public List <RandomVariable> ForwardBackward(List <string> perceptions)
{
RandomVariable[] forwardMessages = new RandomVariable[perceptions.Count + 1];
RandomVariable backwardMessage = priorDistribution.CreateUnitBelief();
RandomVariable[] smoothedBeliefs = new RandomVariable[perceptions.Count + 1];
forwardMessages[0] = priorDistribution;
smoothedBeliefs[0] = null;
// populate forward messages
for (int i = 0; i < perceptions.Count; i++) // N.B i starts at 1,
// not zero
{
forwardMessages[i + 1] = this.Forward(forwardMessages[i], perceptions[i]);
}
for (int i = perceptions.Count; i > 0; i--)
{
RandomVariable smoothed = priorDistribution.Duplicate();
smoothed.UpdateFrom(forwardMessages[i].AsMatrix().ArrayTimes(
backwardMessage.AsMatrix()));
smoothed.Normalize();
smoothedBeliefs[i] = smoothed;
backwardMessage = this.CalculateNextBackwardMessage(
forwardMessages[i], backwardMessage, perceptions[i - 1]);
}
return(smoothedBeliefs.ToList());
}