public static void Viterbi(String Input, HMM HmmInput, StreamWriter Sw)
{
string[] words = Input.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries);
Double[,] Vertibi = new Double[HmmInput.statesList.Count + 2, words.Length + 2];
int[,] BackTrack = new int[HmmInput.statesList.Count + 2, words.Length + 2];
for (int i = 0; i < HmmInput.revStatesList.Count; i++)
{
double initProb = 0;
if (HmmInput.initBlock.ContainsKey(HmmInput.revStatesList[i]))
{
initProb = Math.Log10((HmmInput.initBlock[HmmInput.revStatesList[i]]) == 1.0 ? 0.99 : HmmInput.initBlock[HmmInput.revStatesList[i]]);
}
else
initProb = 0;
Vertibi[i, 0] = initProb;
BackTrack[i, 0] = -1;
}
double maxProb = int.MinValue, curProb, transProb = 0, emissionProb = 0;
string curTag, curword, prevTag, unknown = @"<unk>";
for (int t = 0; t < words.Length; t++)
{
curword = words[t];
for (int j = 0; j < HmmInput.revStatesList.Count; j++)
{
prevTag = HmmInput.revStatesList[j];
if (!HmmInput.TransitionBlock.ContainsKey(prevTag))
continue;
if (Vertibi[j, t] == 0.0)
continue;
foreach (var State in HmmInput.TransitionBlock[prevTag])
{
curTag = State.Key;
int i = HmmInput.statesList[curTag];
if (HmmInput.LogTransitionBlock.ContainsKey(prevTag) && HmmInput.LogTransitionBlock[prevTag].ContainsKey(curTag))
transProb = (HmmInput.LogTransitionBlock[prevTag])[curTag];
else
transProb = 0;
if (HmmInput.logEmissionBlock.ContainsKey(curTag) && HmmInput.logEmissionBlock[curTag].ContainsKey(curword))
emissionProb = (HmmInput.logEmissionBlock[curTag])[curword];
else if (!HmmInput.symbolList.ContainsKey(curword) && HmmInput.logEmissionBlock[curTag].ContainsKey(unknown))
emissionProb = (HmmInput.logEmissionBlock[curTag])[unknown];
else
emissionProb = 0;
if (transProb == 0 || emissionProb == 0)
curProb = int.MinValue;
else
curProb = Vertibi[j, t] + transProb + emissionProb;
if (Vertibi[i, t + 1] == 0.0 || curProb > Vertibi[i, t + 1])
{
Vertibi[i, t + 1] = curProb;
BackTrack[i, t + 1] = j;
}
}
}
}
//this gives the index from which we must start backtracking
int maxStateRowIndex = 0;
int wordIndex = words.Length ;
maxProb = int.MinValue;
for (int i = 0; i < HmmInput.revStatesList.Count; i++)
{
curProb = Vertibi[i, wordIndex];
if (curProb > maxProb)
{
maxStateRowIndex = i;
maxProb = curProb;
}
}
List<String> sb = new List<String>();
sb.Add(Convert.ToString(Vertibi[maxStateRowIndex, wordIndex]));
while (wordIndex > 0 && maxStateRowIndex >= 0)
{
sb.Add(HmmInput.revStatesList[maxStateRowIndex]);
maxStateRowIndex = BackTrack[maxStateRowIndex, wordIndex--];
}
sb.Add(" => ");
sb.Add(Input);
sb.Reverse();
var result = string.Join(" ", sb);
Sw.WriteLine(result);
}
static void Main(string[] args)
{
if (args.Length < 3)
throw new Exception("Incorect number of arguments");
string inputHmm = args[0];
string testFile = args[1];
string outputFile = args[2];
HMM HmmInput = new HMM();
HmmInput.validateFillHmm(inputHmm);
Stopwatch stopwatch = Stopwatch.StartNew();
String Input;
if (File.Exists(outputFile))
{
File.Delete(outputFile);
}
StreamWriter Sw = new StreamWriter(outputFile,true);
using (StreamReader Sr = new StreamReader(testFile))
{
while((Input=Sr.ReadLine())!=null)
{
Input = "<s> " + Input + " </s>";
if (String.IsNullOrWhiteSpace(Input))
continue;
Viterbi(Input, HmmInput,Sw);
}
}
Console.WriteLine("finished building the vertibi table : ");
Sw.Close();
stopwatch.Stop();
Console.WriteLine(stopwatch.ElapsedMilliseconds);
//Console.ReadLine();
}
