/// <summary>
/// Initialize a sampling tree with an existing belief node
/// </summary>
/// <param name="n"></param>
/// <param name="sampleNumber"></param>
/// <param name="maxDepth"></param>
/// <param name="markovModel"></param>
public SamplingTree(BeliefNode n, MarkovModel markovModel, int sampleNumber, int maxDepth, float gama, float C)
{
// The root is an existing beliefNode, useful to conserve the previous explorations
Root = n;
_markovModel = markovModel;
for (int i = 0; i < sampleNumber; i++)
{
GrowTree(maxDepth, gama, C);
}
}
//
/// <summary>
/// Create the Sampling tree of potential events
/// </summary>
/// <param name="d">Actual distribution of states of the system</param>
/// <param name="sampleNumber">number of samples in the tree</param>
/// <param name="maxDepth">maximum depth for each branch</param>
/// <param name="markovModel">model</param>
public SamplingTree(Distribution <State> d, MarkovModel markovModel, int sampleNumber, int maxDepth, float gama, float C)
{
// The root is the given distribution
_markovModel = markovModel;
Root = new BeliefNode(d, null, null, markovModel);
for (int i = 0; i < sampleNumber; i++)
{
GrowTree(maxDepth, gama, C);
}
}
/// <summary>
/// Add a child node at the end of the children list
/// </summary>
/// <param name="childNode">Child node</param>
public void AddChild(BeliefNode childNode)
{
Children.Add(childNode);
}
//
/// <summary>
/// Create node representing an action
/// </summary>
/// <param name="action">Action</param>
/// <param name="n">Parent node</param>
public ActionNode(Action action, BeliefNode n) : base()
{
Action = action;
Parent = n;
Children = new List <BeliefNode>();
}
//
/// <summary>
/// Function that perform one exploration of the tree, and make it grow by a pair of action & belief nodes
/// </summary>
/// <param name="maxDepth"></param>
public void GrowTree(int maxDepth, float gama, float C)
{
BeliefNode beliefNode = Root;
Root.IncrementOccurrence();
// Explore the tree until it reaches the finish point or the number of iteration is too high
int depth = 1;
ActionNode actionNode;
Action action;
State state;
bool stocking = true;
while (depth < maxDepth & !beliefNode.IsTerminal())
{
// Pick a state in the belief of the actual belief node
state = beliefNode.Belief.GetNormalisedCopy().Draw();
// Draw the next action
action = beliefNode.DrawAction(state, stocking, C);
// If the new node is not in the children, it is added, else its occurrence is incremented
actionNode = beliefNode.SearchChildren(action);
if (actionNode == null)
{
actionNode = new ActionNode(action, beliefNode);
if (stocking)
{
beliefNode.AddChild(actionNode);
}
}
else
{
actionNode.IncrementOccurrence();
}
// Get a new state of the system
state = _markovModel.ApplyTransition(state, action).Draw();
Observation observation = _markovModel.GetAllObservations(state).Draw();
// If the new node is not in the children, it is added, else its occurrence is incremented
beliefNode = actionNode.SearchChildren(observation);
if (beliefNode == null)
{
beliefNode = new BeliefNode(observation, actionNode, _markovModel);
if (stocking)
{
actionNode.AddChild(beliefNode);
}
stocking = false;
}
else
{
beliefNode.IncrementOccurrence();
}
beliefNode.AddState(state);
depth++;
}
beliefNode.UpdateValue(gama);
}
