Module org.jgrapht.core
Package org.jgrapht.alg.interfaces

Interface AStarAdmissibleHeuristic<V>

Type Parameters:
V - vertex type
All Known Implementing Classes:
ALTAdmissibleHeuristic
public interface AStarAdmissibleHeuristic<V>
Interface for an admissible heuristic used in A* search.
Author:
Joris Kinable, Jon Robison, Thomas Breitbart

  • Method Summary

    Modifier and Type
    Method
    Description
    double
    getCostEstimate(V sourceVertex, V targetVertex)
    An admissible "heuristic estimate" of the distance from $x$, the sourceVertex, to the goal (usually denoted $h(x)$).
    default <E> boolean
    isConsistent(Graph<V,E> graph)
    Returns true if the heuristic is a consistent or monotone heuristic wrt the provided graph.

  • Method Details

    • getCostEstimate

      double getCostEstimate(V sourceVertex, V targetVertex)
      An admissible "heuristic estimate" of the distance from $x$, the sourceVertex, to the goal (usually denoted $h(x)$). This is the good guess function which must never overestimate the distance.
      Parameters:
      sourceVertex - the source vertex
      targetVertex - the target vertex
      Returns:
      an estimate of the distance from the source to the target vertex

    • isConsistent

      default <E> boolean isConsistent(Graph<V,E> graph)
      Returns true if the heuristic is a consistent or monotone heuristic wrt the provided graph. A heuristic is monotonic if its estimate is always less than or equal to the estimated distance from any neighboring vertex to the goal, plus the step cost of reaching that neighbor. For details, refer to https://en.wikipedia.org/wiki/Consistent_heuristic. In short, a heuristic is consistent iff h(u)≤ d(u,v)+h(v), for every edge $(u,v)$, where $d(u,v)$ is the weight of edge $(u,v)$ and $h(u)$ is the estimated cost to reach the target node from vertex u. Most natural admissible heuristics, such as Manhattan or Euclidean distance, are consistent heuristics.
      Type Parameters:
      E - graph edges type
      Parameters:
      graph - graph to test heuristic on
      Returns:
      true iff the heuristic is consistent wrt the graph, false otherwise