/// <summary>
/// Computes the total weights between each pair of states in the component
/// using the <a href="http://www.cs.nyu.edu/~mohri/pub/hwa.pdf">generalized Floyd's algorithm</a>.
/// </summary>
private void ComputePairwiseWeightsMatrix()
{
this.pairwiseWeights = Util.ArrayInit(this.Size, this.Size, (i, j) => Weight.Zero);
for (int srcStateIndexInComponent = 0; srcStateIndexInComponent < this.Size; ++srcStateIndexInComponent)
{
State state = this.statesInComponent[srcStateIndexInComponent];
foreach (var transition in state.Transitions)
{
State destState = state.Owner.States[transition.DestinationStateIndex];
int destStateIndexInComponent;
if (this.transitionFilter(transition) && (destStateIndexInComponent = this.GetIndexByState(destState)) != -1)
{
this.pairwiseWeights[srcStateIndexInComponent, destStateIndexInComponent] += transition.Weight;
}
}
}
for (int k = 0; k < this.Size; ++k)
{
Weight loopWeight =
this.useApproximateClosure ? Weight.ApproximateClosure(this.pairwiseWeights[k, k]) : Weight.Closure(this.pairwiseWeights[k, k]);
for (int i = 0; i < this.Size; ++i)
{
if (i == k || this.pairwiseWeights[i, k].IsZero)
{
continue;
}
for (int j = 0; j < this.Size; ++j)
{
if (j == k || this.pairwiseWeights[k, j].IsZero)
{
continue;
}
this.pairwiseWeights[i, j] += Weight.Product(
this.pairwiseWeights[i, k], loopWeight, this.pairwiseWeights[k, j]);
}
}
for (int i = 0; i < this.Size; ++i)
{
this.pairwiseWeights[i, k] *= loopWeight;
this.pairwiseWeights[k, i] *= loopWeight;
}
this.pairwiseWeights[k, k] = loopWeight;
}
}
/// <summary>
/// Initializes a new instance of the <see cref="EpsilonClosure"/> class.
/// </summary>
/// <param name="state">The state, which epsilon closure this instance will represent.</param>
internal EpsilonClosure(State state)
{
weightedStates = new List <(State, Weight)>(DefaultStateListCapacity);
// Optimize for a very common case: a single-node closure
bool singleNodeClosure = true;
Weight selfLoopWeight = Weight.Zero;
foreach (var transition in state.Transitions)
{
if (transition.IsEpsilon)
{
if (transition.DestinationStateIndex != state.Index)
{
singleNodeClosure = false;
break;
}
selfLoopWeight += transition.Weight;
}
}
if (singleNodeClosure)
{
Weight stateWeight = Weight.ApproximateClosure(selfLoopWeight);
this.weightedStates.Add((state, stateWeight));
this.EndWeight = stateWeight * state.EndWeight;
}
else
{
Condensation condensation = state.Owner.ComputeCondensation(state, tr => tr.IsEpsilon, true);
for (int i = 0; i < condensation.ComponentCount; ++i)
{
StronglyConnectedComponent component = condensation.GetComponent(i);
for (int j = 0; j < component.Size; ++j)
{
State componentState = component.GetStateByIndex(j);
this.weightedStates.Add((componentState, condensation.GetWeightFromRoot(componentState)));
}
}
this.EndWeight = condensation.GetWeightToEnd(state.Index);
}
}
/// <summary>
/// Gets the total weight between two given states in the component.
/// </summary>
/// <param name="srcStateIndexInComponent">The index of the source state in the component.</param>
/// <param name="destStateIndexInComponent">The index of the destination state in the component.</param>
/// <returns>The total weight between the given states in the component.</returns>
public Weight GetWeight(int srcStateIndexInComponent, int destStateIndexInComponent)
{
Argument.CheckIfInRange(
srcStateIndexInComponent >= 0 && srcStateIndexInComponent < this.Size,
nameof(srcStateIndexInComponent),
"The given index is out of range.");
Argument.CheckIfInRange(
destStateIndexInComponent >= 0 && destStateIndexInComponent < this.Size,
nameof(destStateIndexInComponent),
"The given index is out of range.");
if (this.Size == 1)
{
if (!this.singleStatePairwiseWeight.HasValue)
{
// Optimize for a common case
State state = this.statesInComponent[0];
this.singleStatePairwiseWeight = Weight.Zero;
foreach (var transition in state.Transitions)
{
if (this.transitionFilter(transition) && transition.DestinationStateIndex == state.Index)
{
this.singleStatePairwiseWeight += transition.Weight;
}
}
this.singleStatePairwiseWeight =
this.useApproximateClosure
? Weight.ApproximateClosure(this.singleStatePairwiseWeight.Value)
: Weight.Closure(this.singleStatePairwiseWeight.Value);
}
return(this.singleStatePairwiseWeight.Value);
}
if (this.pairwiseWeights == null)
{
this.ComputePairwiseWeightsMatrix();
}
return(this.pairwiseWeights[srcStateIndexInComponent, destStateIndexInComponent]);
}