAgree(transitions, mark, n1, n2))
{
MinimizationOperations.AddTriggers(transitions, triggers, n1, n2);
}
else
{
MinimizationOperations.MarkPair(mark, triggers, n1, n2);
}
}
}
}
// Assign equivalence class numbers to states.
int numclasses = 0;
foreach (State t in states)
{
t.Number = -1;
}
for (int n1 = 0; n1 < states.Length; n1++)
{
if (states[n1].Number == -1)
{
states[n1].Number = numclasses;
for (int n2 = n1 + 1; n2 < states.Length; n2++)
{
if (!mark[n1][n2])
{
states[n2].Number = numclasses;
}
}
numclasses++;
}
}
// Make a new state for each equivalence class.
var newstates = new State[numclasses];
for (int n = 0; n < numclasses; n++)
{
newstates[n] = new State();
}
// Select a class representative for each class and find the new initial state.
for (int n = 0; n < states.Length; n++)
{
newstates[states[n].Number].Number = n;
if (states[n] == a.Initial)
{
a.Initial = newstates[states[n].Number];
}
}
// Build transitions and set acceptance.
for (int n = 0; n < numclasses; n++)
{
State s = newstates[n];
s.Accept = states[s.Number].Accept;
foreach (Transition t in states[s.Number].Transitions)
{
s.Transitions.Add(new Transition(t.Min, t.Max, newstates[t.To.Number]));
}
}
a.RemoveDeadTransitions();
}
/// <summary>
/// The minimize.
/// </summary>
internal void Minimize()
{
MinimizationOperations.Minimize(this);
}
