Package org.jgrapht.alg.shortestpath

Class IntVertexDijkstraShortestPath<E>

  • Type Parameters:
    E - the graph edge type
    All Implemented Interfaces:
    ShortestPathAlgorithm<java.lang.Integer,​E>
    public final class IntVertexDijkstraShortestPath<E>
extends java.lang.Object
    Dijkstra Shortest Path implementation specialized for graphs with integer vertices.

    This class avoids using hash tables when the vertices are numbered from $0$ to $n-1$ where $n$ is the number of vertices of the graph. If vertices are not in this range, then they are mapped in this range using an open addressing hash table (linear probing).

    This implementation should be faster than our more generic one which is DijkstraShortestPath since it avoids the extensive use of hash tables.

    By default a 4-ary heap is used. The user is free to use a custom heap implementation during construction time. Regarding the choice of heap, it is generally known that it depends on the particular workload. For more details and experiments which can help someone make the choice, read the following paper: Larkin, Daniel H., Siddhartha Sen, and Robert E. Tarjan. "A back-to-basics empirical study of priority queues." 2014 Proceedings of the Sixteenth Workshop on Algorithm Engineering and Experiments (ALENEX). Society for Industrial and Applied Mathematics, 2014.

    Author:
    Dimitrios Michail

    • Field Detail

      • 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

      • 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

      • 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

      • graph

        protected final Graph<V,​E> graph
        The underlying graph.

    • Constructor Detail

      • IntVertexDijkstraShortestPath

        public IntVertexDijkstraShortestPath​(Graph<java.lang.Integer,​E> graph)
        Constructs a new instance of the algorithm for a given graph.
        Parameters:
        graph - the graph

      • IntVertexDijkstraShortestPath

        public IntVertexDijkstraShortestPath​(Graph<java.lang.Integer,​E> graph,
                                     java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,​java.lang.Integer>> heapSupplier)
        Constructs a new instance of the algorithm for a given graph.
        Parameters:
        graph - the graph
        heapSupplier - supplier of the preferable heap implementation

    • Method Detail

      • findPathBetween

        public static <E> GraphPath<java.lang.Integer,​E> findPathBetween​(Graph<java.lang.Integer,​E> graph,
                                                                       java.lang.Integer source,
                                                                       java.lang.Integer sink)
        Find a path between two vertices. For a more advanced search (e.g. using another heap), use the constructor instead.
        Type Parameters:
        E - the graph edge type
        Parameters:
        graph - the graph to be searched
        source - the vertex at which the path should start
        sink - the vertex at which the path should end
        Returns:
        a shortest path, or null if no path exists

      • getPath

        public GraphPath<java.lang.Integer,​E> getPath​(java.lang.Integer source,
                                                    java.lang.Integer sink)
        Description copied from interface: ShortestPathAlgorithm
        Get a shortest path from a source vertex to a sink vertex.
        Parameters:
        source - the source vertex
        sink - the target vertex
        Returns:
        a shortest path or null if no path exists

      • getPaths

        public ShortestPathAlgorithm.SingleSourcePaths<java.lang.Integer,​E> getPaths​(java.lang.Integer source)
        Compute all shortest paths starting from a single source vertex.

        Note that in the case of Dijkstra's algorithm it is more efficient to compute all single-source shortest paths using this method than repeatedly invoking getPath(Integer, Integer) for the same source but different sink vertex.

        Specified by:
        getPaths in interface ShortestPathAlgorithm<java.lang.Integer,​E>
        Parameters:
        source - the source vertex
        Returns:
        the shortest paths

      • 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

      • 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 vertex
        sink - the sink vertex
        Returns:
        an empty path or null null if the source vertex is different than the target vertex