public Words Convert(WordGraph.T wg)
{
RunViterbiFwd(wg);
var words = RunViterbiBwd(wg);
return(words);
}
// calculate node probs and set prev flags
void RunViterbiFwd(WordGraph.T wg)
{
foreach (var p in wg.EndLocMap.Skip(1) /* skips BOS */)
{
var endIdx = p.Key;
foreach (var nd in p.Value)
{
var wordLen = nd.Word.Chars == Const.EOS ? 1 : nd.Word.Reading.Length;
var begIdx = endIdx - wordLen + 1;
var prevs = wg.EndLocMap[begIdx - 1];
// find prev node w/ the best value
WordGraph.Node bestNd = null;
double bestVal = double.MinValue;
foreach (var prev in prevs)
{
var curr = nd;
var prob = CalcProb(curr.Word, prev.Word);
var val = prev.Val + prob;
if (val > bestVal)
{
bestVal = val;
bestNd = prev;
}
}
nd.Prev = bestNd;
nd.Val = bestVal;
}
}
}
Words RunViterbiBwd(WordGraph.T wg)
{
var nd = wg.Eos;
var xs = new LinkedList <Word>();
while (nd != wg.Bos)
{
xs.AddFirst(nd.Word);
nd = nd.Prev;
}
xs.RemoveLast();
return(new Words {
Xs = xs.ToArray()
});
}
public Result <Words> ConvertByBigram(WordGraph.T wg)
{
return(Try(() => bigram.Convert(wg)));
}
