NAME
   "Graph::Undirected::Components::External" - Computes components of an
   undirected graph.

SYNOPSIS
     use Data::Dump qw(dump);
     use Log::Log4perl qw(:easy);
     use Graph::Undirected::Components::External;
     Log::Log4perl->easy_init ($WARN);
     my $componenter = Graph::Undirected::Components::External->new(outputFile => 'vertexCompId.txt', purgeSizeBytes => 5000);
     my $vertices = 10000;
     for (my $i = 0; $i < $vertices; $i++)
     {
       $componenter->add_edge (int rand $vertices, int rand $vertices);
     }
     dump $componenter->finish ();

DESCRIPTION
   "Graph::Undirected::Components::External" computes the components of an
   undirected graph limited only by the amount of free disk space. All
   errors, warnings, and informational messages are logged using
   Log::Log4perl.

CONSTRUCTOR
 "new"
   The method "new" creates an instance of
   "Graph::Undirected::Components::External" with the following parameters.

   "workingDirectory"
         workingDirectory => File::Temp::tempdir()

       "workingDirectory" is an optional parameter specifying the path to a
       directory that all temporary files are written to; the default is
       set using File::Temp::tempdir().

   "purgeSizeBytes"
         purgeSizeBytes => 1000000

       "purgeSizeBytes" is an optional parameter specifying the aggregate
       byte size that all the vertices added to the internal instance of
       Graph::Undirected::Components must exceed before its content is
       purged to disk. The optimal value depends on the total internal
       memory available.

   "purgeSizeVertices"
         purgeSizeVertices => undef

       "purgeSizeVertices" is an optional parameter specifying the total
       vertices added to the internal instance of
       Graph::Undirected::Components that must be exceed before its content
       is purged to disk. If "purgeSizeBytes" and "purgeSizeVertices" are
       both defined, then a purge occurs when either threshold is exceeded.

   "retainPercentage"
         retainPercentage => 0.10

       "retainPercentage" is an optional parameter specifying the
       percentage of the most recently used vertices to be retained in the
       internal instance of Graph::Undirected::Components when it is
       purged. If the edges of the graph are not added in a random order,
       caching some of the vertices can speedup the computation of the
       components.

   "outputFile"
         outputFile => ...

       "outputFile" is the path to the file that the
       "(vertex,component-id)" pairs are written to; the directory of the
       file should exist. An exception is thrown if "outputFile" is
       undefined or the file cannot be written to.

   "delimiter"
         delimiter => ','

       "delimiter" is the delimiter used to separate the vertices of an
       edge when they are written to temporary files. All vertices should
       be encoded so that they do not contain the delimiter, that is, it
       should be true that "index($vertex,$delimiter)==-1" for all
       vertices.

METHODS
 "add_edge (vertexA, vertexB)"
   The method "add_edge" updates the components of the graph using the edge
   "(vertexA, vertexB)".

   vertexA, vertexB
       The vertices of the edge "(vertexA, vertexB)" are Perl strings. If
       only "vertexA" is defined, then the edge "(vertexA, vertexA)" is
       added to the graph. The method always returns undef.

 "add_file"
   The method "add_file" adds all the edges in a file to the graph.

   fileOfEdges => ...
       "fileOfEdges" specifies the path to the file containing the edges to
       add. An exception is thrown if there are problems openning or
       reading the file.

   delimiter
       The edges are read from "fileOfEdges" using Text::CSV; "delimiter"
       must be to the delimiter used to separate the vertices of an edge in
       the file. The default is the value set with the "new" constructor.

 "finish"
   The method "finish" completes the computation of the connected
   components and writes the pairs "(vertex,component-id)" to the
   "outputFile". For each component "component-id" is the lexographical
   minimum of all the vertices in the component.

   No edges can be added to the graph after "finish" is called.

INSTALLATION
   Use CPAN to install the module and all its prerequisites:

     perl -MCPAN -e shell
     cpan[1]> install Graph::Undirected::Components

BUGS
   Please email bugs reports or feature requests to
   "[email protected]", or through the web
   interface at
   <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Graph-Undirected-Compone
   nts>. The author will be notified and you can be automatically notified
   of progress on the bug fix or feature request.

AUTHOR
    Jeff Kubina<[email protected]>

COPYRIGHT
   Copyright (c) 2009 Jeff Kubina. All rights reserved. This program is
   free software; you can redistribute it and/or modify it under the same
   terms as Perl itself.

   The full text of the license can be found in the LICENSE file included
   with this module.

KEYWORDS
   connected components, network, undirected graph

SEE ALSO
   Graph, Graph::Undirected::Components, Log::Log4perl, Sort::External

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