Package it.unimi.dsi.webgraph

Class UnionImmutableGraph

java.lang.Object
it.unimi.dsi.webgraph.ImmutableGraph
it.unimi.dsi.webgraph.UnionImmutableGraph
All Implemented Interfaces:
FlyweightPrototype<ImmutableGraph>
public class UnionImmutableGraph
extends ImmutableGraph
An immutable graph representing the union of two given graphs. Here by “union” we mean that an arc will belong to the union iff it belongs to at least one of the two graphs (the number of nodes of the union is taken to be the maximum among the number of nodes of each graph).

  • Constructor Details

  • Method Details

    • copy

      public UnionImmutableGraph copy()
      Description copied from class: ImmutableGraph
      Returns a flyweight copy of this immutable graph.
      Specified by:
      copy in interface FlyweightPrototype<ImmutableGraph>
      Specified by:
      copy in class ImmutableGraph
      Returns:
      a flyweight copy of this immutable graph.
      See Also:
      FlyweightPrototype

    • nodeIterator

      public NodeIterator nodeIterator​(int from)
      Description copied from class: ImmutableGraph
      Returns a node iterator for scanning the graph sequentially, starting from the given node.

      This implementation just calls the random-access methods (ImmutableGraph.successors(int) and ImmutableGraph.outdegree(int)). More specific implementations may choose to maintain some extra state to make the enumeration more efficient.

      Overrides:
      nodeIterator in class ImmutableGraph
      Parameters:
      from - the node from which the iterator will iterate.
      Returns:
      a NodeIterator for accessing nodes and successors sequentially.

    • numNodes

      public int numNodes()
      Description copied from class: ImmutableGraph
      Returns the number of nodes of this graph.

      Albeit this method is not optional, it is allowed that this method throws an UnsupportedOperationException if this graph has never been entirely traversed using a node iterator. This apparently bizarre behaviour is necessary to support implementations as ArcListASCIIGraph, which do not know the actual number of nodes until a traversal has been completed.

      Specified by:
      numNodes in class ImmutableGraph
      Returns:
      the number of nodes.

    • randomAccess

      public boolean randomAccess()
      Description copied from class: ImmutableGraph
      Checks whether this graph provides random access to successor lists.
      Specified by:
      randomAccess in class ImmutableGraph
      Returns:
      true if this graph provides random access to successor lists.

    • hasCopiableIterators

      public boolean hasCopiableIterators()
      Description copied from class: ImmutableGraph
      Whether the node iterators returned by this graph support NodeIterator.copy(int).

      This implementation just returns ImmutableGraph.randomAccess().

      Overrides:
      hasCopiableIterators in class ImmutableGraph
      Returns:
      true if this graph provides copiable iterators.

    • successorArray

      public int[] successorArray​(int x)
      Description copied from class: ImmutableGraph
      Returns a reference to an array containing the successors of a given node.

      The returned array may contain more entries than the outdegree of x. However, only those with indices from 0 (inclusive) to the outdegree of x (exclusive) contain valid data.

      This implementation just unwraps the iterator returned by ImmutableGraph.successors(int). Subclasses are encouraged to override this implementation.

      Warning: all implementations must guarantee that a distinct array is returned for each node. The caller, in turn, must treat the array as a read-only object.

      Overrides:
      successorArray in class ImmutableGraph
      Parameters:
      x - a node.
      Returns:
      an array whose first elements are the successors of the node; the array must not be modified by the caller.

    • outdegree

      public int outdegree​(int x)
      Description copied from class: ImmutableGraph
      Returns the outdegree of a node.
      Specified by:
      outdegree in class ImmutableGraph
      Parameters:
      x - a node.
      Returns:
      the outdegree of the given node.