/// <summary>
/// Returns the specified number of parses or fewer for the specified tokens.
/// </summary>
/// <param name="tokens">A parse containing the tokens with a single parent node.</param>
/// <param name="numParses">The number of parses desired.</param>
/// <returns>The specified number of parses for the specified tokens.</returns>
/// <remarks>
/// The nodes within the returned parses are shared with other parses and therefore their
/// parent node references will not be consistent with their child node reference.
/// <see cref="SharpNL.Parser.Parse.Parent"/> can be used to make the parents consistent with a
/// particular parse, but subsequent calls to this property can invalidate the results of earlier
/// calls.
/// </remarks>
public Parse[] Parse(Parse tokens, int numParses)
{
if (createDerivationString)
{
tokens.Derivation = new StringBuilder();
}
odh.Clear();
ndh.Clear();
completeParses.Clear();
var derivationStage = 0; //derivation length
var maxDerivationLength = 2 * tokens.ChildCount + 3;
odh.Add(tokens);
Parse guess = null;
double minComplete = 2;
double bestComplete = -100000; //approximating -infinity/0 in ln domain
while (odh.Size() > 0 &&
(completeParses.Size() < M || odh.First().Probability < minComplete) &&
derivationStage < maxDerivationLength)
{
ndh = new ListHeap <Parse>(K);
var derivationRank = 0;
// foreach derivation
for (var pi = odh.GetEnumerator(); pi.MoveNext() && derivationRank < K; derivationRank++)
{
var tp = pi.Current;
//TODO: Need to look at this for K-best parsing cases
/*
* if (tp.getProb() < bestComplete) { //this parse and the ones which follow will never win, stop advancing.
* break;
* }
*/
if (guess == null && derivationStage == 2)
{
guess = tp;
}
#if DEBUG
if (debugOn)
{
Console.Out.WriteLine(derivationStage + " " + derivationRank + " " + tp.Probability);
Console.Out.WriteLine(tp.ToString());
Console.Out.WriteLine();
}
#endif
Parse[] nd;
if (derivationStage == 0)
{
nd = AdvanceTags(tp);
}
else if (derivationStage == 1)
{
nd = AdvanceChunks(tp, ndh.Size() < K ? bestComplete : ndh.Last().Probability);
}
else
{
// i > 1
nd = AdvanceParses(tp, Q);
}
if (nd != null)
{
for (int k = 0, kl = nd.Length; k < kl; k++)
{
if (nd[k].Complete)
{
AdvanceTop(nd[k]);
if (nd[k].Probability > bestComplete)
{
bestComplete = nd[k].Probability;
}
if (nd[k].Probability < minComplete)
{
minComplete = nd[k].Probability;
}
completeParses.Add(nd[k]);
}
else
{
ndh.Add(nd[k]);
}
}
}
else
{
if (ReportFailedParse)
{
Console.Error.WriteLine("Couldn't advance parse " + derivationStage + " stage " +
derivationRank + "!\n");
}
AdvanceTop(tp);
completeParses.Add(tp);
}
}
derivationStage++;
odh = ndh;
}
if (completeParses.Size() == 0)
{
if (ReportFailedParse)
{
Console.Error.WriteLine("Couldn't find parse for: " + tokens);
}
//Parse r = (Parse) odh.first();
//r.show();
//System.out.println();
return(new[] { guess });
}
if (numParses == 1)
{
return(new[] { completeParses.First() });
}
var topParses = new List <Parse>();
while (!completeParses.IsEmpty() && topParses.Count < numParses)
{
var tp = completeParses.Extract();
topParses.Add(tp);
//parses.remove(tp);
}
return(topParses.ToArray());
}