public ViterbiCalculator(IMLDataSet oseq, HiddenMarkovModel hmm)
{
if (oseq.Count < 1)
{
throw new EncogError("Must not have empty sequence");
}
this.delta = EngineArray.AllocateDouble2D((int)oseq.Count, hmm.StateCount);
this.psy = EngineArray.AllocateInt2D((int)oseq.Count, hmm.StateCount);
this._stateSequence = new int[oseq.Count];
for (int i = 0; i < hmm.StateCount; i++)
{
this.delta[0][i] = -Math.Log(hmm.GetPi(i))
- Math.Log(hmm.StateDistributions[i].Probability(
oseq[0]));
this.psy[0][i] = 0;
}
int t = 1;
for (int index = 1; index < oseq.Count; index++)
{
IMLDataPair observation = oseq[index];
for (int i = 0; i < hmm.StateCount; i++)
{
ComputeStep(hmm, observation, t, i);
}
t++;
}
this.lnProbability = Double.PositiveInfinity;
for (int i = 0; i < hmm.StateCount; i++)
{
double thisProbability = this.delta[oseq.Count - 1][i];
if (this.lnProbability > thisProbability)
{
this.lnProbability = thisProbability;
_stateSequence[oseq.Count - 1] = i;
}
}
this.lnProbability = -this.lnProbability;
for (int t2 = (int)(oseq.Count - 2); t2 >= 0; t2--)
{
_stateSequence[t2] = this.psy[t2 + 1][_stateSequence[t2 + 1]];
}
}
