/**
* /// Given a node, select a random successor from the set of possible successor nodes
*
* /// @param node the node
* /// @return a random successor node.
*/
private GrammarNode SelectRandomSuccessor(GrammarNode node)
{
GrammarArc[] arcs = node.GetSuccessors();
// select a transition arc with respect to the arc-probabilities (which are log and we don't have a logMath here
// which makes the implementation a little bit messy
if (arcs.Length > 1)
{
double[] linWeights = new double[arcs.Length];
double linWeightsSum = 0;
double EPS = 1E-10;
for (int i = 0; i < linWeights.Length; i++)
{
linWeights[i] = (arcs[0].Probability + EPS) / (arcs[i].Probability + EPS);
linWeightsSum += linWeights[i];
}
for (int i = 0; i < linWeights.Length; i++)
{
linWeights[i] /= linWeightsSum;
}
double selIndex = _randomizer.NextDouble();
int index = 0;
for (int i = 0; selIndex > EPS; i++)
{
index = i;
selIndex -= linWeights[i];
}
return(arcs[index].GrammarNode);
}
else
{
return(arcs[0].GrammarNode);
}
}
/**
* Retrieves the end node associated with the given node
*
* @param node the node of interest
* @return the ending node or null if no end node is available
*/
private GrammarNode GetEndNode(GrammarNode node)
{
GrammarArc[] arcs = node.GetSuccessors();
Debug.Assert(arcs != null && arcs.Length > 0);
return(arcs[0].GrammarNode);
}