Module org.jgrapht.core
Package org.jgrapht.alg.shortestpath

Class DijkstraManyToManyShortestPaths<V,E>

java.lang.Object
org.jgrapht.alg.shortestpath.DijkstraManyToManyShortestPaths<V,E>
Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
ManyToManyShortestPathsAlgorithm<V,E>, ShortestPathAlgorithm<V,E>
public class DijkstraManyToManyShortestPaths<V,E> extends Object
Naive algorithm for many-to-many shortest paths problem using DijkstraClosestFirstIterator.

Complexity of the algorithm is $O(min(|S|,|T|)*(V\log V + E))$, where $S$ is the set of source vertices, $T$ is the set of target vertices, $V$ is the set of graph vertices and $E$ is the set of graph edges of the graph.

For each source vertex a single source shortest paths search is performed, which is stopped as soon as all target vertices are reached. Shortest paths trees are constructed using DijkstraClosestFirstIterator. In case $|T| > |S|$ the searches are performed on the reversed graph using $|T|$ as source vertices and $|S|$ as target vertices. This allows to reduce the total number of searches from $|S|$ to $min(|S|,|T|)$.

The main bottleneck of this algorithm is the memory usage to store individual shortest paths trees for every source vertex, as they may take a lot of space. Considering this, the typical use case of this algorithm are small graphs or large graphs with small total number of source and target vertices.

Author:
Semen Chudakov
See Also:

  • Field Details

    • graph

      protected final Graph<V,E> graph

  • Constructor Details

    • DijkstraManyToManyShortestPaths

      public DijkstraManyToManyShortestPaths(Graph<V,E> graph)
      Constructs an instance of the algorithm for a given graph.
      Parameters:
      graph - underlying graph

  • Method Details

    • getManyToManyPaths

      public ManyToManyShortestPathsAlgorithm.ManyToManyShortestPaths<V,E> getManyToManyPaths(Set<V> sources, Set<V> targets)
      Computes shortest paths from all vertices in sources to all vertices in targets.
      Parameters:
      sources - list of sources vertices
      targets - list of target vertices
      Returns:
      computed shortest paths

    • getPath

      public GraphPath<V,E> getPath(V source, V sink)
      Get a shortest path from a source vertex to a sink vertex.
      Specified by:
      getPath in interface ShortestPathAlgorithm<V,E>
      Parameters:
      source - the source vertex
      sink - the target vertex
      Returns:
      a shortest path or null if no path exists

    • getPathWeight

      public double getPathWeight(V source, V sink)
      Get the weight of the shortest path from a source vertex to a sink vertex. Returns Double.POSITIVE_INFINITY if no path exists.
      Specified by:
      getPathWeight in interface ShortestPathAlgorithm<V,E>
      Parameters:
      source - the source vertex
      sink - 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

    • getPaths

      public ShortestPathAlgorithm.SingleSourcePaths<V,E> getPaths(V source)
      Compute all shortest paths starting from a single source vertex.
      Specified by:
      getPaths in interface ShortestPathAlgorithm<V,E>
      Parameters:
      source - the source vertex
      Returns:
      the shortest paths

    • getShortestPathsTree

      protected static <V, E> ShortestPathAlgorithm.SingleSourcePaths<V,E> getShortestPathsTree(Graph<V,E> graph, V source, Set<V> targets)
      Computes shortest paths tree starting at source and stopping as soon as all of the targets are reached. Here the DijkstraClosestFirstIterator is used.
      Type Parameters:
      V - the graph vertex type
      E - the graph edge type
      Parameters:
      graph - a graph
      source - source vertex
      targets - target vertices
      Returns:
      shortest paths starting from source and reaching all targets