Class AStarIterator
- Object
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- AbstractGraphIterator
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- SourceGraphIterator
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- AStarIterator
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- All Implemented Interfaces:
GraphIterator
public class AStarIterator extends SourceGraphIterator
A path iterator that uses a function (usually denoted f(x)) to determine the order in which the algorithm visits nodes, f(x) is a sum of two functions:- The path-cost function (usually denoted g(x), which may or may not be a heuristic)
- An admissible "heuristic estimate" (usually denoted h(x)).
// COST(n,n') : the real cost to go from n to n' OPEN = [Source] CLOSE = [] while ( |OPEN| > 0 ) n = a node in OPEN with less f remove n from OPEN add n to CLOSE if ( n == target ) { return // path find // if n != target for each node n' that relates to n do if n' in OPEN if (g(n) + COST(n,n')) < g(n') g(n') = g(n) + COST(n,n') parent(n') = n else g(n') = g(n) + COST(n,n') parent(n') = n add n' to OPEN // end while
- Author:
- Germán E. Trouillet, Francisco G. Malbrán. Universidad Nacional de Córdoba (UNC)
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
AStarIterator.AStarFunctions
Defines the functions needed by A Star.static class
AStarIterator.AStarNode
Internal data structure used to track node costs, and parent nodes.
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Constructor Summary
Constructors Constructor Description AStarIterator(Node source, AStarIterator.AStarFunctions afuncs)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
cont(Graphable current, GraphTraversal traversal)
Makes a step of the A* algorithm.Node
getParent(Node n)
protected Iterator<?>
getRelated(Graphable current)
void
init(Graph graph, GraphTraversal traversal)
Does Nothing.void
killBranch(Graphable current, GraphTraversal traversal)
Kills the branch of the traversalGraphable
next(GraphTraversal traversal)
Returns the next node in the priority queue. if the queue is empty then there is no path from the source to the destiny in this graph.-
Methods inherited from class SourceGraphIterator
getSource, setSource
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Methods inherited from class AbstractGraphIterator
getGraph, getTraversal, getWalker, setTraversal
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Constructor Detail
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AStarIterator
public AStarIterator(Node source, AStarIterator.AStarFunctions afuncs)
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Method Detail
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init
public void init(Graph graph, GraphTraversal traversal)
Does Nothing. All the work was already done by the constructor.- Parameters:
graph
- The graph being whose components are being iterated over.
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next
public Graphable next(GraphTraversal traversal)
Returns the next node in the priority queue. if the queue is empty then there is no path from the source to the destiny in this graph.- Returns:
- The next component in the iteration, or null if iteration is complete.
- See Also:
org.geotools.graph.traverse.GraphIterator#next()
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cont
public void cont(Graphable current, GraphTraversal traversal)
Makes a step of the A* algorithm. Takes the current node, looks for its neighbours. The ones which are closed are discarted. The ones "in" the opened queue are checked to see if its necessary to update them. The rest of the nodes are initialized as AStarNodes and inserted in the opened queue.- Parameters:
current
- The current component of the traversal.- See Also:
org.geotools.graph.traverse.GraphIterator#cont(Graphable)
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killBranch
public void killBranch(Graphable current, GraphTraversal traversal)
Kills the branch of the traversal- Parameters:
current
- The current component of the traversal.- See Also:
org.geotools.graph.traverse.GraphIterator#killBranch(Graphable)
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