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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
namespace Moserware.Skills.FactorGraphs
{
public abstract class Factor<TValue>
{
private readonly List<Message<TValue>> _Messages = new List<Message<TValue>>();
private readonly Dictionary<Message<TValue>, Variable<TValue>> _MessageToVariableBinding =
new Dictionary<Message<TValue>, Variable<TValue>>();
private readonly string _Name;
private readonly List<Variable<TValue>> _Variables = new List<Variable<TValue>>();
protected Factor(string name)
{
_Name = "Factor[" + name + "]";
}
/// Returns the log-normalization constant of that factor
public virtual double LogNormalization
{
get { return 0; }
}
/// Returns the number of messages that the factor has
public int NumberOfMessages
{
get { return _Messages.Count; }
}
protected ReadOnlyCollection<Variable<TValue>> Variables
{
get { return _Variables.AsReadOnly(); }
}
protected ReadOnlyCollection<Message<TValue>> Messages
{
get { return _Messages.AsReadOnly(); }
}
/// Update the message and marginal of the i-th variable that the factor is connected to
public virtual double UpdateMessage(int messageIndex)
{
Guard.ArgumentIsValidIndex(messageIndex, _Messages.Count, "messageIndex");
return UpdateMessage(_Messages[messageIndex], _MessageToVariableBinding[_Messages[messageIndex]]);
}
protected virtual double UpdateMessage(Message<TValue> message, Variable<TValue> variable)
{
throw new NotImplementedException();
}
/// Resets the marginal of the variables a factor is connected to
public virtual void ResetMarginals()
{
foreach (var currentVariable in _MessageToVariableBinding.Values)
{
currentVariable.ResetToPrior();
}
}
/// Sends the ith message to the marginal and returns the log-normalization constant
public virtual double SendMessage(int messageIndex)
{
Guard.ArgumentIsValidIndex(messageIndex, _Messages.Count, "messageIndex");
Message<TValue> message = _Messages[messageIndex];
Variable<TValue> variable = _MessageToVariableBinding[message];
return SendMessage(message, variable);
}
protected abstract double SendMessage(Message<TValue> message, Variable<TValue> variable);
public abstract Message<TValue> CreateVariableToMessageBinding(Variable<TValue> variable);
protected Message<TValue> CreateVariableToMessageBinding(Variable<TValue> variable, Message<TValue> message)
{
int index = _Messages.Count;
_Messages.Add(message);
_MessageToVariableBinding[message] = variable;
_Variables.Add(variable);
return message;
}
public override string ToString()
{
return _Name ?? base.ToString();
}
}
}
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