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NAME
    Algorithm::PageRank::XS - A Fast PageRank implementation

DESCRIPTION
    This module implements a simple PageRank algorithm in C. The goal is to
    quickly get a vector that is closed to the eigenvector of the stochastic
    matrix of a graph.

    Algorithm::PageRank does some pagerank calculations, but it's slow and
    memory intensive. This module was developed to compute pagerank on
    graphs with millions of arcs. This module will not, however, scale up to
    quadrillions of arcs (see the TODO).

SYNOPSYS
        use Algorithm::PageRank::XS;

        my $pr = Algorithm::PageRank::XS->new();

        $pr->graph([
                  'John'  => 'Joey',
                  'John'  => 'James',
                  'Joey'  => 'John',
                  'James' => 'Joey',
                  ]
                  );

        $pr->result();
        # {
        #      'James' => '0.569840431213379',
        #      'Joey'  => '1',
        #      'John'  => '0.754877686500549'
        # }



        #
        #
        # The following simple program takes up arcs and prints the ranks.
        use Algorithm::PageRank::XS;

        my $pr = Algorithm::PageRank::XS->new();

        while (<>) {
            chomp;
            my ($from, to) = split(/\t/, $_);
            $pr->add_arc($from, $to);
        }

        my $r = $pr->results();
        while (my ($name, $rank) = each(%{$r})) {
            print "$name,$rank\n";
        }

METHODS
  new %PARAMS
    Create a new PageRank object. Possible parameters:

    alpha
        This is (1 - how much people can move from one node to another
        unconnected one randomly). Decreasing this number makes convergence
        more likely, but brings us further from the true eigenvector.

    max_tries
        The maximum number of tries until we give up trying to achieve
        convergence.

    convergence
        The maximum number the difference between two subsequent vectors
        must be before we say we are "convergent enough". The convergence
        rate is the rate at which "alpha^t" goes to 0. Thus, if you set
        "alpha" to 0.85, and "convergence" to 0.000001, then you will need
        85 tries.

  add_arc
    Add an arc to the pagerank object before running the computation. The
    actual values don't matter. So you can run:

        $pr->add_arc("Apple", "Orange");

    and you mean that "Apple" links to "Orange".

  graph
    Add a graph, which is just an array of from, to combinations. This is
    equivalent to calling "add_arc" a bunch of times, but may be more
    convenient.

  from_file FILE
    This will load arcs from a file, whose lines contain: