Voting Power

# Copyright (c) 2010, Panos Louridas, GRNET S.A.

#

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# list of conditions and the following disclaimer.

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use strict;

use Getopt::Long;

my $quorum = 1;

my $threshold = -1;

my $help = 0;

my $num_samples = 100000;

my $percentages = 0;

my $verbose = 0;

GetOptions("quorum=i" => \$quorum,

           "threshold=i" => \$threshold,

           "samples=i" =>\$num_samples,

           "percent" => \$percentages,

           "verbose" => \$verbose,

           "help" => \$help);

if ($help) {

    print <<HELP;

Usage: perl egi.voting.pl [OPTION] file

       Options are:

       -q, --quorum

            Set the quorum (number of voters required to reach decision)

       -s, --samples

            Set the number of samples

       -t, --threshold

            Set the threshold (amount of votes required to pass)

       -p, --percent

            Output results as percentages

       -v, --verbose

            Outputs group information (very large output)

       -h, --help

            Print this help screen

       file

            File containing the voter weights

HELP

    exit;

}

my %votes;

my %block_votes;

my $sum_votes = 0;

while (<>) {

    my ($voter, $voter_votes, $block_members) = split(/:/);

    $votes{$voter} = $voter_votes + 0;

    $sum_votes += $voter_votes;

    $block_votes{$voter} = $block_members ? $block_members + 0 : 1;

}

my @voters = keys(%votes);

$threshold = $sum_votes / 2 if $threshold = -1;

srand;

print "quorum voters: $quorum votes threshold: $threshold samples: $num_samples\n";

foreach my $voter (sort @voters) {

    my $voter_votes = $votes{$voter};

    my @voter_pool = keys(%votes);

    my $critical = 0;

    for (my $i = 0; $i < $num_samples; $i++) {

        my $member = 0;

        my $selection_size = 0;

        my @group;

        my $group_votes = 0;

        for my $candidate (@voter_pool) {

            if (rand(1) < 0.5) {

                push(@group, $candidate);

                $member = 1 if $candidate eq $voter;

                $selection_size += $block_votes{$candidate};

                $group_votes += $votes{$candidate};

            }

        }

        if ($member

            && ($group_votes >= $threshold)

            && (($group_votes - $voter_votes) < $threshold)

            && ($selection_size >= $quorum)) {

            $critical++;

            print "+ $selection_size @group $group_votes\n" if $verbose;

        } elsif (!$member

            && ($group_votes < $threshold)

            && (($group_votes + $voter_votes) >= $threshold)

            && (($selection_size + 1) >= $quorum)) {

            $critical++;

            print "- $selection_size @group $group_votes\n" if $verbose;

          } elsif ($verbose) {

            print "% $selection_size @group $group_votes\n";

          }

    }

    my $penrose = $critical / $num_samples;

    $penrose *= 100 if $percentages;

    print("$voter:$penrose\n");

}