//
// In order to provide a hint, we need to have:
// (1) the current problem
// (2) all of the steps entered thus far
//
// Algorithm:
// (a) Order the problem edges: least to greatest (they are by default)
// (b) Determine if any of the edges are complete and can deduce a new piece of information.
// (c) If no edge is complete, choose the node:
// (1) smallest node in an edge.
// (2) edge is more complete than any others.
// (3) node is not part of the problem givens
// (4) node is not part of the stepsTaken
//
public ConcreteAST.GroundedClause GetHint(ProblemAnalyzer.Problem <Hypergraph.EdgeAnnotation> problem,
List <ConcreteAST.GroundedClause> stepsTaken)
{
//
// Convert the stepsTaken into indices
//
List <int> takenIndices = new List <int>();
foreach (ConcreteAST.GroundedClause step in stepsTaken)
{
int index = Utilities.StructuralIndex(graph, step);
if (index != -1)
{
takenIndices.Add(index);
}
}
// Add the problem givens to the steps taken.
problem.givens.ForEach(g => takenIndices.Add(g));
int hintIndex = GetDeducibleEdgeTarget(problem, takenIndices);
if (hintIndex != -1)
{
return(graph.vertices[hintIndex].data);
}
hintIndex = GetClosestToCompleteEdge(problem, takenIndices);
if (hintIndex != -1)
{
return(graph.vertices[hintIndex].data);
}
return(null);
}
//
// For each edge, if all the source nodes are known, then return the target.
//
private int GetDeducibleEdgeTarget(ProblemAnalyzer.Problem <Hypergraph.EdgeAnnotation> problem, List <int> taken)
{
for (int edgeIndex = 0; edgeIndex < problem.edges.Count; edgeIndex++)
{
// Avoid edges, we have already deduced
if (!taken.Contains(problem.edges[edgeIndex].targetNode))
{
if (EdgeSourcesKnown(problem.edges[edgeIndex], taken))
{
return(problem.edges[edgeIndex].targetNode);
}
}
}
return(-1);
}
//
// For each edge, find the edge which is closest to knowing all sources, return the node with the least target.
//
private int GetClosestToCompleteEdge(ProblemAnalyzer.Problem <Hypergraph.EdgeAnnotation> problem, List <int> taken)
{
int minUnknownCount = int.MaxValue;
Pebbler.PebblerHyperEdge <Hypergraph.EdgeAnnotation> minUnknownEdge = null;
for (int edgeIndex = 0; edgeIndex < problem.edges.Count; edgeIndex++)
{
// Avoid edges, we have already deduced
if (!taken.Contains(problem.edges[edgeIndex].targetNode))
{
// Find minimal edge
int currUnknownCount = EdgeSourcesUnknownCount(problem.edges[edgeIndex], taken);
if (currUnknownCount < minUnknownCount) // Not <= since we want the earliest edge.
{
minUnknownCount = currUnknownCount;
minUnknownEdge = problem.edges[edgeIndex];
}
}
}
if (minUnknownEdge == null)
{
return(-1);
}
// Now that we know the minimum edge, find the minimum node in the edge that is unknown
foreach (int src in minUnknownEdge.sourceNodes)
{
if (!taken.Contains(src))
{
return(src);
}
}
return(-1);
}
//
// In order to provide a hint, we need to have:
// (1) the current problem
// (2) all of the steps entered thus far
//
public ConcreteAST.GroundedClause QueryHint(ProblemAnalyzer.Problem <Hypergraph.EdgeAnnotation> problem,
List <ConcreteAST.GroundedClause> stepsTaken)
{
return(hintGenerator.GetHint(problem, stepsTaken));
}
