Class BidirectionalAStarShortestPath<V,E>
- java.lang.Object
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- org.jgrapht.alg.shortestpath.BaseBidirectionalShortestPathAlgorithm<V,E>
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- org.jgrapht.alg.shortestpath.BidirectionalAStarShortestPath<V,E>
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- Type Parameters:
V
- the graph vertex typeE
- the graph edge type
- All Implemented Interfaces:
ShortestPathAlgorithm<V,E>
public class BidirectionalAStarShortestPath<V,E> extends BaseBidirectionalShortestPathAlgorithm<V,E>
A bidirectional version of A* algorithm.See the Wikipedia article for details and references about bidirectional search. This technique does not change the worst-case behavior of the algorithm but reduces, in some cases, the number of visited vertices in practice.
The algorithm was first introduced in Ira Sheldon Pohl. 1969. Bi-Directional and Heuristic Search in Path Problems. Ph.D. Dissertation. Stanford University, Stanford, CA, USA. AAI7001588.
The implementation uses two termination criteria depending on if the provided heuristic is consistent or not. Both criteria are based on the shortest path distance $\mu$ seen thus far in the search. Initially, in both cases the algorithm sets $\mu=\infty$. Whenever the search updates the information about the vertex $v$, it sets $\mu = min\{\mu; g_f(v) + g_b(v)\}$, where $g_f(v)$ is the current best-known path cost from $source$ to $sink$ and $g_b(v)$ is the current best-known path cost from $sink$ to $source$.
- Author:
- Semen Chudakov, Dimitrios Michail, Joris Kinable, Jon Robison, Thomas Breitbart
- See Also:
AStarShortestPath
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Nested Class Summary
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Nested classes/interfaces inherited from interface org.jgrapht.alg.interfaces.ShortestPathAlgorithm
ShortestPathAlgorithm.SingleSourcePaths<V,E>
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Field Summary
Fields Modifier and Type Field Description protected Graph<V,E>
graph
The underlying graph.protected static java.lang.String
GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE
Error message for reporting the existence of a negative-weight cycle.protected static java.lang.String
GRAPH_MUST_CONTAIN_THE_SINK_VERTEX
Error message for reporting that a sink vertex is missing.protected static java.lang.String
GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
Error message for reporting that a source vertex is missing.
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Constructor Summary
Constructors Constructor Description BidirectionalAStarShortestPath(Graph<V,E> graph, AStarAdmissibleHeuristic<V> heuristic)
Constructs a new instance of the algorithm for a given graph and heuristic.BidirectionalAStarShortestPath(Graph<V,E> graph, AStarAdmissibleHeuristic<V> heuristic, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,V>> heapSupplier)
Constructs a new instance of the algorithm for a given graph, heuristic and heap supplier.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected GraphPath<V,E>
createEmptyPath(V source, V sink)
Create an empty path.GraphPath<V,E>
getPath(V source, V sink)
Get a shortest path from a source vertex to a sink vertex.ShortestPathAlgorithm.SingleSourcePaths<V,E>
getPaths(V source)
Compute all shortest paths starting from a single source vertex.double
getPathWeight(V source, V sink)
Get the weight of the shortest path from a source vertex to a sink vertex.-
Methods inherited from class org.jgrapht.alg.shortestpath.BaseBidirectionalShortestPathAlgorithm
createPath
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Field Detail
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GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE
protected static final java.lang.String GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE
Error message for reporting the existence of a negative-weight cycle.- See Also:
- Constant Field Values
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GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
protected static final java.lang.String GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
Error message for reporting that a source vertex is missing.- See Also:
- Constant Field Values
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GRAPH_MUST_CONTAIN_THE_SINK_VERTEX
protected static final java.lang.String GRAPH_MUST_CONTAIN_THE_SINK_VERTEX
Error message for reporting that a sink vertex is missing.- See Also:
- Constant Field Values
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graph
protected final Graph<V,E> graph
The underlying graph.
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Constructor Detail
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BidirectionalAStarShortestPath
public BidirectionalAStarShortestPath(Graph<V,E> graph, AStarAdmissibleHeuristic<V> heuristic)
Constructs a new instance of the algorithm for a given graph and heuristic.- Parameters:
graph
- the graphheuristic
- heuristic that estimates distances between nodes
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BidirectionalAStarShortestPath
public BidirectionalAStarShortestPath(Graph<V,E> graph, AStarAdmissibleHeuristic<V> heuristic, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,V>> heapSupplier)
Constructs a new instance of the algorithm for a given graph, heuristic and heap supplier.- Parameters:
graph
- the graphheuristic
- heuristic that estimates distances between nodesheapSupplier
- supplier of the preferable heap implementation
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Method Detail
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getPath
public GraphPath<V,E> getPath(V source, V sink)
Get a shortest path from a source vertex to a sink vertex.- Parameters:
source
- the source vertexsink
- the target vertex- Returns:
- a shortest path or null if no path exists
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getPaths
public ShortestPathAlgorithm.SingleSourcePaths<V,E> getPaths(V source)
Compute all shortest paths starting from a single source vertex.- Specified by:
getPaths
in interfaceShortestPathAlgorithm<V,E>
- Parameters:
source
- the source vertex- Returns:
- the shortest paths
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getPathWeight
public double getPathWeight(V source, V sink)
Get the weight of the shortest path from a source vertex to a sink vertex. ReturnsDouble.POSITIVE_INFINITY
if no path exists.- Specified by:
getPathWeight
in interfaceShortestPathAlgorithm<V,E>
- Parameters:
source
- the source vertexsink
- the sink vertex- Returns:
- the weight of the shortest path from a source vertex to a sink vertex, or
Double.POSITIVE_INFINITY
if no path exists
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createEmptyPath
protected final GraphPath<V,E> createEmptyPath(V source, V sink)
Create an empty path. Returns null if the source vertex is different than the target vertex.- Parameters:
source
- the source vertexsink
- the sink vertex- Returns:
- an empty path or null null if the source vertex is different than the target vertex
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