/// <summary>
/// For the List of Arc Calculate the Conjunctive value (min)
/// </summary>
/// <param name="voArcs">List of Arc</param>
/// <returns>Calculated Lambda</returns>
public float CalculateCombinedConjunctive(BeliefNode voBeliefNode, Arcs voArcs)
{
float fValue = float.MaxValue;
if (voArcs.InnerArcs != null)
{
foreach (Arcs arcs in voArcs.InnerArcs)
{
float fTest = EvaluateArcExpression(voBeliefNode, arcs);
fValue = (fValue <= fTest ? fValue : fTest);
}
}
foreach (Arc arc in voArcs.ArcList)
{
float fTest = CalculateEffectiveArcLambda(voBeliefNode, arc);
fValue = (fValue <= fTest ? fValue : fTest);
}
return fValue;
}
/// <summary>
/// Updates a single node in the Belief Net
/// </summary>
/// <param name="voBeliefNode">Belief Node</param>
/// <returns>True if node is updated, otherwise false</returns>
public bool UpdateNode(BeliefNode voBeliefNode)
{
voBeliefNode.EvaluatedArcExpression = EvaluateArcExpression(voBeliefNode, voBeliefNode.Arcs);
float fCurrentOdds = voBeliefNode.PriorOdds * voBeliefNode.EvaluatedArcExpression;
float fCurrentProbability = Utility.CalculateProbability(fCurrentOdds);
Console.Out.WriteLine(string.Format("Updated value of node {0} = {1}\n", voBeliefNode.Name, fCurrentProbability));
//voBeliefNode.PriorProbability = voBeliefNode.CurrentProbability;
voBeliefNode.CurrentProbability = fCurrentProbability;
return true;
}
/// <summary>
/// Returnes Updates for the Probability
/// </summary>
/// <param name="voBeliefNode">The BeliefNode</param>
/// <param name="voArc">Arc to Evaluate</param>
/// <returns>Updated Probability</returns>
public float UpdateProbability(BeliefNode voBeliefNode, Arc voArc)
{
BeliefNode arcNode = moNodes.GetBelief(voArc.Name);
float fUpdatedValue = 0.0f;
if (arcNode.CurrentProbability > arcNode.PriorProbability)
{
DebugProgress(voBeliefNode,voArc,arcNode,"Supporting arc");
fUpdatedValue = (float)(voBeliefNode.PriorProbability +
((Utility.CalculateProbability(voArc.Sufficiency * voBeliefNode.PriorOdds) - voBeliefNode.PriorProbability)
/
(1.0 - arcNode.PriorProbability) * (arcNode.CurrentProbability - arcNode.PriorProbability)));
}
else
{
DebugProgress(voBeliefNode, voArc, arcNode, "Inhibiting arc");
fUpdatedValue =
((Utility.CalculateProbability(voArc.Neccessity * voBeliefNode.PriorOdds)) +
(voBeliefNode.PriorProbability - Utility.CalculateProbability(voArc.Neccessity * voBeliefNode.PriorOdds))
/
arcNode.PriorProbability
*
arcNode.CurrentProbability);
}
return fUpdatedValue;
}
/// <summary>
/// Loads the nodes from Xml
/// </summary>
public void LoadXml(string vsFileName)
{
XmlTextReader reader = new XmlTextReader(vsFileName);
while (reader.Read())
{
switch (reader.Name)
{
case "Nodes":
break;
case "Node":
BeliefNode node = new BeliefNode(reader.ReadOuterXml());
moNodes.Add(node);
break;
}
}
}
/// <summary>
/// For a single Arc, this evalulate the expressions
/// </summary>
/// <param name="voArcs">Arcs</param>
/// <returns>Arc Expression</returns>
public float EvaluateArcExpression(BeliefNode voBeliefNode, Arcs voArcs)
{
switch (voArcs.ArcType)
{
case EnumArcType.Independent :
return CalculateCombinedIndependent(voBeliefNode, voArcs);
case EnumArcType.Conjunctive:
return CalculateCombinedConjunctive(voBeliefNode, voArcs);
case EnumArcType.Disjunctive :
return CalculateCombinedDisjunctive(voBeliefNode, voArcs);
default:
throw new Exception(string.Format("Invalid arc type {0}",voArcs.ArcType.ToString()));
}
}
/// <summary>
/// Debug Process, make sure values line up with LISP code
/// </summary>
/// <param name="voNode">Node we are updating</param>
/// <param name="voArc">current arc</param>
/// <param name="voArcNode">the arc node</param>
/// <param name="vsProgress">message</param>
public void DebugProgress(BeliefNode voNode, Arc voArc, BeliefNode voArcNode,string vsProgress)
{
Console.Out.WriteLine(string.Format("{0} update of {1} along arc ({2} {3} {4}) with prior odds {5}", vsProgress, voNode.Name, voArc.Name, voArc.Sufficiency, voArc.Neccessity, voNode.PriorOdds));
Console.Out.WriteLine(string.Format("The prior and current prob of E are {0}, {1}", voArcNode.PriorProbability, voArcNode.CurrentProbability));
}
/// <summary>
/// Calcualtes the Effective Arc Lambda
/// </summary>
/// <param name="voArc">Single Arc</param>
/// <returns>Calculate Lambda</returns>
public float CalculateEffectiveArcLambda(BeliefNode voBeliefNode, Arc voArc)
{
return Utility.CalculateOdds(UpdateProbability(voBeliefNode, voArc)) / voBeliefNode.PriorOdds;
}
/// <summary>
/// For the List of Arc Calculate the Combined Independent value
/// </summary>
/// <param name="voArcs">List of Arc</param>
/// <returns>Calculated Lambda</returns>
public float CalculateCombinedIndependent(BeliefNode voBeliefNode, Arcs voArcs)
{
float fCombined = 1.0f;
if (voArcs.InnerArcs != null)
{
foreach (Arcs arcs in voArcs.InnerArcs)
{
fCombined *= EvaluateArcExpression(voBeliefNode, arcs);
}
}
foreach (Arc arc in voArcs.ArcList)
{
fCombined *= CalculateEffectiveArcLambda(voBeliefNode, arc);
}
return fCombined;
}