/// <summary>
/// Returns the best sequence of outcomes based on model for this object.</summary>
/// <param name="numSequences">
/// The maximum number of sequences to be returned.
/// </param>
/// <param name="sequence">
/// The input sequence.
/// </param>
/// <param name="additionalContext">
/// An object[] of additional context. This is passed to the context generator blindly with the assumption that the context are appropiate.
/// </param>
/// <param name="minSequenceScore">
/// A lower bound on the score of a returned sequence.</param>
/// <returns>
/// An array of the top ranked sequences of outcomes.
/// </returns>
public virtual Sequence[] BestSequences(int numSequences, object[] sequence, object[] additionalContext, double minSequenceScore)
{
int sequenceCount = sequence.Length;
ListHeap<Sequence> previousHeap = new ListHeap<Sequence>(Size);
ListHeap<Sequence> nextHeap = new ListHeap<Sequence>(Size);
ListHeap<Sequence> tempHeap;
previousHeap.Add(new Sequence());
if (additionalContext == null)
{
additionalContext = mEmptyAdditionalContext;
}
for (int currentSequence = 0; currentSequence < sequenceCount; currentSequence++)
{
int sz = System.Math.Min(Size, previousHeap.Size);
int sc = 0;
for (; previousHeap.Size > 0 && sc < sz; sc++)
{
Sequence topSequence = previousHeap.Extract();
String[] outcomes = topSequence.Outcomes.ToArray();
String[] contexts = ContextGenerator.GetContext(currentSequence, sequence, outcomes, additionalContext);
double[] scores;
if (mContextsCache != null)
{
scores = (double[]) mContextsCache[contexts];
if (scores == null)
{
scores = Model.Evaluate(contexts, mProbabilities);
mContextsCache[contexts] = scores;
}
}
else
{
scores = Model.Evaluate(contexts, mProbabilities);
}
double[] tempScores = new double[scores.Length];
Array.Copy(scores, tempScores, scores.Length);
Array.Sort(tempScores);
double minimum = tempScores[System.Math.Max(0, scores.Length - Size)];
for (int currentScore = 0; currentScore < scores.Length; currentScore++)
{
if (scores[currentScore] < minimum)
{
continue; //only advance first "size" outcomes
}
string outcomeName = Model.GetOutcomeName(currentScore);
if (ValidSequence(currentSequence, sequence, outcomes, outcomeName))
{
Sequence newSequence = new Sequence(topSequence, outcomeName, scores[currentScore]);
if (newSequence.Score > minSequenceScore)
{
nextHeap.Add(newSequence);
}
}
}
if (nextHeap.Size == 0)
{//if no advanced sequences, advance all valid
for (int currentScore = 0; currentScore < scores.Length; currentScore++)
{
string outcomeName = Model.GetOutcomeName(currentScore);
if (ValidSequence(currentSequence, sequence, outcomes, outcomeName))
{
Sequence newSequence = new Sequence(topSequence, outcomeName, scores[currentScore]);
if (newSequence.Score > minSequenceScore)
{
nextHeap.Add(newSequence);
}
}
}
}
//nextHeap.Sort();
}
// make prev = next; and re-init next (we reuse existing prev set once we clear it)
previousHeap.Clear();
tempHeap = previousHeap;
previousHeap = nextHeap;
nextHeap = tempHeap;
}
int topSequenceCount = System.Math.Min(numSequences, previousHeap.Size);
Sequence[] topSequences = new Sequence[topSequenceCount];
int sequenceIndex = 0;
for (; sequenceIndex < topSequenceCount; sequenceIndex++)
{
topSequences[sequenceIndex] = (Sequence) previousHeap.Extract();
}
return topSequences;
}
/// <summary>
/// Finds the n most probable sequences.
/// </summary>
/// <param name="numSequences">The number sequences.</param>
/// <param name="sequence">The sequence.</param>
/// <param name="additionalContext">The additional context.</param>
/// <param name="minSequenceScore">The minimum sequence score.</param>
/// <param name="beamSearch">The beam search.</param>
/// <param name="validator">The validator.</param>
public Sequence[] BestSequences(int numSequences, T[] sequence, object[] additionalContext,
double minSequenceScore,
IBeamSearchContextGenerator <T> beamSearch, ISequenceValidator <T> validator)
{
IHeap <Sequence> prev = new ListHeap <Sequence>(size);
IHeap <Sequence> next = new ListHeap <Sequence>(size);
prev.Add(new Sequence());
if (additionalContext == null)
{
additionalContext = new object[] {}; // EMPTY_ADDITIONAL_CONTEXT
}
for (var i = 0; i < sequence.Length; i++)
{
var sz = Math.Min(size, prev.Size());
for (var sc = 0; prev.Size() > 0 && sc < sz; sc++)
{
var top = prev.Extract();
var tmpOutcomes = top.Outcomes;
var outcomes = tmpOutcomes.ToArray();
var contexts = beamSearch.GetContext(i, sequence, outcomes, additionalContext);
double[] scores;
if (contextsCache != null)
{
scores = (double[])contextsCache.Get(contexts);
if (scores == null)
{
scores = model.Eval(contexts, probs);
contextsCache.Put(contexts, scores);
}
}
else
{
scores = model.Eval(contexts, probs);
}
var tempScores = new double[scores.Length];
for (var c = 0; c < scores.Length; c++)
{
tempScores[c] = scores[c];
}
Array.Sort(tempScores);
var min = tempScores[Math.Max(0, scores.Length - size)];
for (var p = 0; p < scores.Length; p++)
{
if (scores[p] < min)
{
continue; //only advance first "size" outcomes
}
var outcome = model.GetOutcome(p);
if (validator.ValidSequence(i, sequence, outcomes, outcome))
{
var ns = new Sequence(top, outcome, scores[p]);
if (ns.Score > minSequenceScore)
{
next.Add(ns);
}
}
}
if (next.Size() == 0)
{
//if no advanced sequences, advance all valid
for (var p = 0; p < scores.Length; p++)
{
var outcome = model.GetOutcome(p);
if (validator.ValidSequence(i, sequence, outcomes, outcome))
{
var ns = new Sequence(top, outcome, scores[p]);
if (ns.Score > minSequenceScore)
{
next.Add(ns);
}
}
}
}
}
// make prev = next; and re-init next (we reuse existing prev set once we clear it)
prev.Clear();
var tmp = prev;
prev = next;
next = tmp;
}
var numSeq = Math.Min(numSequences, prev.Size());
var topSequences = new Sequence[numSeq];
for (var seqIndex = 0; seqIndex < numSeq; seqIndex++)
{
topSequences[seqIndex] = prev.Extract();
}
return(topSequences);
}
