private void MakeStep(int Pos, HMM State, int ArrayStateIndex)
{
double PrevMaxStateValue = 0;
string PrevStateName = "";
for (int I = 0; I < m_WorkingStates.Count; I++)
{
HMM PrevState = (Pos == 1) ? m_BeginingState : m_WorkingStates[I];
double PrevStateValue = Results[Pos - 1, I].Possibility *
PrevState.GetTransitionStrength(State.Name);
if (PrevStateValue > PrevMaxStateValue)
{
PrevMaxStateValue = PrevStateValue;
PrevStateName = PrevState.Name;
}
}
double Emission =
(Pos == m_Sequence.Count + 1) ?
1 : State.GetEmmisionStrength(m_Sequence[Pos - 1].Sequence);
Results[Pos, ArrayStateIndex] = new ViterbiResult(
Pos, State.Name, PrevStateName, Emission * PrevMaxStateValue);
}
private double CalcForwardState(HMM Hmm, int SeqPos)
{
double Result = 0;
int State = 0;
double[] LogSums = new double[m_WorkingStatesQty];
double EmmisionStr = 1; // for endingState
if (SeqPos < m_Sequence.Count)
EmmisionStr = Hmm.GetEmmisionStrength(m_Sequence[SeqPos].Sequence);
foreach(HMM HmmKm1 in m_WorkingStates)
{
// explog trick
LogSums[State] = Math.Log(EmmisionStr) +
Math.Log(HmmKm1.GetTransitionStrength(Hmm.Name)) +
Math.Log(ForwardValues[SeqPos,State]); // seqpos - 1 + 1 to shift for begining state
State++;
}
double MaxVal = LogSums[0];
for(int I = 1; I < m_WorkingStatesQty; I++)
MaxVal = Math.Max(MaxVal,LogSums[I]);
for(int I = 0; I < m_WorkingStatesQty; I++)
Result += Math.Exp(MaxVal + Math.Log(Math.Exp(LogSums[I] - MaxVal)));
return Result;
}