private SearchState(BitSet deletionMask, int currentIndex, SemanticGraph tree, string lastDeletedEdge, ForwardEntailerSearchProblem.SearchState source, double score)
{
this.deletionMask = (BitSet)deletionMask.Clone();
this.currentIndex = currentIndex;
this.tree = tree;
this.lastDeletedEdge = lastDeletedEdge;
this.source = source;
this.score = score;
}
/// <summary>Backtrace from a search state, collecting all of the deleted edges used to get there.</summary>
/// <param name="state">The final search state.</param>
/// <param name="justDeleted">The edges we have just deleted.</param>
/// <param name="otherEdges">Other deletions we want to register</param>
/// <returns>A list of deleted edges for that search state.</returns>
private static IList <string> AggregateDeletedEdges(ForwardEntailerSearchProblem.SearchState state, IEnumerable <SemanticGraphEdge> justDeleted, IEnumerable <string> otherEdges)
{
IList <string> rtn = new List <string>();
foreach (SemanticGraphEdge edge in justDeleted)
{
rtn.Add(edge.GetRelation().ToString());
}
foreach (string edge_1 in otherEdges)
{
rtn.Add(edge_1);
}
while (state != null)
{
if (state.lastDeletedEdge != null)
{
rtn.Add(state.lastDeletedEdge);
}
state = state.source;
}
return(rtn);
}
/// <summary>The search algorithm, starting with a full sentence and iteratively shortening it to its entailed sentences.</summary>
/// <returns>A list of search results, corresponding to shortenings of the sentence.</returns>
private IList <ForwardEntailerSearchProblem.SearchResult> SearchImplementation()
{
// Pre-process the tree
SemanticGraph parseTree = new SemanticGraph(this.parseTree);
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(parseTree));
// (remove common determiners)
IList <string> determinerRemovals = new List <string>();
parseTree.GetLeafVertices().Stream().Filter(null).ForEach(null);
// (cut conj_and nodes)
ICollection <SemanticGraphEdge> andsToAdd = new HashSet <SemanticGraphEdge>();
foreach (IndexedWord vertex in parseTree.VertexSet())
{
if (parseTree.InDegree(vertex) > 1)
{
SemanticGraphEdge conjAnd = null;
foreach (SemanticGraphEdge edge in parseTree.IncomingEdgeIterable(vertex))
{
if ("conj:and".Equals(edge.GetRelation().ToString()))
{
conjAnd = edge;
}
}
if (conjAnd != null)
{
parseTree.RemoveEdge(conjAnd);
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(parseTree));
andsToAdd.Add(conjAnd);
}
}
}
// Clean the tree
Edu.Stanford.Nlp.Naturalli.Util.CleanTree(parseTree);
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(parseTree));
// Find the subject / object split
// This takes max O(n^2) time, expected O(n*log(n)) time.
// Optimal is O(n), but I'm too lazy to implement it.
BitSet isSubject = new BitSet(256);
foreach (IndexedWord vertex_1 in parseTree.VertexSet())
{
// Search up the tree for a subj node; if found, mark that vertex as a subject.
IEnumerator <SemanticGraphEdge> incomingEdges = parseTree.IncomingEdgeIterator(vertex_1);
SemanticGraphEdge edge = null;
if (incomingEdges.MoveNext())
{
edge = incomingEdges.Current;
}
int numIters = 0;
while (edge != null)
{
if (edge.GetRelation().ToString().EndsWith("subj"))
{
System.Diagnostics.Debug.Assert(vertex_1.Index() > 0);
isSubject.Set(vertex_1.Index() - 1);
break;
}
incomingEdges = parseTree.IncomingEdgeIterator(edge.GetGovernor());
if (incomingEdges.MoveNext())
{
edge = incomingEdges.Current;
}
else
{
edge = null;
}
numIters += 1;
if (numIters > 100)
{
// log.error("tree has apparent depth > 100");
return(Java.Util.Collections.EmptyList);
}
}
}
// Outputs
IList <ForwardEntailerSearchProblem.SearchResult> results = new List <ForwardEntailerSearchProblem.SearchResult>();
if (!determinerRemovals.IsEmpty())
{
if (andsToAdd.IsEmpty())
{
double score = Math.Pow(weights.DeletionProbability("det"), (double)determinerRemovals.Count);
System.Diagnostics.Debug.Assert(!double.IsNaN(score));
System.Diagnostics.Debug.Assert(!double.IsInfinite(score));
results.Add(new ForwardEntailerSearchProblem.SearchResult(parseTree, determinerRemovals, score));
}
else
{
SemanticGraph treeWithAnds = new SemanticGraph(parseTree);
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(treeWithAnds));
foreach (SemanticGraphEdge and in andsToAdd)
{
treeWithAnds.AddEdge(and.GetGovernor(), and.GetDependent(), and.GetRelation(), double.NegativeInfinity, false);
}
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(treeWithAnds));
results.Add(new ForwardEntailerSearchProblem.SearchResult(treeWithAnds, determinerRemovals, Math.Pow(weights.DeletionProbability("det"), (double)determinerRemovals.Count)));
}
}
// Initialize the search
System.Diagnostics.Debug.Assert(Edu.Stanford.Nlp.Naturalli.Util.IsTree(parseTree));
IList <IndexedWord> topologicalVertices;
try
{
topologicalVertices = parseTree.TopologicalSort();
}
catch (InvalidOperationException)
{
// log.info("Could not topologically sort the vertices! Using left-to-right traversal.");
topologicalVertices = parseTree.VertexListSorted();
}
if (topologicalVertices.IsEmpty())
{
return(results);
}
Stack <ForwardEntailerSearchProblem.SearchState> fringe = new Stack <ForwardEntailerSearchProblem.SearchState>();
fringe.Push(new ForwardEntailerSearchProblem.SearchState(new BitSet(256), 0, parseTree, null, null, 1.0));
// Start the search
int numTicks = 0;
while (!fringe.IsEmpty())
{
// Overhead with popping a node.
if (numTicks >= maxTicks)
{
return(results);
}
numTicks += 1;
if (results.Count >= maxResults)
{
return(results);
}
ForwardEntailerSearchProblem.SearchState state = fringe.Pop();
System.Diagnostics.Debug.Assert(state.score > 0.0);
IndexedWord currentWord = topologicalVertices[state.currentIndex];
// Push the case where we don't delete
int nextIndex = state.currentIndex + 1;
int numIters = 0;
while (nextIndex < topologicalVertices.Count)
{
IndexedWord nextWord = topologicalVertices[nextIndex];
System.Diagnostics.Debug.Assert(nextWord.Index() > 0);
if (!state.deletionMask.Get(nextWord.Index() - 1))
{
fringe.Push(new ForwardEntailerSearchProblem.SearchState(state.deletionMask, nextIndex, state.tree, null, state, state.score));
break;
}
else
{
nextIndex += 1;
}
numIters += 1;
if (numIters > 10000)
{
// log.error("logic error (apparent infinite loop); returning");
return(results);
}
}
// Check if we can delete this subtree
bool canDelete = !state.tree.GetFirstRoot().Equals(currentWord);
foreach (SemanticGraphEdge edge in state.tree.IncomingEdgeIterable(currentWord))
{
if ("CD".Equals(edge.GetGovernor().Tag()))
{
canDelete = false;
}
else
{
// Get token information
CoreLabel token = edge.GetDependent().BackingLabel();
OperatorSpec @operator;
NaturalLogicRelation lexicalRelation;
Polarity tokenPolarity = token.Get(typeof(NaturalLogicAnnotations.PolarityAnnotation));
if (tokenPolarity == null)
{
tokenPolarity = Polarity.Default;
}
// Get the relation for this deletion
if ((@operator = token.Get(typeof(NaturalLogicAnnotations.OperatorAnnotation))) != null)
{
lexicalRelation = @operator.instance.deleteRelation;
}
else
{
System.Diagnostics.Debug.Assert(edge.GetDependent().Index() > 0);
lexicalRelation = NaturalLogicRelation.ForDependencyDeletion(edge.GetRelation().ToString(), isSubject.Get(edge.GetDependent().Index() - 1));
}
NaturalLogicRelation projectedRelation = tokenPolarity.ProjectLexicalRelation(lexicalRelation);
// Make sure this is a valid entailment
if (!projectedRelation.ApplyToTruthValue(truthOfPremise).IsTrue())
{
canDelete = false;
}
}
}
if (canDelete)
{
// Register the deletion
Lazy <Pair <SemanticGraph, BitSet> > treeWithDeletionsAndNewMask = Lazy.Of(null);
// Compute the score of the sentence
double newScore = state.score;
foreach (SemanticGraphEdge edge_1 in state.tree.IncomingEdgeIterable(currentWord))
{
double multiplier = weights.DeletionProbability(edge_1, state.tree.OutgoingEdgeIterable(edge_1.GetGovernor()));
System.Diagnostics.Debug.Assert(!double.IsNaN(multiplier));
System.Diagnostics.Debug.Assert(!double.IsInfinite(multiplier));
newScore *= multiplier;
}
// Register the result
if (newScore > 0.0)
{
SemanticGraph resultTree = new SemanticGraph(treeWithDeletionsAndNewMask.Get().first);
andsToAdd.Stream().Filter(null).ForEach(null);
results.Add(new ForwardEntailerSearchProblem.SearchResult(resultTree, AggregateDeletedEdges(state, state.tree.IncomingEdgeIterable(currentWord), determinerRemovals), newScore));
// Push the state with this subtree deleted
nextIndex = state.currentIndex + 1;
numIters = 0;
while (nextIndex < topologicalVertices.Count)
{
IndexedWord nextWord = topologicalVertices[nextIndex];
BitSet newMask = treeWithDeletionsAndNewMask.Get().second;
SemanticGraph treeWithDeletions = treeWithDeletionsAndNewMask.Get().first;
if (!newMask.Get(nextWord.Index() - 1))
{
System.Diagnostics.Debug.Assert(treeWithDeletions.ContainsVertex(topologicalVertices[nextIndex]));
fringe.Push(new ForwardEntailerSearchProblem.SearchState(newMask, nextIndex, treeWithDeletions, null, state, newScore));
break;
}
else
{
nextIndex += 1;
}
numIters += 1;
if (numIters > 10000)
{
// log.error("logic error (apparent infinite loop); returning");
return(results);
}
}
}
}
}
// Return
return(results);
}