Module org.jgrapht.unimi.dsi
Package org.jgrapht.webgraph

Class ImmutableUndirectedGraphAdapter

java.lang.Object
org.jgrapht.graph.AbstractGraph<Integer,E>
org.jgrapht.webgraph.AbstractImmutableGraphAdapter<it.unimi.dsi.fastutil.ints.IntIntSortedPair>
org.jgrapht.webgraph.ImmutableUndirectedGraphAdapter
All Implemented Interfaces:
it.unimi.dsi.lang.FlyweightPrototype<ImmutableUndirectedGraphAdapter>, Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
public class ImmutableUndirectedGraphAdapter extends AbstractImmutableGraphAdapter<it.unimi.dsi.fastutil.ints.IntIntSortedPair> implements it.unimi.dsi.lang.FlyweightPrototype<ImmutableUndirectedGraphAdapter>
An adapter class for undirected graphs using WebGraph's ImmutableGraph.

Nodes are instances of Integer corresponding to the index of a node in WebGraph. Edges are represented by an IntIntSortedPair. Edges are canonicalized so that the left element is always smaller than or equal to the right element. Since the underlying graph is immutable, the resulting graph is unmodifiable. Edges are immutable and can be tested for equality (e.g., stored in a dictionary).

You need to load a symmetric ImmutableGraph using one of the available load methods available, and then build an adapter: 

 immutableGraph = ImmutableGraph.loadMapped("mygraph");
 adapter = new ImmutableUndirectedGraphAdapter(immutableGraph);

It is your responsibility that the provided graph is symmetric (for each arc x → y there is an arc y → x). No check will be performed, but you can use the Check class to this purpose. Note that computing the number of edges of a graph requires a full scan of the edge set if ImmutableGraph.numArcs() is not supported (the first time—then it will be cached).

If you use a load method that does not provide random access, most methods will throw an UnsupportedOperationException.

If necessary, you can adapt a big WebGraph graph with at most Integer.MAX_VALUE vertices using the suitable wrapper.

Thread safety

This class is not thread safe: following the FlyweightPrototype pattern, users can access concurrently the graph by getting lightweight copies.

Fast adjacency check

As it happens for the sparse representation of JGraphT, usually a WebGraph compressed representation requires scanning the adjacency list of a node to test whether a specific arc exists. However, if you adapt a WebGraph class (such as EFGraph) which provides skippable iterators with fast skipping, adjacency can be tested more quickly (e.g., essentially in constant time in the case of EFGraph).

Author:
Sebastiano Vigna
See Also:

  • Constructor Details

    • ImmutableUndirectedGraphAdapter

      public ImmutableUndirectedGraphAdapter(it.unimi.dsi.webgraph.ImmutableGraph immutableGraph)
      Creates an adapter for an undirected (i.e., symmetric) immutable graph.

      It is responsibility of the caller that the provided graph has is symmetric (for each arc x → y there is an arc y → x). If this property is not true, results will be unpredictable.

      Parameters:
      immutableGraph - a symmetric immutable graph.

  • Method Details

    • makeEdge

      protected it.unimi.dsi.fastutil.ints.IntIntSortedPair makeEdge(int x, int y)
      Specified by:
      makeEdge in class AbstractImmutableGraphAdapter<it.unimi.dsi.fastutil.ints.IntIntSortedPair>

    • containsEdge

      public boolean containsEdge(it.unimi.dsi.fastutil.ints.IntIntSortedPair e)
      Description copied from interface: Graph
      Returns true if this graph contains the specified edge. More formally, returns true if and only if this graph contains an edge e2 such that e.equals(e2). If the specified edge is null returns false.
      Specified by:
      containsEdge in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      e - edge whose presence in this graph is to be tested.
      Returns:
      true if this graph contains the specified edge.

    • edgeSet

      public Set<it.unimi.dsi.fastutil.ints.IntIntSortedPair> edgeSet()
      Description copied from interface: Graph
      Returns a set of the edges contained in this graph. The set is backed by the graph, so changes to the graph are reflected in the set. If the graph is modified while an iteration over the set is in progress, the results of the iteration are undefined.

      The graph implementation may maintain a particular set ordering (e.g. via LinkedHashSet) for deterministic iteration, but this is not required. It is the responsibility of callers who rely on this behavior to only use graph implementations which support it.

      Specified by:
      edgeSet in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Returns:
      a set of the edges contained in this graph.

    • degreeOf

      public int degreeOf(Integer vertex)
      Description copied from interface: Graph
      Returns the degree of the specified vertex.

      A degree of a vertex in an undirected graph is the number of edges touching that vertex. Edges with same source and target vertices (self-loops) are counted twice.

      In directed graphs this method returns the sum of the "in degree" and the "out degree".

      Specified by:
      degreeOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - vertex whose degree is to be calculated.
      Returns:
      the degree of the specified vertex.

    • edgesOf

      public Set<it.unimi.dsi.fastutil.ints.IntIntSortedPair> edgesOf(Integer vertex)
      Description copied from interface: Graph
      Returns a set of all edges touching the specified vertex. If no edges are touching the specified vertex returns an empty set.
      Specified by:
      edgesOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - the vertex for which a set of touching edges is to be returned.
      Returns:
      a set of all edges touching the specified vertex.

    • inDegreeOf

      public int inDegreeOf(Integer vertex)
      Description copied from interface: Graph
      Returns the "in degree" of the specified vertex.

      The "in degree" of a vertex in a directed graph is the number of inward directed edges from that vertex. See http://mathworld.wolfram.com/Indegree.html.

      In the case of undirected graphs this method returns the number of edges touching the vertex. Edges with same source and target vertices (self-loops) are counted twice.

      Specified by:
      inDegreeOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - vertex whose degree is to be calculated.
      Returns:
      the degree of the specified vertex.

    • incomingEdgesOf

      public Set<it.unimi.dsi.fastutil.ints.IntIntSortedPair> incomingEdgesOf(Integer vertex)
      Description copied from interface: Graph
      Returns a set of all edges incoming into the specified vertex.

      In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

      Specified by:
      incomingEdgesOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - the vertex for which the list of incoming edges to be returned.
      Returns:
      a set of all edges incoming into the specified vertex.

    • outDegreeOf

      public int outDegreeOf(Integer vertex)
      Description copied from interface: Graph
      Returns the "out degree" of the specified vertex.

      The "out degree" of a vertex in a directed graph is the number of outward directed edges from that vertex. See http://mathworld.wolfram.com/Outdegree.html.

      In the case of undirected graphs this method returns the number of edges touching the vertex. Edges with same source and target vertices (self-loops) are counted twice.

      Specified by:
      outDegreeOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - vertex whose degree is to be calculated.
      Returns:
      the degree of the specified vertex.

    • outgoingEdgesOf

      public Set<it.unimi.dsi.fastutil.ints.IntIntSortedPair> outgoingEdgesOf(Integer vertex)
      Description copied from interface: Graph
      Returns a set of all edges outgoing from the specified vertex.

      In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

      Specified by:
      outgoingEdgesOf in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Parameters:
      vertex - the vertex for which the list of outgoing edges to be returned.
      Returns:
      a set of all edges outgoing from the specified vertex.

    • getType

      public GraphType getType()
      Description copied from interface: Graph
      Get the graph type. The graph type can be used to query for additional metadata such as whether the graph supports directed or undirected edges, self-loops, multiple (parallel) edges, weights, etc.
      Specified by:
      getType in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Returns:
      the graph type

    • copy

      public ImmutableUndirectedGraphAdapter copy()
      Specified by:
      copy in interface it.unimi.dsi.lang.FlyweightPrototype<ImmutableUndirectedGraphAdapter>

    • iterables

      public GraphIterables<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair> iterables()
      Description copied from interface: Graph
      Access the graph using the GraphIterables interface. This allows accessing graphs without the restrictions imposed by 32-bit arithmetic. Moreover, graph implementations are free to implement this interface without explicitly materializing intermediate results.
      Specified by:
      iterables in interface Graph<Integer,it.unimi.dsi.fastutil.ints.IntIntSortedPair>
      Returns:
      the graph iterables