/// <summary>
/// Get the maximim walking distance from any index of the given <see cref="ITransition"/> to
/// its corresonding strongly connected group.
/// </summary>
/// <returns>The maximum walking distance from any index to a strongly connected group.</returns>
/// <param name="transition">The given <see cref="ITransition"/> for which this distance is calculated.</param>
/// <seealso cref="M:GetStronlyConnectedPeriod"/>
public static int GetStronlyConnectedPeriod(this ITransition transition)
{
int n = transition.Length;
CompactBitVector glb = CompactBitVector.All(n);
CompactBitVector cur = CompactBitVector.All(n);
int low = 0x00, idx, rem, siz, period = 0x01;
Stack <int> stack = new Stack <int> ();
do
{
idx = low;
do
{
cur.Remove(idx);
stack.Push(idx);
idx = transition.GetTransitionOfIndex(idx);
} while(cur.Contains(idx) && glb.Contains(idx));
if (glb.Contains(idx)) //we've found a new group
{
siz = 0x00;
do
{
rem = stack.Pop();
siz++;
} while(rem != idx);
period = MathUtils.LeastCommonMultiple(period, siz);
}
stack.Clear();
glb.AndLocal(cur);
low = glb.GetLowest(low + 0x01);
} while(low > 0x00);
return(period);
}
/// <summary>
/// Calculate for each index of the transition the distance towards its strongly connected group and the
/// tour size of that group.
/// </summary>
/// <returns>A <see cref="T:Tuple`2"/> containing two arrays. The first array contains the distance
/// to a strongly connected group for the index of the transition. The second index contains
/// the tour size the strongly connected group of the index of the transition.</returns>
/// <param name="transition">The transition to calculate these values for.</param>
/// <param name="distances">An array containing the distances to the corresponding strongly connected groups.</param>
/// <param name="tourLengths">An array containing the tour lengths of the corresponding strongly connected groups.</param>
/// <param name="initialTours">An array containing the first index of the strongly connected group.</param>
public static void GetStronglyConnectedGroupsDistanceTour(this ITransition transition, out int[] distances, out int[] tourLengths, out int[] initialTours)
{
int n = transition.Length;
CompactBitVector glb = CompactBitVector.All(n);
CompactBitVector cur = CompactBitVector.All(n);
distances = new int[n];
tourLengths = new int[n];
initialTours = new int[n];
int low = 0x00, idx, ini, rem, dist, tour;
Stack <int> stack = new Stack <int> ();
Stack <int> ttack = new Stack <int> ();
do
{
idx = low;
do
{
cur.Remove(idx);
stack.Push(idx);
idx = transition.GetTransitionOfIndex(idx);
} while(cur.Contains(idx) && glb.Contains(idx));
if (glb.Contains(idx)) //we've found a new group
{
tour = 0x00;
ini = idx;
do
{
tour++;
rem = stack.Pop();
distances [rem] = 0x00;
initialTours [rem] = rem;
ttack.Push(rem);
} while(rem != idx);
while (ttack.Count > 0x00)
{
tourLengths [ttack.Pop()] = tour;
}
dist = 0x00;
}
else
{
dist = distances [idx];
tour = tourLengths [idx];
ini = initialTours [idx];
}
while (stack.Count > 0x00)
{
rem = stack.Pop();
distances [rem] = ++dist;
tourLengths [rem] = tour;
initialTours [rem] = ini;
}
glb.AndLocal(cur);
low = glb.GetLowest(low + 0x01);
} while(low > 0x00);
}
/// <summary>
/// Get the maximim walking distance from any index of the given <see cref="ITransition"/> to
/// its corresonding strongly connected group.
/// </summary>
/// <returns>The maximum walking distance from any index to a strongly connected group.</returns>
/// <param name="transition">The given <see cref="ITransition"/> for which this distance is calculated.</param>
/// <seealso cref="M:GetStronlyConnectedPeriod"/>
public static int GetMaximumStronglyConnectedGroupsDistance(this ITransition transition)
{
int n = transition.Length;
CompactBitVector glb = CompactBitVector.All(n);
CompactBitVector cur = CompactBitVector.All(n);
int[] dists = new int[n]; //TODO replace with numbervector?
int low = 0x00, idx, rem, dist, maxdist = 0x00;
Stack <int> stack = new Stack <int> ();
do
{
idx = low;
do
{
cur.Remove(idx);
stack.Push(idx);
idx = transition.GetTransitionOfIndex(idx);
} while(cur.Contains(idx) && glb.Contains(idx));
if (glb.Contains(idx)) //we've found a new group
{
do
{
rem = stack.Pop();
dists [rem] = 0x00;
} while(rem != idx);
dist = 0x00;
}
else
{
dist = dists [idx];
}
while (stack.Count > 0x00)
{
dists [stack.Pop()] = ++dist;
}
maxdist = Math.Max(maxdist, dist);
glb.AndLocal(cur);
low = glb.GetLowest(low + 0x01);
} while(low > 0x00);
return(maxdist);
}
/// <summary>
/// Enumerate the sets of strongly connected groups: indices that form a cycle.
/// </summary>
/// <returns>A <see cref="T:IEnumerable`1"/> that contains the indices of strongly connected groups.</returns>
/// <remarks>
/// <para>The strongly connected groups are generated lazily: on demand the next group is generated.</para>
/// <para>There is no guarantee on the order of the generated groups, nor on the first element of
/// every group.</para>
/// <para>Singleton groups are generated as well: indices that have a transition to themselves.</para>
/// <para>The algorithm is a special case of Tarjans algorithm especially optimized for the transition
/// functions.</para>
/// </remarks>
public static IEnumerable <IEnumerable <int> > GetStronglyConnectedGroups(this ITransition transition)
{
int n = transition.Length;
CompactBitVector glb = CompactBitVector.All(n);
CompactBitVector cur = CompactBitVector.All(n);
int low = 0x00, idx, rem;
Queue <int> pushQueue = new Queue <int> ();
do
{
idx = low;
do
{
cur.Remove(idx);
pushQueue.Enqueue(idx);
idx = transition.GetTransitionOfIndex(idx);
} while(cur.Contains(idx) && glb.Contains(idx));
if (glb.Contains(idx)) //we've found a new group
{
pushQueue.Enqueue(idx);
do
{
rem = pushQueue.Dequeue();
} while(rem != idx);
yield return(pushQueue);
pushQueue = new Queue <int> ();
}
else
{
pushQueue.Clear();
}
glb.AndLocal(cur);
low = glb.GetLowest(low + 0x01);
} while(low > 0x00);
}