Package it.unimi.dsi.webgraph

Class ASCIIGraph

java.lang.Object
it.unimi.dsi.webgraph.ImmutableGraph
it.unimi.dsi.webgraph.ImmutableSequentialGraph
it.unimi.dsi.webgraph.ASCIIGraph
All Implemented Interfaces:
FlyweightPrototype<ImmutableGraph>
public class ASCIIGraph
extends ImmutableSequentialGraph
An ImmutableGraph that corresponds to graphs stored in a human-readable ASCII format where each line contains the list of successors of a given node.

The file format is as follows: the graph is stored in a file named basename.graph-txt. The first line contains the number of nodes, n. Then, n lines follow, the i-th line containing the successors of node i in increasing order (nodes are numbered from 0 to n−1). Successors are separated by a single space.

Contrarily to other classes, the load methods of this class do not always return instances of this class. In particular, loadOffline(CharSequence) and loadOnce(InputStream) will return an instance of this class for offline access. The instance will not provide random access, but sequential access will be backed by the original text file and only one array of successor will be loaded in core memory at any time.

The load(CharSequence) method, on the other hand, will return an instance of ArrayListMutableGraph built by copying an offline instance of this class.

Using ASCIIGraph to convert your data

A simple (albeit rather inefficient) way to import data into WebGraph is using ASCII graphs. Suppose you create the following file, named example.graph-txt: 

  2
  1
  0 1
Then, the command 
  java it.unimi.dsi.webgraph.BVGraph -g ASCIIGraph example bvexample
will produce a compressed graph in BVGraph format with basename bvexample. Even more convenient is the loadOnce(InputStream) method, which reads from an input stream an ASCII graph and exposes it for a single traversal. It can be used, for instance, with the main method of BVGraph to generate somehow an ASCII graph and store it in compressed form on the fly. The previous example could be then rewritten as 
  java it.unimi.dsi.webgraph.BVGraph -1 -g ASCIIGraph dummy bvexample <example.graph-txt

  • Constructor Details

    • ASCIIGraph

      protected ASCIIGraph​(java.lang.CharSequence graphFile) throws java.lang.NumberFormatException, java.io.IOException
      Throws:
      java.lang.NumberFormatException
      java.io.IOException

    • ASCIIGraph

      public ASCIIGraph​(java.io.InputStream is) throws java.lang.NumberFormatException, java.io.IOException
      Creates a read-once ASCII graph. Instances created using this constructor can be only accessed using a single call to nodeIterator(int).
      Parameters:
      is - an input stream containing an ASCII graph.
      Throws:
      java.lang.NumberFormatException
      java.io.IOException

  • Method Details

    • 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.

    • 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 ImmutableSequentialGraph
      Parameters:
      from - the node from which the iterator will iterate.
      Returns:
      a NodeIterator for accessing nodes and successors sequentially.

    • splitNodeIterators

      public NodeIterator[] splitNodeIterators​(int howMany)
      Description copied from class: ImmutableGraph
      Returns an array of node iterators, scanning each a portion of the nodes of a graph. Iterators are guaranteed to scan mutually disjoint sets of nodes, and every node is guaranteed to be scanned by one iterator.

      This is an optional operation. If implemented, though, the returned iterators must properly implement NodeIterator.copy(int).

      Overrides:
      splitNodeIterators in class ImmutableGraph
      Parameters:
      howMany - the number of iterators to be returned (at the end of the array, some of them may be empty).
      Returns:
      the required iterators.

    • loadSequential

      @Deprecated public static ImmutableGraph loadSequential​(java.lang.CharSequence basename) throws java.io.IOException
      Deprecated.
      Throws:
      java.io.IOException

    • loadSequential

      @Deprecated public static ASCIIGraph loadSequential​(java.lang.CharSequence basename, ProgressLogger unused) throws java.io.IOException
      Deprecated.
      Throws:
      java.io.IOException

    • loadOffline

      public static ASCIIGraph loadOffline​(java.lang.CharSequence basename) throws java.io.IOException
      Throws:
      java.io.IOException

    • loadOffline

      public static ASCIIGraph loadOffline​(java.lang.CharSequence basename, ProgressLogger unused) throws java.io.IOException
      Throws:
      java.io.IOException

    • loadMapped

      public static ASCIIGraph loadMapped​(java.lang.CharSequence basename) throws java.io.IOException
      Throws:
      java.io.IOException

    • loadMapped

      public static ASCIIGraph loadMapped​(java.lang.CharSequence basename, ProgressLogger unused) throws java.io.IOException
      Throws:
      java.io.IOException

    • loadOnce

      public static ASCIIGraph loadOnce​(java.io.InputStream is) throws java.io.IOException
      Throws:
      java.io.IOException

    • load

      public static ImmutableGraph load​(java.lang.CharSequence basename) throws java.io.IOException
      Throws:
      java.io.IOException

    • load

      public static ImmutableGraph load​(java.lang.CharSequence basename, ProgressLogger unused) throws java.io.IOException
      Throws:
      java.io.IOException

    • store

      public static void store​(ImmutableGraph graph, java.lang.CharSequence basename, ProgressLogger unused) throws java.io.IOException
      Throws:
      java.io.IOException

    • store

      public static void store​(ImmutableGraph graph, java.lang.CharSequence basename) throws java.io.IOException
      Throws:
      java.io.IOException

    • store

      public static void store​(ImmutableGraph graph, int shift, java.lang.CharSequence basename) throws java.io.IOException
      Throws:
      java.io.IOException

    • main

      public static void main​(java.lang.String[] args) throws java.lang.IllegalArgumentException, java.lang.SecurityException, java.lang.IllegalAccessException, java.lang.reflect.InvocationTargetException, java.lang.NoSuchMethodException, java.io.IOException, JSAPException, java.lang.ClassNotFoundException, java.lang.InstantiationException
      Throws:
      java.lang.IllegalArgumentException
      java.lang.SecurityException
      java.lang.IllegalAccessException
      java.lang.reflect.InvocationTargetException
      java.lang.NoSuchMethodException
      java.io.IOException
      JSAPException
      java.lang.ClassNotFoundException
      java.lang.InstantiationException